In a house I own in Melbourne, Australia, I just replaced an old gas central heating system with 3 new top of the line Daikin mini split heat pumps. The new units can heat the entire house for the same amount of electrical energy that was used to run the FAN in the old gas unit. They are crazy efficient.
Ducts are dead.
The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units including installation. Payback time is about 3 years. The system is oversized, but enables excellent zoning and of course provides cooling which is a must on 40C/104F days.
Why do they seem to be so much more expensive in the US?
I don't think the hardware is that expensive in the US, it's the installation (which costs more than the hardware).
And mistakes by installers will cost even more. Our installers didn't flare a line set connection properly and it leaked slowly and that was a very expensive bill (especially since refrigerants have changed so much).
Our Daikin indoor units have also had condensate leaking issues, probably due to poor installation.
Ductless heat pumps do seem like the future but I think there are issues with regards to condensate draining, air filtering, and indoor unit cleaning/maintenance and replacement that could be done much better.
I love our Daikin mini-splits (came with the house), but as you allude to I've had to become an mini expert on deep cleaning them. They've can get GROSS with mold when used for cooling, and the cursory filter only does so much. That being said, now they stay clean for a few years after a deep cleaning -- though my first few attempt before I refined the process did not stay clean nearly as long. (Proper water pressure and disinfect is key.)
Cleaning basically involves a dedicated cover + drain that diverts water to a bucket, and blasting it with what's effectively a "low power pressure washer" I can use indoors (carefully), and "Lemocide" to properly disinfect... And coil cleaner for the fins. Takes me a good 4+ hours per unit, largely spent preparing the area in case there is any rogue spray. (Though TBH I may be a bit obsessive about getting it right.)
I also had a drain leak as you mentioned -- blasting the drain line with aforementioned "low pressure washer" helped with that. Still a bit gross to deal with. (And learning how to properly disassemble and clean the drip tray is the final thing I've put off leaning for a completely-thorough deep clean... I'm a bit horrified anticipating what I'll find...)
The no 1 reason I bought the Daikin model referenced over the comparable Mitsubishi Electric is that it has the ‘MOULD PROOF’ function. It runs the fan automatically after you have had it in cooling mode, to evaporate the moisture build up from the interior condenser coil, thereby removing the moisture required for the growth of bacteria and mould.
So far, it seems to be working! Better than relying on everyone to manually do it (literally this is the instruction in the Mitsubishi Electric user manual).
That definitely helps and I used to do that in my car where the A/C got smelly pretty quickly. Just run the "fan" for a few minutes after you turn off the A/C and it doesn't get gross.
But one problem is the dust in the house. It will collect on the unit and hold moisture and give a great substrate for mold to grow. But regular cleaning usually takes care of that.
If you live in any kind of area with high humidity you just shifted the mold from the AC unit to the rest of your house. Hell even here in the desert I'm not sure I'd want to use that "feature".
We are talking about the tiny amount of water vapour left on the interior condenser. The idea is to bring that back up to room temperature so that it doesn’t stay there near the dew point. The total amount of water inside the house does not change!
The surface of our planet is so rich in bio material that some tiny amount of mold can be found in almost all unfiltered air. Instead of trying to eliminate all of it, home builders focus on preventing it from growing. Indoors, mold often has everything it needs to grow except standing moisture, so it's important for everything to either dry out or circulate water.
I'd love to see a youtube video of your cleaning methodology.
Most of the videos from HVAC people are... sketchy to the say the least.
I've seen videos where they dismantle the whole indoor unit and leave the coil just hanging from the line set or zip tied to the backplate while they take the fan and drain pan outside to clean.
One easy thing we've found that helps with drain clogs is to use a shop vacuum from outside to suck it out (using a towel/rag to get a good pressure seal). Takes around 5 minutes per drain per cooling season.
I'll try recording something next time I clean one of the units (one needs a deep clean this spring); no promises though. In the meantime, here are some quick notes/resources.
- I cover the electronics in a garage bag held with tape. No need to unscrew the black cover over the power wires to disassemble (I unnecessarily removed this a few times heh).
- I ended up really liking this cleaning shrowd after trying a few; the hard pieces on the sides are key for making it easy to secure nicely, which many others lack: https://www.amazon.com/gp/aw/d/B083S85X97
- I spend more time (like 30min+) spraying the blower wheel so it spins. I alternate spraying with fresh water with spraying diluted "Lemocide" (@10% dilution) from a spray bottle a bunch of times depending how dirty it is. I use this <https://snowjoe.com/products/sun-joe-wa24c-lte-24v-150-psi-m...> which at 100 PSI is 10x stronger than a hand pump sprayer, but 10x weaker than a real pressure washer. I.e. the sweet spot IMO.
- I use foaming coil clean from a can to clean the fins if they're particularly dirty. (WARNING: I have not used in the same cleaning as the Lemocide since I haven't confirmed if they're compatible, so be careful of any reactions if you use both in the same cleaning.)
- I take the outer casings outside for a quick rinse with the hose and dish soap if they're really dusty.
- I tape cheap plastic mirrors at 45 degree angle above the unit so I can see it from above and carefully vacuum the back coil (there are 3 folded over in a U, and you can only see 2 from the front). Otherwise this just accumulates junk and is hard to see. This also really helps with finding the 3x clips at the top of the case that secure it to the back housing.
I may have a few more notes worth sharing at some point; feel free to ping me if you have any specific questions.
Edit: See also this quick video on unclogging the drain line on a Daikin (though I used the sprayer against the tube instead of my mouth...): https://m.youtube.com/watch?v=GDrHe-rli98
We also had a drainage problem after ours were installed. We were very fortunate that another, more experienced tech from the same company came by to follow up on a different issue and took it on themselves to inspect the drain line. It would have leaked into our wall for a long time before it became apparent something was wrong. These units (ours are also Daikin) are a dream to operate but you definitely need to triple-check the drainage on first run.
I once looked at a house with a new GSHP horizontal loop installed in the desert southwest US. I talked to the installer and they said the loop was only 12” deep. There’s no way the ground maintains steady temp at that depth, meaning you’re losing efficiency in the hot months when you need it most. Not to mention thermal pollution which will exacerbate the problem and the risk of hitting the loop with even minor ground work. They were adamant it was a good design.
Unfortunately, many installers jump on the bandwagon without the necessary expertise.
Yeah, I know it seems more likely that was a typo, but that's what they told me :) Tbf, roots, animals, and mowers probably aren't that big of an issue because it was mostly xeriscaped desert.
I take your point, but installation faults in central gas heating are also very common, but perhaps less obvious. The main one I’m thinking about is poor sealing or placement of the return duct, causing entrainment of air from the wall cavity. Source: local experts, and then I inspected my friend’s houses (hah).
Dealer salespeople are loyal to their brands and shit talk the other brands, so I'd take that with a grain of salt. I own both brands, they are basically the same.
Mitsubishi Electric or Mitsubishi Heavy Industries?
I sourced opinions far and wide and in the end it seemed to be a coin toss between Mitsubishi Electric and Daikin. A lot of it comes done to parts availability, and both seem very strong in Australia.
Both brands trade off as best cold weather heat pumps in ratings/evaluations (quick Google search should confirm), they’re both fairly high quality versus competitor brands.
Ducts are still needed to circulate air, especially if you want to remove stale air (e.g., bathrooms, kitchen) and bring in (filtered) fresh air (to bedrooms).
A recirculating central heating system doesn't do that. As mentioned below you either need exhaust only ventilation, balanced ventilation or ideally ERV/HRV. All of the above are available in both ducted and ductless forms.
A recirculation system will prevent high levels of CO2 buildup in occupied rooms, particularly with closed doors. I've measured the difference in our bedroom overnight between having the fan on and off, and it was dramatic (if I recall correctly, something like 700ppm in the morning vs 2000). Even if it's only keeping the level consistent throughout the house, that would be a benefit. But every house will have some amount of air leakage as well; a recirculation fan with a fresh air intake (which all modern ones have) will pull in fresh, filtered and conditioned air to replace air that leaks out. If that's not sufficient for indoor air quality, then you can crack a window or set an exhaust fan to run periodically. I haven't generally found that necessary though.
ERV/HRV has its place it less moderate climates where there is significant efficiency loss from pulling in outdoor air, especially if indoor conditions require a significant amount of fresh air turnover. But a central HVAC system with a recirculation fan most definitely can be beneficial in a lot of cases.
It’s worth noting that ASHRAE ventilation standards are based on “bioeffluence” levels which may or may not correlate well to other IAQ values like CO2, VOCs, etc.
I've seen that terminology used on US websites, it took me a while to get my head around. In Australia it would just be called ducted reverse cycle. In the vast majority of cases it would be "ducted ductless" I guess: outside unit connects via refrigerant lines to a heat exchanger and fan in the roof cavity, when then distributes the heated/cooled air to rooms via conventional ducting.
Nobody calls it that (ducted ductless), it would just be called a ducted heat pump. The refrigerant lines just run to a central air handler where the ducts start in the house, instead of the air handlers that mount on the walls.
If it's an existing build with ducts, stick with that. If it's a new build, then like the other poster said, you add more units. See the top of any commercial building for example: heat pumps all over the place.
Another option is to supplement an existing ducted system with a ductless one adding additional zones where you might want conditioning over night. E.g. bedrooms where you want to sleep in cold A/C in the summer where the rest of the house can warm up a bit, or a person in the household who likes their room to be warmer than everyone elses in the winter.
Not being snarky but why don't you just open the window for that?
I have a CO2 detector that I believe is a reasonable proxy for stale air. When it goes above 1000 I simply open the windows. By the time I remember to close the windows the reading is almost always below 500.
On the west coasts of Canada (BC) we've had insane forest fires the past few years and you 100% want to filter the internal air when it's extremely unhealthy outside. We're talking air quality index in the 300+ range or off the charts at times [1]. Plus, we've had these heat domes were it's in the high 30+ and just gross inside, where you really want to open the windows, but you're letting in tons of pollution. Basically, you need to cool off and filter the air at the same time.
This. We live <50’ from an expressway, so after air sealing and replacing all of our ducts, I added a MERV 16 filter to our air handler. We had the windows open at night a few years back (no ac as well), and I woke up to smell of smoke from a forest fire after the winds changed direction. AQI2.5 was 200+ inside. Closed windows, ran the fan on high and after a couple minutes the AQI throughout the house was within healthy range (tested multiple locations). Unfortunately our furnace model leaves few realistic options for controlling it programmatically, so I still have to manually turn on the fan when AQI drops.
I have a routine for this scenario: open the windows in the morning for 1-2 hours, then close everything and clean the air internally (I have a 24/7 sensor running and know when the air is good or bad).
That seemed like the easiest thing to do without making much more complicated system. Basically risk 1hour of bad air for 23h of "clean" air.
You want to open windows in opposite sides of the house to quickly circulate air from outside to inside. 5 minutes should be enough. It will get colder, but most of the heat is in walls and furnitures and as long as you only open the windows for a few minutes it should be quick to heat up the air again.
I don't know; is it more energy inefficient than having a fresh air intake via a duct? Maybe they are comparable in the absence of a heat recovery ventilation system (mentioned by a sibling comment upthread)?
HEPA and carbon filters do wonders for cooking smells, particulates etc, but unfortunately do nothing for the main reason you want air exchange with outside, which is CO2 buildup.
Seems like it would be more efficient to wear a climate controlled bubble suit than heating up entire rooms. And you could even go outside when it is cold or hot or dusty.
If it's pretty cold outside, then you're throwing all of the ostensible energy savings of a heat pump out the window the minute you open it to air out the house.
Following the thread of conversation, it just didn't compute to me:
>>>> Heat pumps are great for climate control
>>> Yeah, ducts are dead
>> What if you want to recirculate air in your house through your central air filter to eliminate smells?
> Just open the window
It's like we've hit a contraction: the premise is that we care about energy but the contractions is then that we don't and we open the window while climate controlling the house. So to me it does seem to prove that in some climates, duct work with a central blower and filter mat not be dead.
We've just today had our first snow of the season here in a lower elevation of the Sierra Foothills. It's been chilly for 3 months or so, and our heating is an 'old school' ducted propane furnace. In time, we'll replace it with a heat pump, but not this year. Anyway, we're sensitive to accumulated odors that go with a well insulated, closed-up home in winter.
Every evening, we open three doors in the house to the outside. This is after the furnace has entered its timed 'off for the night' state. We exchange pretty much all of our air for fresh ambient, which is great when we wake up in the morning.
The impact from doing this on our propane bill is undetectable. This is because air, even humid air, has a trivial heat capacity compared to the warm house structure and contents. Those are by far the greatest energy reservoir in our home. Very little energy is lost in a daily air exchange with the ambient.
I'm not sure why "Heat pumps are great for climate control" went to "ducts are dead".
I live in Florida, we've used Heat Pumps for as long as I can remember. We also have central air handlers with blowers and ducts to distribute the conditioned air. Mini-splits can _also_ be ducted mini-splits. According to my HVAC geek friend, mini-splits are pretty terrible about humidity control (an important thing in Florida). For proper humidity control you'd ideally have a dedicated set of dehumidification ducts (powered by a central dehumidifier) as well. Mix in an ERV and you have the ability to build a fairly air-tight house with _controlled_ ventilation and very efficient conditioning of the air in the house.
The Melbourne climate I was referring to needs heating 9 months of the year. The vast majority of houses have very simple, inefficient gas ducted heating. Rightly or wrongly, humidity control is generally not well considered.
I was going to install an ERV system but the payback was not within the life of the equipment.
Someday I’ll build a Passivhaus with a system as you describe.
No doubt: majority of the southern US went to heatpumps with central air handlers 2-3 decades ago. Ducts are definitely not dead. Or, if they're dead, then they must be as dead as BSD. :-P
Where I live, it can get very cold. Not always very efficient to open windows for 5 months out of the year.
A great option for keeping CO2 levels down in a house is with an HRV (or ERV) [1] that will heat the fresh air coming in to cycle it throughout the house.
> During the warmer seasons, an ERV system pre-cools and dehumidifies; During cooler seasons the system humidifies and pre-heats.[1] An ERV system helps HVAC design meet ventilation and energy standards (e.g., ASHRAE), improves indoor air quality and reduces total HVAC equipment capacity, thereby reducing energy consumption.
> ERV systems enable an HVAC system to maintain a 40-50% indoor relative humidity, essentially in all conditions. ERV's must use power for a blower to overcome the pressure drop in the system, hence incurring a slight energy demand.
In Jan 2023, the ERV wikipedia article has a 'Table of Energy recovery devices by Types of transfer supported': Total and Sensible :
IME you don't use an ERV alone. You'd use it _with_ a Heat Pump. The ERV is all about transferring heat from one airstream to another. It's _not_ a device that manages indoor temperatures though, just recovers some of the latent energy in the air. In the process it's also managing humidity mainly as a by-product. The humidification properties of the ERV allow you to run the Heat Pump in a more efficient manner. I have an HVAC geek friend who explained the whole process, but essentially (in non physics/fluid dynamics[?] terminology), if the Heat Pump doesn't need to dehumidify air it can operate more efficiently.
There is an open source 3D printable unit design here which I installed in my window and works well for relatively efficiently exhausting the CO2 from one person in cold weather: https://www.openerv.org (license: CC BY-NC-SA 3.0)
I did not 3D print mine, but ordered it, though as an early adopter, adjustment was required.
Do you know, is there a document explaining the design somewhere? I can see from the Google images some of the parts, but not clearly all the parts nor the flowpaths and such.
I used to have a bathroom without an extractor and in the winter with the window open the cold air would just cool the walls and cause more condensation there than I’d get with it closed.
I have a bathroom without an extractor. If I don't open the window the mirror fogs up in seconds of turning the shower on, and over time I get mould. If I do open the window it stays clear the entire time. By the time I'm out and dry the moist air has left and I close the window.
This morning it was -5C, so not cold by continental standards, but certainly cold enough.
In the UK recirculating air is very rare. In cases that bathrooms don't have a window (or indeed in new houses where they do) there's an extractor fan, but that just vents the air directly outside.
A ventilation system allows you to filter (not a luxury when you live in a big city, where you will be breathing pollutants otherwise) or perform some thermal magic if the outside air is very cold (or very warm), by running the outflow and inflow pipes really close to each other.
Part of it is code. Make-up air systems need a duct for example. Also a lot of people like their air filtered so opening a window isn’t great for that. Also winter.
The only requirement is "2 channel low drift NDIR gas sensor". Cheap CO2 detectors either have zero IR sensors (instead they guesstimate eCO2 using a VOC sensor) or a single IR sensor that requires weekly calibration outdoors or it will just assume that the lowest sensor reading means 400ppm.
They're obviously no replacement for exhaust fans in bathrooms and kitchens, but there's a number of ductless energy recovery ventilators that can give you fresh air in your bedroom(s).
Thank you - this could solve a problem in my house. We had CO2 build up in our bedrooms and the only way I have found to ameliorate the problem is to have our HVAC fan running continuously at night to circulate the air in our house.
In have ducted mini split units in my home, made by Mitsubishi I designed the system to work with merv 13-16 filters. I can run the fans and filter my air as well as use the units for heat and cooling. I installed fresh air intakes on the return units that can pull external air when they are opened.
It's really a very good proposition. Has all of the advantages of central heating and the efficiencies the heat pumps
Approximately 70% of the heat loss from your body is as radiated heat. Ceiling insulation is critical for thermal comfort. Have a look at the Efficiency Matrix YouTube channel videos on insulation consistency.
Less that 2% of insulation being out of place can waste something like 40% or some ridiculous amount of energy. It's quite nuts how even just a little break in insulation can have a significantly negative effect. A few years after I moved into my first home - a townhouse - I added some R-16 bats to the already existing R-12 insulation in the attic and it more than cut my heating bill in half. It was a three story narrow, townhouse - not that much square footage of ceiling compared to the walls/rest of the house but it made ALL the difference. If I didn't live it, I wouldn't have believed it. And I kind of did it on a whim since I didn't need that many and Lowes was having a sale on insulation. I would have done it the first week I moved in and had a couple far more comfortable winters!
It’s still a thermal path between inside and outside, and thus wastes energy if you’re trying to maintain an internal temperature that is different from the external temperature. Also there are radiative effects - hot spots on ceiling will radiate IR into your space. Just try standing under a corrugated steel roof in the summer.
Because in the winter the thermal energy within your room will “flow” out of those “cold spots” at surprisingly high rates; in summer those spots act as space heaters. In both scenarios they will adversely affect the ambient temp of the room. In short, whatever method you use to heat/cool the room will have to work harder and will take longer. Here’s [0] a good overview of heat flow in this context, with some hints towards the math behind if you wish to go deeper.
I read it as: Ducts are better but not so much that it's worth tearing everything apart to install them. If you don't already have ducts, you should definitely use a ductless system. If you do have them, you get some other benefits.
I think he means having a duct work for the whole house for a central heat pump is good. But having a heat pump per zone is also good if you don't have ducts for the whole house. Some newer home designs separate heating and cooling from the air exchange systems so there are multiple zones of heating and cooling.
It doesn't get that cold in most places in Australia does it?
Heat pumps need to be scaled for the maximum heating or cooling load, whichever is greater. The optimal situation is that the heating and cooling loads are similar, but in colder parts of the U.S. the heating load is much larger than the cooling load and the case for the heat pump is not so good as a place where the need for heating and cooling are more balanced.
We have a brand new Daikin VRV system in new york and are currently working on retrofitting a nat gas heating solution - heat pumps aren't a good fit for anywhere north of Atlanta:
When it's really cold out (say 25F or below), the heat pump stops for around 10mins to defrost the exterior coils, which means no heat running at all in that period, and this pause happens more frequently the colder it's outside. The end result, our ~1400 sq place took more than 24hrs to heat up from 55F to 72F when we got back after christmas.
Also you don't save any money on operating it, even with the efficiency yade yada the cost of electricity will run you more than the equivalent in nat gas. So nothing but downside.
In Melbourne’s climate where piped methane costs 1/3 per kWh that of electricity, but heat pumps are 300-500% efficient and you remove the duct loss, for most people their heating bill drops by 2/3. Add solar self consumption and you are way ahead.
My limited understanding of the defrost cycle is that it’s most a problem around 0c? If it’s a colder or warmer it doesn’t get triggered as often?
Great. You just eliminated approximately 15% of lazy screenwriter tropes for thrillers and action movies. Now they are forced to rely on replacing live surveillance camera feeds with a loop.
Are you asking why the Daikin Alira X is more expensive in the US? It's because it's not a brand that is normally found here.
If you went with a common US brand you can get a good system with 4 units and a 36,000 BTU heat pump unit for around $6,500 USD installed.
I don't love the wall units - they're pretty ugly, even the new ones. If you're getting a mini-split, the in-ceiling or wall cassettes that are hidden are really the way to go IMO.
Seems to just be Seattle tax, I had to get a water line replaced in my home and the quotes were $2-7k higher than I've seen suggested in other regions. Tradework here is inflated likely by the salaries of tech workers in the city.
In my locale, trades like plumbing (including gas & hvac), drywall, roofing etc range from 1 to 1.5 what contract developers from NTT, IBM et al are billed at. In absolute terms - 110 - 140 for contract devs and trades are often "to busy" at 170.
I got quoted 16 grand for the same 24k/3 zone system in the Seattle area by the guys who install thru COSTCO. I ordered the hardware myself for $4300, bought about $300 worth of tools, and installed it in one long weekend. It’s really not that difficult. Basic electric installation, some special technique and tools needed for the plumbing (University of Youtube can help), pressure test, pull vacuum, open the valves and enjoy.
This is the way. And don’t forget your refrigerant license, which is super easy/cheap to get. Some manufacturers will void your warranty if not installed by someone unlicensed.
The problem with Mr. Cool is that their DIY claim is because you don't cut the lineset (I believe they give you 25 ft). Any excess length you're supposed to coil up and hide, which is not ideal- plus you'll lose efficiency.
I believe they now sell other size lines and extensions.
I got hung up on the excess line set idea and did a full DIY install of a non-DIY model mini-split. I bought, borrowed, and rented a lot of tools, spent a lot of time researching and learning. I really wish I went with the DIY model.
Despite that lesson, I may do it again when I finish my attic space, but this time I'll add copper line brazing to the list.
No, not at all. I enjoyed it but my wife had a different expectation of completion date than I. My advice is to get the tools, don't shortcut, so that you have confidence at each step.
Stuff I had already specific to HVAC:
-R-410a manifold, gauges, and hoses.
Stuff I went out and bought:
-Nitrogen tank pressure regulator and hose for HVAC.
-Mandrel pipe bender
-Flaring tool
-Micron vacuum gauge
-A slightly better copper pipe cutter and deburring tool.
Stuff I rented/borrowed:
-Vacuum pump from Autozone. Free. It was plenty big enough for a minisplit.
-Full nitrogen cylinder rental from Airgas.
Things I'm glad I did:
-Used a wall mount instead of a pad for the compressor unit. Unit stays clean.
- Pressure testing with nitrogen. It's worth the money and effort to know up front it doesn't leak.
-Followed a more thorough procedure for vacuuming/drying which involves vacuuming down several times and flushing with nitrogen. I got a much better vacuum after subsequent flushes.
Thanks for the follow up! I understand completely. Somehow my wife stuck with me after more than a few significant home projects with misaligned expectations around completion. Re: wall mounting vs pad. Do you find noise transmission to be a nuisance?
I was on the lookout for it, as it was a concern of mine. I haven't noticed an issue. It's also mounted on an exterior wall of my garage. That wall lacks insulation but has drywall. It may be more of an issue if it shared a wall with a bedroom. The mount has rubber dampeners between the unit and the arms.
How do you get the pipes through the wall in a pre charged unit? Do they have two pieces connected by a special valve? I’m curious about how they keep the air out of the lines.
Pre-charge has one of two meanings here. Most mini-split units have the refrigerant in the compressor unit. After a complete installation, evacuation, etc, you open a valve to release the refrigerant into the lines.
There are also DIY variants where a fixed line length comes from the factory with either a vacuum or a refrigerant in the line. The lines have metal seals on the fittings that are ruptured when torqued down on the equipment.
In the Australian market, the efficiency of the in ceiling or in wall units is lower than the high wall units. They are also much cheaper to buy and install.
Same, and we have just implemented 2 x 7.1kw units along with about 7kwh solar panels. Our heating costs have plummeted and we can survive on days like today (17th Jan) with minimal impact to our comfort.
We are looking at changing water heating next as this is now the biggest part of our utility usage.
Regional Vic for me, Daikin Alira X's installed in rooms about a month or two ago, and they've been great. Very energy efficient, and individual units in each room means we can match everyone's preferred climate -- even heating one room while cooling another! Main downside is that you need space for more inverter units outside.
They're pretty quiet, too. You can certainly hear the air coming out, but it's fairly quiet and certainly wouldn't be noisy enough to bother you over tv, work, or anything else.
I got a similar setup for my house as well. Being able to selectively cool rooms that are in use is great. However, I do wish the insulation was far better. Unfortunately I’ve noticed that Melbourne houses are usually very poorly constructed due to expensive raw materials and labour.
Have you examined your insulation with a thermal camera? Might be worth your while to get an energy inspector out. Personally I haven’t yet, mostly because I can still see low hanging fruit to fix.
You don't even need a pro - you can get FLIR cameras that attach to cell phones for around $100 and they are more than adequate to show you areas of irregularity and worthy of targeting. I got one years ago mainly as just something to play with but I use it ALL the time for all kinds of things. Having a thermal camera is crazy useful.
Yea have some pretty obvious improvements pending as well. But that’s a good suggestion - might get someone to come give a professional assessment before I put in a 7kwh unit for another room.
Ducted heatpumps are a thing here in NZ and make sense to me, not that I have used one. The heatpump sits in the roof and air is pushed into three or so rooms through ducts.
If building a new house I think ducts would be the way to go.
You have to think carefully about where you run the ducts. They can be a huge source of energy loss. 40% is the number quoted by the EPA.
Most roofs in Australia still aren’t sealed. The air barrier and insulation barrier is the ceiling. The roof space itself is not insulated, so the ducts are exposed to extreme temperatures, thus destroying the efficiency.
My argument with split systems, at least how they are installed in NZ, is that they are usually installed in the main living area and if there is a second unit, in a corridor.
So corridors are heated or cooled far hotter or colder than they need to be in order to heat/cool bedrooms.
I have two units that are heated by heat pumps in Massachusetts.
One has mini splits. You definitely don’t generally put mini splits in every single room (like bathrooms or interior hallways) because each mini split requires tubing, is large, and expensive. No, I think it’s way more likely that you would have them in the bedrooms rather than the hallway
That might be a climate difference — it gets below 0 Fahrenheit here every winter, as I understand it, NZ is quite a bit warmer, so maybe the strategy of “heat the core of the house and let it radiate out” works.
US and Australian units are different for insulation, but in my terms the insulation around the best ducts is R1.5, but good ceiling insulation is R6. 4x difference
Edit: not to mention the huge difference in surface area. Ducts can expose your conditioned air to a huge, poorly insulated surface. Bad for efficiency.
Interesting. The code for duct insulation in unconditioned spaces in the US is R8, and they're pushing for higher currently.
They also recently undid a long held myth about ducts buried in insulation leading to condensation issues. Most areas now allow ducts to be buried as long as you have R19 above and below, or R30 above. When I just installed a ducted mini for 3 upstairs bedrooms, I surrounded my R8 flex duct with R30 insulation.
Fwiw, context of this video is metal duct work. You’re not going to see R-8 flex duct buried in R-30 begin to sweat when the AC is running. In terms of controlling the dew point, the duct is no different than the conditioned space at that point.
Your statement is quite context dependent, and does not apply to most modern residential scenarios. “Over insulating” a flex duct is not going to cause condensation.
Metal duct work in an unconditioned space can cause condensation. Wrapping it in (often thin) fiberglass insulation can increase condensation in certain conditions. Improperly vented attics (and/or air leakage from conditioned space) with metal ducts can cause issues.
I thought this was absolutely the solution but backtracking a little now based on experience so far.
We have a two-level, five bedroom new build in Auckland which came with a single-zone ducted system. So outputs are the bedrooms plus upstairs and downstairs lounges. The vents are tidy and unobtrusive - much less space than a wall unit in each location.
We're having major issues balancing the temperature across the different rooms as there is one thermostat.
Think setting the temperature overnight for one room with a couple plus a cat vs another room with one of the kids. Basically the wife and I are always far too hot because otherwise we're freezing all the other rooms. Or setting a reasonable temperature in the lounge makes all the rooms icy in short time.
I'm now thinking about forking out the couple of thousand to get a small heat pump installed directly into our room so we can run it separately from the rest of the house.
So if building from scratch, either look into a multi-zone system or separate heatpumps. If you can get separate systems but hidden in the walls/roof that would be the best.
I had a similar problem, but I decided that simply running the fan to mix up the air was a fine solution. The fan doesn't use much electricity, and it's good not to let rooms get too stale anyway.
I have the fan programmed to run 10 or 15 minutes an hour regardless of if the heat pump needs to run. It keeps things pretty even.
Have checked the ducts for dampers? They're often installed where the duct branches. It's not unusual to find they're not balanced well or the locking screws have loosened allowing the dampers to move on their own.
always good to have zoning, either via small separate heat pump or with a retrofit like AirZone (not sure if something similar is available there) which modulates the flow to each duct from the air handler.
The problem I have with mini splits is that they are an architectural eyesore. Are there any high quality ones designed to be built into walls discretely like cove lighting has done for lighting?
Ducts are good for indoor air quality though. Keeping our central fan on at low speed all the time significantly reduces measured CO2 in occupied rooms, particularly bedrooms overnight.
I am leaning more to this solution for this reason. Trying to get any tradie quickly these days doesn't happen. Trying to get an aircon person in an Australian summer is worse.
I despair for the rental market right now. High prices and landlords are generally crap at amenities they don't personally use.
Indeed, sounds like a problem with the fan. My 3000sf house uses 1100W for the fan, and about 4000W for the heat pump. I expect converting to mini-splits would increase, not decrease my overall power usage.
700W for the gas ducted heater fan. That’s the steady state energy consumption of all 3 units heat pumps running simultaneously. This is a small house of 100 square metres/1100 square feet.
I recently replaced my [central, ducted] heat pump, and the new one is rated with a 4.981 SCOP. It's fairly efficient, but not the most efficient on the market.
It would be nice to actually link the source[1] (PDF).
The stat is that you lose between 25-40% efficiency for "typical" existing installations. The document goes on to explain that an insulated duct which doesn't leak doesn't have this kind of efficiency loss.
Though mini split heads can be ducted too. There are several choices, wall heads, ceiling heads, ducted heads etc. The wall head is just the cheapest solution since it’s very easy to install.
They're noisy too. Not loud, it's a quiet hum, but it's annoying if that annoys you, some people are sensitive to noise. The system I have doesn't seem to have a variable-output control, so it uses an on/off hysteresis that drives me up the wall. I could deal with a constant hum, but the stop start every minute or two is annoying. A previous house I lived in the ducts were absolutely silent unless it was on high you could hear some airflow noise. They can be placed anywhere wall floor ceiling (depending on construction of course), and have a wide range of styles.
Ducts are a superior look and experience IMO, just slightly less efficient. Nothing wrong with preferring them.
They’re not even less efficient if installed correctly, it just takes some thought and some insulation. And you get really good filtering with very low likelihood of mold in the bargain.
Much like solar panels on the roof (which I have also heard Americans describe as an eyesore), once they are common enough your eyes just slide over them and you don’t notice.
> your eyes just slide over them and you don’t notice.
Nah.
There have been minisplits in the US for years, they are just not very common. Moreover they have been commonplace in Asia for decades now. They are noticeable. I personally think they look like ass. They are huge and you are blind if you don't notice them. There is a reason why ducted or recessed models are available internationally for luxury homes. It has nothing to do with Americans.
Why are they plastic wall-cystst though? Wouldn't a manufacturer offering a less obtrusive look (I'm not thinking of fancy boutique, just Ikea grade surfaces) alongside a standard interface for third party options get a huge market advantage?
Just to add to what the other commentator said, ducted based systems are VERY hard to balance. It is possible using something called an Volume Damper, but it is uncommon (and adjusting them can be challenging, sometimes requiring removal of drywall).
So people COMMONLY wind up with unbalanced floors, and people typically try to fix it by adjusting the vent register opening with mixed success.
Part of the problem is that the thermostat is biased to wherever it is located. You can get systems with remote add-on temperature sensors, but that doesn't by itself adjust where heat/cold is being sent through a ducted system.
The great thing about a Mini-Split is that you're, at minimum, heating each floor independently with its own thermostat. You can then put in e.g. interior door vents that simply let air pass between common areas and the rooms when the doors are closed.
This can go even further with for example two Air Handlers per floor (quad units) on the east and west. So that as the sun moves, the correct level of adjustment can be applied to only the side of the floor that needs it.
I moved from a ducted heating house to a multi head split system house about 18 months ago.
One of the biggest pros (in addition to the improved efficiency of a heat pump) is I heat and cool less space than i did before because i can target individual rooms. When i'm in my office all day I only need to heat my office. When it's hot and I'm struggling to sleep only cool my bedroom. There's no point in heating my living room^^ at 08:30 in the morning if i don't intend to spend time in there till 17:00.
Sure, when it gets to 17:00 my living area might not be comfortable, but that can easily be overcome by turning it on half an hour or so beforehand (either manually or with a timer).
^^ I don't live somewhere where freezing pipes are a concern. But i'd imagine you could just set them differently, slightly above freezing for the rooms you aren't in and a comfortable living temperature in the room you're in.
How would it behave in a place like Chicago where we've had recent weather events that take the temperature from 40F to -10F in a couple of days? Will the system catch up that fast without ducts?
How does it function on a day like today? My evaporative cooler works decently at this temperature but with the side effect of making the floorboards sticky
> owners of drafty homes may need to take on the added cost of insulation when installing a heat pump
Installing good insulation is also really important even if you're not using heat pumps! With bad insulation, you're wasting energy no matter what technology you're using.
I've heard folks who work in the home energy audit business say that upgrading insulation is usually the most cost-effective thing you can do to lower energy bills. Even better, it's multiplicative with other activities like installing heat pumps or solar, so you can install a much lower capacity system and still hit your energy targets.
Most definitely. Here in Scotland, 'Home Energy Scotland' offer grants and interest free loans for various energy efficiency and renewable measures, but for the former you must install roof or cavity wall insulation if its recommended on your energy performance certificate for the building - I'd assume purely because it's the most cost effective measures when applicable.
And in the United States at least, the IRA contains tax incentives for all of that. The audit, the added insulation, the heat pump, and even more efficient appliances.
It’s not always possible. For instance old wood double hung sash windows require a weight box to work. Those boxes can’t really be insulated. And there’s a good chance you don’t want to replace the old windows (or possibly can’t due to historic restrictions) because they are a massive part of the homes character.
Also insulating an old home (pre-WW2) could begin to introduce moisture issues in the walls that weren’t there the last 100+ years since the leakiness of the home would dry the structure. Last thing you want is for condensation and water vapor to build up in the insulation and then begin to rot the wood. Modern build have vapor barriers and airtight seals.
I guess my point is to be careful with old structures without considering things. They were built the way they were because those were the materials we had (old growth wood!) and they were designed to function a certain way.
> For instance old wood double hung sash windows require a weight box to work. Those boxes can’t really be insulated.
In Denmark, this was solved by adding a second, modern window on the inside. The outside kept the same look, and it is even more insulating than a single modern window. Is it a bit clunky to have to open two windows ? Sure. But it is better than not having insulated windows, or ruining the appearance of cities.
On the contrary modern houses often rot because of the water barrier. Condensation gets trapped in the wall and it rots really fast. If you insulate your old house from the inside you wont have this issue. I spent the last 3 years remodelling at 1875 house and we opened all the walls to spray urethane foam. It sealed all the cracks between the wood beams but still leaves the exterior untouched to moisture can leave.
Yeah any house build in the 70’s, 80’s, or early 90’s might had issues with moisture. Water vapor in particular.
Im not sure I’d spend the money (or desire the inconvenience) on a job like that on my old home. I’m not sure I’d make the money back in savings during my time here. But during a gutting, makes sense.
Also, you can use heat pumps with poor insulation just like you can use traditional heating solutions with poor insulation. It's just that you will need a larger system that wastes more energy. Whether that's still worth the trouble in terms of cost of course depends on your current situation of course.
But it's not like heat pumps stop working because of your insulation. They just get more costly to operate. And especially the smaller systems can only deliver so much energy to your house. Basically, if you multiply the maximum output by three, that should be above whatever you are currently using to heat your house during a really cold month. If it's lower, it's not big enough.
If you live in a warm climate, I personally think insulation is the worst (excepting roofing). Not because of efficiency, but because you isolate yourself from nature! The traditional Queenslander (look up Bluey if you don’t know what I mean), has so much going for it. It allows airflow through the whole house, a protected outside to sit and be with nature, lizards coming and going, bliss!
This hermetically sealed environment that we create for ourselves is bad for us.
That can work just fine by intentionally opening windows. Having a "drafty" house is just forcing that 100% of the time (which isn't always wanted).
Side note: As a US resident in an area with a ton of mosquitos, I cannot understand why other countries don't heavily use window screens. Lizards a pretty cool, flies and other flying bugs are just annoying and gross.
> In Europe, outside of the south, mosquitoes are pretty tame.
Use to be... native species were mostly a problem during summer and during night time.
But since about 15 years ago you had a massive spread of invasive Asian Tiger mosquitos (Aedes albopictus) genomic studies show it was likely introduced via Italy and Albania simultaneously.
Those things are nasty, go 24/7, and are just a very different beast in terms of disease vector.
There are already established population pockets as far North as Switzerland. Yet another problem that is likely to worsen as temperatures continue to rise.
Eh, in Romania mosquitoes are pretty bad. And in the last couple of years they're "cousins" came along: tiger mosquitoes. Those cause a really nasty bite
As an immigrant to the US I hate the window screens and have removed the ones I can: it feels like being in prison not being able to truly open the windows. We live in an area without mosquitoes or bugs to speak of, but all the apartments here seem to have the screens anyway.
Insulation can be orthogonal to fresh air. Ventilation energy recovery units [1] exist to help reduce loss from fresh air (and are code for new houses where I am). This has the benefit that you can have more fresh air, for the same heat loss, since the loss will be from the fresh air, rather than through high thermal conductivity through the non-breathable portions of the walls.
Australians have a very strange relationship to insulation and temperature.
Some might say it's the defining feature and purpose of having shelter is that we don't live at the mercy of the weather.
I can't run a business with indoor temps from 24-31c during business hours. Compounding loss of brain function outside of 18-23c is found by every study I've read.
The less exposure to particulate pollution and extreme temperature, the healthier you are, I can't see any arguments otherwise.
Don’t generalise from me. I am a very strange Australian!
From a business perspective, I think you are probably right. I don’t personally find cold affects my brain function (you can put on warm clothing right?), but heat probably does once we get above 30c. It’s summer right now in Aus, might be affecting some of my posting.
For home though, I’m happy for the inside to be much the same as the outside. Mostly though, I just want the interface between my home and the natural world to be permeable. I think that’s good for mental health, and that the pros outweigh the cons. The thing is that you can’t have that and properly insulate it at the same time. So a choice has to be made, and I personally lean towards less insulation/more lizards.
Having said that, we’re all different, whatever floats your boat. If you prefer plastic bubbles inside caves of steel, who am I to judge?
Warm climate, remember? If you cannot cope with an ambient temperature that drops below 20C, there is this thing called “radiant heat”. You can make it with fire.
Also, relatively small amounts of electricity. Radiant, just like your soul would become.
The Queenslander house style was built for large blocks that had sufficient airflow, they were built to be cheap and don't work properly with modern block sizes.
While they are iconic, and have some great design features, the lack of insulation is not one of them.
A modern well insulated house with a heatpump + solar is extremely energy efficient and comfortable in all weather.
“Modern block sizes” will vary where you live, and you can build smaller of course.
Obviously this is location dependent advice. If you live in a lifeless suburban wasteland, then outside is no better than inside. If, on the other hand, there is nature around you, and it doesn’t get too cold in winter, then insulation is a pointless exercise! Get a ceiling fan and learn to tolerate a bit of heat.
I, personally, need nature to stay mentally healthy, and having nature wander inside from time to time helps greatly.
Queenslanders work fine in Queensland, where the lows in winter are still double-digit C. Most of the world (or even Aus) isn't like that. A Queenslander in Canberra would have a massive heating bill 8 months of the year to keep it safely livable.
Yes, true. I kind of lump them together when I think about them, and I think they're often remedied together during retrofits, but they're different issues.
Why can’t my whole home participate in this technology? It would seem an ok fit for things like freezers, refrigerators, hot water heaters, etc.
When it’s freezing cold outside, it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated.
Someone needs to make a standard for moving heat/cool through all appliances in a house…
> it seems crazy that I warm the air of my house and then use electricity to keep the fridge cooler than the air I just heated
The fridge is simply moving a little of the warmth in your room out of its box, and adding a little more warmth to the room in the process. You lose no heat from the room, which is what matters, really. It would be worse to dump the heat outside! At least in winter. The heat has to be removed in summer if you have air conditioning.
In any case, an exterior heat exchanger and heat pump that can handle a wide exterior temperature is much more heavy duty. This could all end up being less efficient, in practice. House-scale heat pumps can efficiently move heat even from a freezing cold outside into a warm interior. Just as fridges can efficiently move heat from their cold interiors to a warm room.
I always joke that in winter all appliances are 100% efficient (I know they're not). Some look at me funny but the ones who pay the gas bill get usually get it.
If you have a resistance electric furnace, that is essentially true. With gas, you add the electric generation and distribution losses, which is a pretty big difference. It does cost more to run an appliance than to heat with gas.
If you account for the electric generation and distribution losses, you should do the same for gas.
"It does cost more to run an appliance than to heat with gas."
That's highly dependent on the appliances involved and the price you pay for each fuel. For me, a heat pump is much cheaper to run. You really need to calculate it for each individual situation.
It's always been funny to me that throughout engineering people chase like 1% efficiency improvements from like 20 to 21 or 35 to 36 and it's usually a big win when achieved... meanwhile resistive heating has an efficiency of 100% and it still manages to absolutely suck.
It only sucks because of generation and transmission losses. If those didn’t exist (not possible), electricity would be much cheaper and they would be on par with or better than natural gas furnaces
How do they affect the air quality indoors? Don't modern (less than fifty years old) gas boilers have balanced flues so that they take in air from the outside and exhaust the combustion products outside too?
Surely properly installed gas boilers always did that even without balanced flues too.
My experience (sample of one) is that they don't. They're supposed to, but VOCs are definitely higher all winter running heat than all summer running air conditioning. Natural gas combustion is at best _mostly_ exhausted.
> My experience (sample of one) is that they don't.
There is something very very wrong with your equipment (or you're measuring something else not having anything to do with the heating equipment - more likely). A high efficiency furnace has a sealed combustion chamber, the entire thing runs in a circuit vented to the outside - combustion air comes from the outside and it is vented to the outside. If it is not airtight sealed from the indoors, it is broken. Even a mid-efficiency furnace with a non-sealed system will vent 100% of the flue gas outside.
> Natural gas combustion is at best _mostly_ exhausted.
Bullshit for any modern equipment (ie installed in the last 50 years).
It could also be that outdoor AQ is worse around you in the winter because everyone is running their boilers, and then that outdoor air ends up inside. I can't test it because I have a heat pump, but I would be curious to know what happens to your VOCs if you turn off your boiler at a time when your neighbors are still running theirs.
Mid-efficiency furnaces are still commonplace in the US, and they don't have sealed combustion systems - they get combustion air from the indoor space, but they vent 100% of combustion products out. High-efficiency furnaces in the US made in the past 30 years or so use sealed combustion with intake and outtake to the outside. (North American high efficiency furnaces older than about 30 years were not necessarily sealed).
But yes, the GP is full of shit. Maybe they have some other non-induced vented gas burning appliance (ie a hot water heater or gas hob), or their measurement equipment is faulty.
Or you live insulated from shitty alliances and low income life.
A friend's husband was killed by a faulty boiler, carbon monoxide poisoning. In 2015 I lived in a house where boiler ignition didn't work and you had to reach inside with a lighter. That unit was definately not sealed.
UK only required consenser boilers since 2005, the ones before that used to air from inside your house.
Condenser boilers and balanced flue are separate concepts. The house I bought in 1978 had balanced flue gas heaters but they were not condensing. Condensing boilers are an efficiency measure. Balanced flue boilers have been available in the UK since the mid sixties.
All I can do is share personal experience of living in rental properties in UK, and if these boilers were really sealed, my acquaintance wouldn't be dead.
Whether most boilers are prehistoric, or it's just years of neglect, I don't know.
But if we're going with the "heatpumps are more than 100% efficient" that everyone brings out, then running my computer to work & heat my room is far above 200% efficiency.
If I'm running my computer to use it & it keeps me warm, there is no way turning on a natural gas heater is going to reduce my costs.
Heatpumps are more than 100% efficient refers to a technical specification measure called efficiency, which is watts of heating per watt of energy input. For space heaters, electric furnaces, and your computer (/many other appliances), it’s always 100%. For modern gas furnaces it can be 90%ish (but the difference in electricity and gas prices mean that gas furnaces are still cheaper). For heat pumps it’s typically between 200% and 540%.
If you have a thermostat in your home, any appliances you use will reduce your heating usage because the thermostat will automatically decrease how much the furnace runs. So, yeah, it’s not wasteful to vent your computer exhaust outside in the winter, but no one’s doing that. On the other hand, it’s not worth it to run appliances you wouldn’t otherwise run unless you have an electric furnace, in which case it doesn’t matter.
Sure but why limit ourselves to "which is watts of heating per watt of energy input." Wouldn't "amount of useful work per watts of energy input" be OK? So if I am putting in 100 watts constantly to my PC I am getting 100 watts of heating & 1 unit of computing. Which is more than 100%
In the summer, my heat pump water heater in the basement is essentially 'free' to run, since most of the heat it captures is by condensing water in the air i.e. dehumidifying my basement. I still need a dehumidifier, but it doesn't have to run as hard.
This is the first year where heating the home with gas isn't an order of magnitude cheaper than with electricity here in the Midwest. Gas still wins, but not by as large of a margin!
I think 100% is pretty accurate for most devices, except for washing machines and other gadgets connected to the sewer. Where else would the energy go?
Your fridge has the potential to go even higher than 100%, as it's a heat pump. But for more than a temporary effect you'd have to keep replacing the stuff inside it with stuff warmed up to outside temperate, which would have to be between fridge temperature and room temperature. Perhaps slightly impractical.
Get buckets of water from your pool (or lake or well) and put them in the fridge till they cool down. Then dump the water outside and get a new bucketful).
To save effort you could run 2 hoses with a small pump.
You are now heating your house with a ground source heat pump.
“100% efficient” doesn’t tell the whole story of the gas bill if you’re heating your house with something cheaper than electric heat (e.g. natural gas).
It's not about fault at all - I'm just saying that the analysis does not apply to lightbulbs. For a lightbulb to be as efficient as a resistance furnace at heating a room, you would need to have zero light escape that room so that all the light would be converted to heat. Then, the heat would leave the room at the same rate as heat generated by a resistance furnace.
Even if we consider incandescent light bulbs, which waste most of the energy they use as "heat", that heat is actually being transferred primarily through radiation, so it can escape through windows more easily than the heat that a furnace transfers to your indoor air.
I assume by “thermal infrared” you mean the IR produced by approximately room temperature objects. Incandescent bulbs produce much higher energy infrared because the filament reaches about 2000 Celsius. Those higher energy waves can go through glass.
Natural gas furnaces are designed to not let that light out. Instead, the light is absorbed by the surfaces of the furnace and turns into heat. The inefficiency in gas furnaces is heat leaving in the exhaust.
The smart thing to do in winter is put municipal liquid water in your freezer, and dump it outside once frozen to thaw in spring. Rince repeat all winter long.
Voila: everyone has heat pump heating! (And dead compressors).
The dumb thing is having the compressor itself indoors in summer. Should be outside.
The issue with that is that if it’s outside, you need a hole in the wall somewhere to connect it.
Today fridges are more or less plug and play. Most kitchens don’t have a hole in the wall going outside where the fridge would go. Some kitchens aren’t even on walls facing the exterior (which I dislike, but they exist)
Interesting, how to remove it easily from the container? Or do you use an ice machine? Is this more efficient than using the heater? Guess it uses heat pump tech.
The fridge isn't the biggest energy hog in the house, but I'm very sympathetic to the absurdity of heat levels in a house.
I often see my HVAC cooling when the set-point temperature is actually _higher_ than the outside temperature. Logically, the house is a heat generator, it makes sense physically. The roof is black, etc.
It would offer a good number of benefits if the system could outright open a duct to the outdoor air, and suck it in whenever the local outside temperature is within the range requested by the user. People who are into optimizing energy use (they exist) can go even further and pre-cool their house during the night in summer.
For this to work, all you need a pusher fan, no refrigeration at all. There might be some pressurization problems, like, you may need a duct both for the intake and outlet. Also might require another filter... but air quality would improve significantly.
This is a really "dumb" idea, but it's perfectly in-line with all the new ideas being thrown out there. The new ideas just tend to throw in an additional heat storage mechanism, like a water tank (in the article). You can get a lot more efficiency gains by saving the night's cold in a tank and using it through the day. But on a more basic level, you can pump straight into the house when the conditions are right.
I've built/retrofitted and a prototype of mechanically operated louvres with push/pull fans for air exchange in an old school building, tied to the thermostat, ac, and a CO2 detector.
The idea of doing the same in my home has been taunting me for years now. Ideally you'd have two such louvres, one with a push fan in the upper floor and the other with a pull fan in the lower floor to simultaneously eject unwanted heat, bring in fresh air, and boost whole-house circulation. They'd be set up to interface with the thermostat/hvac and would operate when the outdoor temperature at intake is lower than the temperature at exhaust and both are above the set point on the ac.
The biggest problem is really one of convenience. You'd need a filter on the intake and a rather large and powerful fan to overcome that static pressure - ergo, a noisy one. And you'd probably have to fully dismantle the system in the winter to prevent the cold from getting in (the Midwest is cursed with both hot and humid summers and cold and dry winters). It just end up being the kind of thing where the devil really is in the details and you either do it right and it's a huge undertaking or you do it fast and sloppy and its drawbacks won't be worth it.
But I agree, nothing is more infuriating than seeing the AC on and the outdoor air temperature being lower than that of the home. And opening windows just doesn't make a difference since in most 20th century homes there's just poor airflow and no circulation.
I was thinking a big vertical heat pipe that sticks out like a chimney would be great for this and keep inside+outside sealed.
When it’s colder outside, liquid will evaporate on the bottom and condense at the top through gravity. Once it’s warmer outside, the whole process just stops.
No valves, no pumps, no analog or digital controls. Ok, maybe a fan.
I actually want a fridge/freezer at the cabin that works like this in fall/winter/spring. I know it’s technically moving heat from inside to outside, but I’ve got more wood than electricity to work with.
I've often wondered if opening windows while AC is running and outside temp is below inside temp is less efficient than keeping them closed.
My thought is I should keep them closed due to extra load on the AC to dehumidify the outside air. Or open windows and turn AC to fan-only mode to prevent stagnant air in rooms without windows.
Unless you have a very strange setup, centralized A/C does not have humidity sensors nor run just to dehumidify. Nor does removing humidity increase the load on the A/C system. Removing humidity is just a happy by-product of how centralized A/C works. So no, you would not be increasing load for that reason.
The above comment is incorrect, even for systems without integrated dehumidifiers. AC systems absolutely do have a higher load with higher humidity because ambient water will condense on the evaporator coils if the dewpoint is higher than the evaporator temperature (which it typically is).
That said, it still may be more efficient to open your windows, depending on the humidity.
I stand corrected. Apparently 60% humidity or so is the line. That said, I live in Florida and haven't ever had an issue, but maybe that's because the A/C runs so much anyway...
FWIW I had a new Lennox heat pump installed a couple years ago, and I can (but don't) configure it to "cool to dehumidify", and it tells me the humidity on the thermostat. I don't know if this is common in new units, or if I'm just special.
Based on some of the home building and HVAC videos I’ve seen on YouTube, it seems pretty common for high-end new home construction in the U.S. (especially the south) to have separate AC and dehumidifier units.
Right. It takes into account both temp and humidity and either can trigger the cooling. It is a two stage system, so usually on the first stage is enough to get the humidity low enough to feel better.
Happy in some times, unhappy in others. There are days I'd love if the A/C would have a humidifier built-in, for those winter months when you might want to use A/C to warm the interior.
A good chunk of the United States (and a number of other countries) uses forced air natural gas heating. If you fall into that group, you can install a "whole-house humidifier" that injects steam into the hot air plenum, distributing it around the house. This makes the air less dry (obviously) but also has the side-effect of actually reducing the need for heating because air holding moisture feels warmer than air without (hence the oppressive heat in the humidity of summer), meaning you can lower the thermostat.
Unfortunately I have only seen commercial humidification units that boil water into steam with the use of natural gas. Without exception, everything for sale for home use uses electricity (you'll need 230V minimum, single phase will do just fine) to boil the water, which is costly (though this year natural gas prices have risen or even doubled, but even in states with cheap electricity it's probably still cheaper to use natural gas).
The moisture can promote mold in the ductwork though. We had our furnace replaced a few years ago and had the central humidifier removed. The interior of the ductwork was black with mold near the humidifier so that was also replaced.
Be careful you’re not running it independently of whether or not the furnace is actually on. 120V generally can’t evaporate enough water in the short window while the furnace is running and many techs will set it up to run at all times (with the blower but not the furnace) to compensate. This lets mildew or mold grow in your ducts.
One of the Daikin models for Japan apartments/condos (known as mansions) has a tankless humidifier; it is able to condensate humidity from outdoor air and introduce it into the home. On a cold winter day it is able to raise the relative humidity from around 30% to about 45% or so. うるるとさらら is the name of their series of things that humidify.
HVAC can do that and it’s not too expensive. You do need to run water to your unit though and there’s quite a bit of maintenance as humidifiers create mold, etc.
Some AC units have two modes - cooling and dehumidifying. When in cooling mode it will blow a lot of air to keep evaporator as hot as possible, so less humidity is condensing on it (but there will still be some). In dehumidifying mode it will blow less air but keep evaporator cool, so more condensation for the same amount of air cooling.
Source - I have Kaisai mini-split at work and I've observed how each mode works (with my hand). There's probably more energy used per cooling amount during dehumidifying, because it's bigger temperature differnce (which means lower COP) PLUS condensing water (water phase change energy is big).
You are exactly describing a HVAC "Economizer" as they are called. I believe they are almost solely used in commercial HVAC installs, probably due to price/additional install complexity? They are very neat though, and do save significant energy in shoulder seasons, or at night in the summer as you mention.
The function to just bring outside air when it makes sense is an extremely common feature in commercial HVAC systems - it’s called ‘night purge’.
Most of these systems have a damper that the system can use to choose how much fresh air is used or how much return air is recirculated so it’s not difficult to use that to just put fresh air in directly with no cooling or heating. Even systems with heat or energy recovery will often have a bypass damper.
You need the humidity to be in the right range as well as the temperature, but it can save a lot of energy!
You'd need one of three solutions to make this work:
1) Long refrigerant pipes. This is unacceptable because it increases the amount of refrigerant in the systems (refereed to as the charge of the refrigerant). Refrigerants are powerful greenhouse gases so it is important to design low charge systems.
2) Another process fluid (e.g. water or glycol). This adds expense (more pumps and heat exchangers). You'd increase the cost of all these systems by a lot.
Also, both 1 and 2 involve running a new set of single use pipes around your house.
3) Make a "single appliance" household. A design like this has been tried - single AC/heat pump hooked to fridge, freezer, oven, dishwasher, washer/dryer, and water heater. The problem is that you really have do design the house around this and it is quite limiting from an architectural perspective.
Combined AC/heat pump and water heater is a thing though.
Adding to (2), I've worked with liquid-liquid heat exchangers (large heat/chiller units for chemical reactors) and they are super quiet and efficient, but boy howdy, are they messy and high maintenance. The glycol lines leak, the water supply leaks, the water needs to be screened and the screen needs to be changed.
Air-sourced exchanger individual appliances are just so much simpler for the consumer.
Not dissing ground-source heat pumps. Those are fine, since they are typically a plumb-once-and-done. You just generally don't want separate appliances which quick-connect.
> Why can’t my whole home participate in this technology? It would seem an ok fit for things like freezers, refrigerators, hot water heaters, etc.
At large scale (think like walk-in coolers of supermarkets), this is actually being done in the form of district cooling [1].
> Someone needs to make a standard for moving heat/cool through all appliances in a house…
The problem is that the piping itself and the circulation required are sources of energy loss, and it's hard enough to keep these appliances sealed so they don't leak their coolant - most coolants have insane CO2 equivalent potentials. It's not worth the effort.
It is technically possible. I had the same thought as you and looked into it some time ago. The only references I ever found to it actually being implemented were in cases of giant walk-in (even warehouse sized) refrigerators/freezers in places where district cooling exists.
For something the size of a home fridge the costs would be immense compared to the energy savings. You're far far better off spending that money on more efficient heat pumps and more/better insulation.
The federal limit for the amount of power a fridge can pull is 527 kWh/year, which at my rates (admittedly on the low end these days) is ~$70/year. There are very commonly available fridges that are < 300 kWh/year, which would be ~< $40/year. So before even taking into account the efficiencies you implicitly make back when you're heating your house anyway, that's your per-attached-appliance limit for input cost on building out, maintaining and running that system.
Though, I admit that the idea of a completely silent fridge & A/C is alluring. Here's to hoping we make some breakthroughs on sold-state heat pumps.
The good news is that the process of running your fridge moves the heat from the fridge into your home, which in the winter is not such a big problem. Your fridge is just another heat pump. It's a bigger problem in the summer when you are maybe trying to cool your house using air-conditioning and your fridge adds heat to your house to keep the fridge cool. Much less desirable.
actually, that makes the room warmer. Your fridge just becomes a bigger heatpump with the door open. the compressor has to work hard to cool a larger area, so therefore uses more electricity and dumps more heat out into the room.
They move the heat from inside the fridge to outside. That heats up your home. This reduces your need to heat your home, temporarily.
Generally, every device in your home that uses electricity is creating roughly the same amount of heat as an electric heater would have using the same amount of electricity. Even fridges and freezers, so long as nothing is being vented outside.
This is one of the bigger myths used to sell tankless. Modern water heater tanks are well insulated; losses are usually quoted as less than 10%.
From a cost perspective, the slight efficiency increase of tankless never pays back over the cost of the unit, and unfortunately, usually the more frequent repairs. The big benefit is the 'unlimited' hot water.
Devices are beginning to appear that can move the waste heat generated by home AC compressor into the pump loop for a swimming pool outside that same home, getting your pool heated for free by cooling your house, and your aircon cooling becoming much more efficient by using your swimming pool as a giant heat sink.
However unless the house was built, and / or the pool installed in a coincidentally fortunate configuration where the AC compressor and the pool filter pump are within a meter or two of each other, these devices cannot be used effectively due to impractical tolerances and insulation needed to mitigate losses from contact with the highly variable outdoor environment.
> nd the pool filter pump are within a meter or two of each other, these devices cannot be used effectively due to impractical tolerances and insulation needed to mitigate losses from contact with the highly variable outdoor environment.
that makes no sense. effective insulation is no problem at all. In large parts of europe they even have centralized water heating and run insulated hotwater pipes to houses across kilometers without huge losses, hell, for this kind of setup it would even be possible to just run refridgerant, which typically specs at ~15m for minisplits as maximum(with very minor losses) distance
Note that this is only an advantage in cooler months, and does work against cooling your home in hotter weather. In principle it seems like we could could build our refrigerators into an outside wall (like iceboxes once were) and then expose the coils in summer, and enclose them in winter.
Not really, efficienty aside the heat it puts out the back is coming from inside the fridge... Which is coming from the room housing the fridge. So over the course of a day it should be neutral.
I think you are looking for (one specific implementation of) Cold district heating.
It can be implemented as a single line of force water flow with 20-25 Celsius. It is viable as both a heat source and a heat sink at the same time.
This thing can be connected to both your coolers and heaters, and thus transfere heat from one to another. Maybe you could even get you desktop computer into the loop.
Usually it implemented on a lager scale, but i don't see why this would work scaled down.
In order to cool your refrigerator, the system has to have a place to the put the "hot" it just extracted. And that place is your house itself; your freezers and refrigerators are warming your house and contribute just like the radiators you installed. So the losses are not as big as you expect them; the money you spend on those appliances also lowers your heating bill.
> the money you spend on those appliances also lowers your heating bill.
It should net out to no less than the same energy though, right? That refrigerator needs energy to move the heat out of the fridge and into the home. If that process takes more energy than just letting the house HVAC deal with it, wouldn’t the energy bill be higher?
Just to be pedantic, but not exactly. The typical design in a domestic heating unit, or refrigerator is mechanical. A fluid is pumped and cyclically compressed/expanded. While electric motors are usually used, they can be driven by any source of mechanical energy; driven directly by a combustion engine is not too unusual.
There are also heat pump cycles that can be driven directly with heat. Refrigerators based on that are relatively common here in Canada in areas without reliable grid electricity. Usually a propane or natural gas flame.
Thermoelectric coolers are actual electric heat pumps; directly moving heat across a semiconductor junction. Not very efficient and quite expensive practically. They're used in those USB drink coolers and to cool down lab equipment. Finding a high-efficiency thermoelectric material that works at normal temperatures and pressures is nearly as much of a Holy Grail as finding a high temperature superconductor.
Strictly speaking you don't need a phase change in the fluid for a viable heat pump; pressure change is enough albeit with worse efficiency. Even something as simple as a Stirling engine with forced circulation of the fluid works as a heat pump.
If you are referring to transcritical CO2 that is absolutely right. However you can't just use any pressure change in any gas, it would work but it would not be economically viable due to that inefficiency.
But they are much less efficient that electrical ones, adding even a small amount of electricity to the cycle (even if the primary energy is heat) can dramatically improve efficiency.
> Finding a high-efficiency thermoelectric material that works at normal temperatures and pressures is nearly as much of a Holy Grail as finding a high temperature superconductor.
No, TECs operates on a quirk related to semiconductor properties and are using electricity to move heat from one side to another but necessarily have resistance. Superconductors however are seeking zero electrical resistance. Current TECs produce 5x heat vs heat moved, and have a limited range of operation and a small range (30c) for the delta in heat between the two sides. I’ve been fascinated by TECs for years and I aspire to freeze CO2 with them, but it’s actually been really difficult to get cryogenic temperatures. You need to build a pyramid that has increasingly powerful TECs drawing heat away faster than it can accumulate. Even then I’m hitting walls in the -30c range because efficiency falls off a wall at both ends as you exceed the optimal ranges for the semiconductor materials.
> There are also heat pump cycles that can be driven directly with heat. Refrigerators based on that are relatively common here in Canada in areas without reliable grid electricity. Usually a propane or natural gas flame.
Notably, the propane fridges used in RVs (which AFAIK usually use ammonia for the refrigerant) are extremely inefficient. They have the huge upside of requiring very little electrical power to operate, but would never be my choice if I wasn't tightly limited on electrical power.
As you said: a Peltier heat pump is a purely electrical device, so if you're using a broader definition of the term, it could be a variety of different types of devices.
But that is the introductory paragraph, the author is defining what they mean by "heat pump": a device for heating a house which is powered by electricity. You could power it with something else, but the point is to replace natural gas furnaces.
My mind parses the term "heat pump" as a device that works on temperature by compressing some medium. Works out just fine for most heat pumps, but not at all for e.g. the Peltier element which is about moving heat from one side to the oher ("pump") but does not involve compression at all.
Hmm, as somebody who knew a bit about heat pumps but not much, I did find it added to clarify/distinguish between the main mode of operation of heat pump, used to accomplish the actual heat transfer; and what power / mechanism is used to move the mechanical bits.
I.e. an internal combustion engine implicitly uses some kind of burning fuel; if on the other hand you want to use electricity as energy source, it needs a different kind of engine entirely. But that, as I understand from the post, is not the case here - heat pump as described here can operate on same principle and look broadly similar in its core parts, whether powered by electricity or something else.
In 2017 we installed a very efficient air-source heat pump and solar panels. My electrical utility offers 1:1 buyback of electricity so I am able to build up a credit in the summer and run the heat pump well into the fall and winter on that surplus. The system is sized for cooling the house which means that it is undersized for heating, but during cool fall and spring temperatures it operates satisfactorily as a heat source.
Our fallback is the pre-existing gas boiler which is much simpler, more reliable and able to be powered by a small generator during our all-too-frequent power outages.
If I am still in this home when the current heat pump fails I will seriously consider a ground-source system instead. The ability to operate during an extended power outage is a significant concern and I expect to always retain the gas boiler as a backup.
I'll also have solar + battery. Should be able to run the furnace & fan but not the heat pump (too many kW/h) during a power outage and thus heating with gas. It'll run off the heat pump for 90-95% of the year, only using gas on the coldest days, or during an outage. To go full heat pump for 100% of the year you need to seriously upsize the heat pump(s) and you wouldn't have performance during an outage.
Why? heated floor are a little more efficient in heating and for some are a little more comfortable, but from my experience they are also slow to react so it's harder to control the temperature when the weather changes daily for example in the spring or automn.
They’re much more efficient (and comfortable imo) than other systems. You’ll see pretty big costs savings. But yes, you need to be in a climate that sees long, cold winters to get the best of them I guess. Or if your home has lots of tile/stone/concrete flooring.
You’re right though, they take awhile to heat up and if you’re in a place where you may need heat at night and AC in the day, they won’t be ideal.
Pretty big costs savings compared to what? if you compare radiators to floor heating, both connected to the same heat pump system than the savings are not significant
It's because of efficiency. The entire floor becomes a radiant source - this is a massive thermal source. A heat-pump is only part of the equation. You need to deliver the heat still. A radiator is generally a bad way to deliver heat from a heat pump. Radiated floors are much better. About 40% more efficient than radiators from the same heat pump.
Not to mention radiators are sort of lousy ways to heat a room anyways. They take up space and leave one side too hot and the other too cold.
It will certainly cost more, especially since you can’t share the venting and blower. But I’d get it quoted to compare. Electric systems have really come down in price per SqFt. Now your climate doesn’t get month after month of freezing temperatures so maybe it won’t be as dramatic but the energy cost savings can be huge. Plus the overall experience of it is the best imo.
You could still circulate air with the blower running in fan mode and you may not need humidifiers as that’s the biggest negative to forced air heat imo.
Curious which humidifier systems you’re looking at?
I got it quoted. Basically would be around $50k CAN for heated floors (it's a big house). Ducted mini split heat pump (2 units to handle the house size) was $60k. Central hybrid gas-heat pump was $30k.
I put in heated electric floors in the bathrooms (about $1k each).
It's not a bad compromise for our climate. Currently living in a home I designed that has mini splits everywhere and I really dont like them. Not enough air circulation and it's really hard to balance given a well insulated house on mildly cool days which is very common here.
I intend to always keep the fan going to circulate the air in order to clean (we have allergies) and humidify.
Until a couple years ago we had a gas-fired tankless water heater which used a single D-cell battery for ignition, which had to be changed once every year or two. It wasn't connected to wall power at all.
There are, or used to be, Bosch tankless water heaters which used a small turbine connected to a piezo-electric igniter, no external power source required ever.
A wood pellet heater can be a fairly complex item, for a backup (depending on what usage frequency backup entails) a wood fired furnace might be more suitable if the owner is happy with having to add fuel every once in a while.
Myself, I would like a ground source system that lets me store in heat from an oil fired AGA, a wood burning furnace and water heater panels on the roof.
Still waiting for one of these people who rave about their heat pump system to actually rely on it full time without a backup. Most folks could barely afford to replace an existing furnace in a place that has all the fixtures installed, much less pay to install a second one based on different setup, and then pay for maintaining two systems on top of everything else. It is absurd to think that this is a plausible way forward for anyone other than the wealthy tech enthusiast. Same thing for induction stoves. You all should start a club or something.
The tech is not ready if you need a backup. I've lived in extreme cold climate areas and no gas furnace I've had has ever needed a backup.
I live in the snowy Great Lakes and I rely on a ground source heat pump and hot water heater full time. No issues at all. Cost similar to a high end gas furnace system when the tax credits were applied. Probably cheaper with air source systems today.
I live in the city and don't lose power, but I'm hoping to eventually use a EV as a battery backup when the equipment is available and standards are finalized.
A battery in a compact like the Chevy Bolt could power my heating system for several days.
It's not like modern gas furnaces don't require power to operate. In a recent Buffalo blizzard power went out and many people with gas heating still froze and had their pipes burst.
Different geographies have different requirements. You're not likely to need to face a week or more of no power after an ice storm in -10'C in Ireland.
There are occassional outages. But the pylons are designed with icing in the mind and that does the difference. More outages are due to poorly trimmed trees falling on wires than ice itself. That usually affects only small area and can be fixed quickly.
> We are living in a developed world with working infrastructure.
You're welcome, we bombed all your infrastructure into oblivion about 80 years ago, now it's all new! And also, your country is quite a lot denser than North America, so you can bury every single power cable (though you don't, obviously) and if you think -10C is cold, just wait until you see what much of North America experiences during the winter.
Define backup? I have a heat pump as my only source of cooling/heat, but it does have a single heat strip in it for the couple days a year it gets too cold for the heat pump alone. There no "second fixture" to maintain.
Same for where I live. And in fact it's arguably a simpler setup since where I live you also need air conditioning in the summer, so many homes already have 90% of what they need for a heat pump setup (which is after all just an AC running in reverse). Installing some other heat source alongside the AC you already have instead of just installing a heat pump for year round needs is arguably the more complicated option.
My heat pump was a retrofit to an existing home with a fully functional gas boiler. Being a ductless split system, it did not interfere with the existing baseboard heat in any way. By retaining the boiler I was able to afford the installation of solar panels and the heat pump in the same year and probably reap 85% of the efficiency benefit for a substantially reduced up-front cost.
Its always funny reading such comments while others are running for years their heat pumps without any problems needing a backup.
Not only they are used in Scandinavia for years. Also in Germany they are used for years. The company Waterkotte operates since the 1980s in Germany and is a pioneer in this showing it is working.
Loads of countries have effective power grids which go down incredibly rarely. I can't even remember the last power cut I had - maybe a few years ago? It's certainly rare enough that I don't need my main source of cooking and heat to take it into account.
My parents live in rural Scotland and use a ground source heat pump for heat and an induction stove for cooking. Power outages happen more often - but still pretty rarely. If they do, they burn wood for heat and eat cold food for a few hours.
And when the grid goes down, then what will you do? How will the utility compensate you for your death when they find you frozen?
This is not an academic question, especially in North America. The weather here can be very harsh.
We lost power earlier this year as the temparature dropped to 0F (-18C). Our contingency (oil heat, oil generator) kicked in and we were fine, but many people were not.
After power was restored, people with air source heat pumps were still stuck, as the heat pumps don't function well at all at those temps, and heating up a house after it has cooled to a low temp is not what a air source heat pump is good at. These are not problems at all for an oil furnace.
If I didn’t have a fireplace I’d probably invest in some kerosene space heaters or similar.
I haven’t had a power outage lasting over an hour for as long as I can remember (years), but that doesn’t mean I’m not considering that scenario. There could be wars or sabotage or whatever. One should always be able to manage for a week or so without power and that will require some form of backup such as a combustion heater of some sort. But having a backup solution that keeps you alive for a week isn’t so expensive. You don’t need two completely separate and redundant heating methods simply because one of them relies on the power grid.
The induction comment was weird. I went from electric to induction a few years ago, and it's not life changing or anything, but it works reliability. I suppose it's faster, but for me the main benefit is it makes it much harder for me to accidentally leave a burner on and burn my house down.
I’ve a 6kW nominal, ground-source heat pump as the only heat source. This is a well insulated building standing atop the soil of a European country with a temperate climate*. It does a great job at +35°C (passively cooling) and just as great at -35°C.
During installation we've even made a mistake and it heated the building up to something like +27°C inside during early winter all without breaking a sweat (or my wallet.)
The tech is ready. Many attempts to apply it is what’s getting botched.
* EDIT: having checked, most of europe falls within temperate – the country is up north.
The article is light on technical details, pointing to a heat pump vendor site for "proof" that they're great.
I live in a heavily populated area with high standard of living, and yet we have had power outages lasting up to a week in the years we've lived here. Almost all in the winter, but also some due to hurricanes. We have have solar, which is great in the summer heat, but not as wonderful in the winter. We have air source heat pump, but also oil furnace backup.
We normally run the heat pump when its above 35F, as the efficiency of the heat pumps drops like a rock below 40F and its just not worth running below 35F. The heat pump is not an ancient POS. It works great 99% of the time, but 1% of 365 is 3.65 days per year. Banking on "most of the time" to be alright all of the time is foolish.
We have diesel generator in case of power outage, which allows us to run the oil furnace using the same fuel as the furnace. This strategy has allowed us to ride through many 1% case scenarios without drama.
Your normal experience is far outside what most people in Europe would prepare for, so our comments on this thread should probably be ignored by North Americans.
Looking at [1], I can see only two power cuts lasting more than 24 hours (Barcelona, 2007 and Cyprus, 2011).
Instead, "major power cut" refers to things like "The power cut occurred at 4:20 pm and power was slowly restored between 5:20 and 6:30 pm." (Glasgow, 2009.)
I can't remember being without power for more than 6 hours, and it's probably more like 3 or 4. I've been responsible for some colocated servers for about 8 years, and there's been one occasion where grid power was lost. That was about 20 minutes. A Raspberry Pi I have in a village in England has lost power once in the last three years.
> I live in a heavily populated area with high standard of living, and yet we have had power outages lasting up to a week in the years we've lived here.
Maybe you are in the USA? The infrastructure situation seems to be different there. We don't have any above-ground power lines in this country (except for high-voltage long-distance transmission trunks) and in the past ten years the power has gone out exactly twice, according to my uptime logs - once for 40 minutes and once for about three hours.
At the risk of asking a dumb question, doesn't working great 99% of the time represent a pretty good solution to most problems by any standard? The tone of the post you're replying to seems to suggest having a backup heat source for rare situations is somehow an indictment of heat pumps, as if addressing your climate control needs 360 days a year without relying on fossil fuels is somehow a failure. Sure, those few days where an alternative is necessary means you might need a backup plan. But that's light years ahead of having to rely on the backup plan every day.
I'd also suggest that the necessity of a backup plan can be reduced as well. Having an unreliable power grid is probably not an immutable law of nature so much as a policy choice and modern heat pump technology performs well at considerably lower temperatures than you describe.
If gas remains expensive in Europe, it won't be absurd, so much as an economic no brainer to have a air to air heat pump, alongside a back up gas boiler. This should happen pretty quickly as renewables take off, and gas is no longer needed for electricity generation when the wind is blowing.
At some point a bit further on, the backup can be simple direct electric heating.
Wouldn't using a lake as a heat/cooling source cause "thermal pollution"? It's probably fine if a couple houses surrounding the lake use it, but if the technology begins mainstream enough to where everyone is using it, it could cause a lot of issues for the flora and fauna of that lake / downstream habitats.
I think in the winter it would be fine to move heat from the lake to houses but in the summer it's worse. We're already having problems with lakes being too hot in the summer which results in evaporation, algae build-up and less oxygen. This also promotes invasive species.
Of course, the question is at what scale we can build such systems and if that would raise water temperatures significantly.
I had a similar idea when I was designing a heating system for a mountain house I was planning on building. I was planning on primarily heating with an oversized wood stove. The excess heat the wood stove would produce would be captured by a heat pump inside the house with its coils in a 500 gallon tank of water that was well insulated. When the house needed heat you could run the heat pump in reverse or make a system that removed the insulation around the tank of water letting the heat out. I had a spreadsheet with the heat calculations. I think the water at 150F degrees had around a megawatt of energy stored in it and that could have heated the house for a couple weeks. I never ended building that house, but would love to build a system like this in the future.
If you have enough sufficiently dry wood, downdraft gasification models burn extremely cleanly (they're effectively rocket stoves), but those models require a fair bit of maintenance, especially if your wood is slightly wet or green, because soot can quickly build up on the water envelope.
I have about 1050 US gallons (4000 l) of water storage in my house. The very effective wooden carburettor heating system is heating up the water storage. Then you use the water storage for next days until you have to re-fire.
That is a standard package provided by many companies from Austria and Germany.
It's astonishing to me to see an article present heat pumps as innovative new tech and insulation as something worth looking into.
In Germany if you want to build a house, almost every construction company will default to some variant of heat pumps. Actual plumbing companies are more likely to recommend an air-sourced heat pump, prefab construction companies seem to have taken a liking to air-air heat pumps (which like air conditioners pump hot air into rooms rather than running hot water pipes through the building for heating) but either way it'll be a heat pump of some kind or another.
Also not only is there a legal minimum requirement for insulation but all grants and subsidies (when available) specify a minimum standard for insulation that must be met. Note that in new constructions they're also combined with a ventilation system to prevent mould and improve air quality. In older buildings retrofitted with modern insulation, tenants are usually instructed on how to vent by opening the windows.
On the other hand, air conditioning is almost unheard of compared to the US outside retail. Even office buildings usually only have desk fans.
I have wondered whether using a small windmill (on the roof) to power the compressor directly could work. This to prevent the energy loss of converting mechanical energy to electrical and electrical to mechanical again. Combining this with a heat/cold storage which is filled there is a lot of wind to be used when there is less, seems to be good idea as well.
The energy those small windmills could generate on a typical house roof is in the double digit kWh territory per year, so I doubt you'd be able to power a compressor with one.
I am in constant bewilderment about all of the talk of saving electricity but still so few homes having a very basic device like heat exchanger.
At its very simplest it is just a box where incoming air is being heated by outgoing air without both getting mixed. It is a bunch of pipes, radiators and two fans in a box.
Whether you heat or cool your house, an open window is energy loss. The heat exchanger lets you keep your house nicely ventilated while reducing those losses due to ventilation by something like 90%.
We had one of these installed in the last couple of years and love it. We wanted to keep our CO2 lower, without leaving windows open and introducing dust/whatnot. Works well quantitatively and qualitatively.
FYI the "industry term" for these is an ERV or Energy Recovery Ventilator. (I think I've seen them referred to as Enthalpy Recovery Ventilator -- but I assume that fell out of favor since it's too pedantic for most people heh.)
If you get one, one tip is to ensure the air inlet is covered with a fine mesh screen. This cut the number in bugs in the filter 95%+. Also you can upgrade the filter from what's included to MERV13 or whatnot for better incoming air filtration.
I live in a large apartment (3 adults, 2 children to 1700 square feet). Recently I bought a good CO2 meter (Aranet4) and I really discovered how much you have to ventilate to keep CO2 levels under 1000ppm.
I sort of knew this for a long time and that's why I, for example, always sleep by an open window. But knowing it is one and actually seeing a completely different thing.
So this caused me to start thinking about installing one or more of these boxes in my apartment.
Logically (and ideally), the incoming air and outgoing air would exchange heat until they are at the same temp, which would be in the middle. So I would not expect an efficiency higher than 50% unless there is some special tech I'm not aware?
Imagine you have two very long tubes joined thermally throughout their entire lengths. For the sake of simplicity, no energy is exchanged with the environment, only between the two fluids.
The cold fluid will meet (thermally, in adjacent pipe) more and more hot other fluid and finally as it reaches the end it will meet the hot fluid at exactly the temperature it comes in. If the fluids are flowing slow enough and the thermal bond is good enough, the cold fluid can get heated up as close to the hot fluid temperature as you want.
And the hot fluid will meet colder and colder other fluid until it reaches the coldest at the other side.
The efficiency of heat exchanger could be as close to 100% as you want, in ideal world.
In real world higher efficiency requires larger device and there is a point of diminishing returns. You also get other losses like mechanical losses due to need to pump fluids through pipes (with large surface area), due to need to have turbulent flow (to ensure mixing within pipes) and due to heat loss to the environment.
Counterflow heat exchangers move the air past each other so that the input air hits the exhaust air in reverse order. The last spot the intake air touches is the first place the exhaust gas touches.
I think another part of this is that there is generally a significant moisture content difference between hot and cool air, leading to some additional gains versus thinking in terms of air temperature alone.
When cold air gets heated up the relative humidity gets lower. If you already have very cold winter which tends to be relatively dry -- you should add humidity and this will necessarily cool the air. While this is not strictly necessary, very dry air is not healthy or comfortable. You typically don't need to add humidity when the temperature outside is around freezing but air is very humid.
And conversely, if you live in very hot and humid climate, you need to remove water from incoming air (actually, there is no other way to cool the air). This unfortunately further warms the incoming air and will necessarily lower efficiency of the exchange. Especially because you don't want to remove only minimum humidity -- you probably want to remove enough of it to get to at least 70% for comfort.
So these are extreme climates. In a more moderate climate you can get away with no need to add or remove humidity and you can get as close to 100% efficiency as you want.
I'd prefer a heat pump that uses ducts I hate the look of ductless heat pump that giant eyesore lump on the wall.
But ducted are not as efficient compared to ductless due to the long runs of ducts and cold attics (even if ducts insulated). Plus my province won't give any rebates for ducted only ductless.
Even better would be ground-source heat pump. But still I'd prefer ducts I think you'd have to with a ground source system.
> Lord Kelvin proposed using heat pump systems for space heating way back in 1852. The first heat pump was designed and built a few years later
That’s the kind of speed we need if this is going to be any help before everything’s on fire anyway.
From what I can tell (in / for the UK at least) heat pumps currently aren’t that great - my dad’s boiler just died and every plumber he spoke to said heat pumps kinda suck and to just get a nice new gas boiler…
"I talked to a bunch of horse tamers and they say cars are just no good. So I bought another horse. I don't see all the hype"
Similar issue in the states. HVAC specialist trash talking mini splits because a mini split's advantage of cheaper maintenance and install is meaningless to the HVAC specialist. Instead they only see the trade offs. Then they quote a bill as if installing a mini split requires a diploma and point out just how uneconomical the farce is.
If the only research you did is secondhand word of mouth, I think you need to do a little more research.
Heat pumps are extremely excellent, and have been for years. We've even reached the point where heat pumps are able to work effectively in places like North Dakota. For reference, the UK doesn't even have the concept of weather like that.
Sorry, but I don't see any novelty here. Everything described in the article is commercially available. At least here in Germany.
Heat pumps are used to heat a storage container called buffer, a water container of 200l or more of water. This is used to run the heat pump when energy is cheap to warm up the buffer. That is for example in daytime when energy is available from the photovoltaic. If you don't have photovoltaic you can also have a good energy price when running this at night.
Also the storage of the heat in summer is nothing new. These systems are also commercially available for years. It is only that they are so expansive that many companies have backed out of those.
The idea here is that in summer time you heat up a big tank in the ground like with a thermal system on your roof. Then in winter time you use that "saved" energy to run the heat pump. At the end of the winter the water in the tank will likely be freezing. That state change of the water will give an additional energy boost, because it is the same amount of energy you need to boil water. All this is well known and working and commercially available for years.
The novelty claimed is directing excess remaining heat in the refrigerant on the normal heating cycle, after it has passed through the heating coils in the house, to the buffer tank. Not the idea of the buffer tank itself.
Seems you're describing something a bit different? In this case, this energy is used to run a cycle defrost on the evaporator rather than run the heat pump.
This is like when Apple introduces some new feature that existed on Android for years and claims it as some sort of revolutionary thing. In this case it's just that the mainstream US has discovered heat pumps when they have been mainstream in Europe for many years.
Millions of people have used them for years. They just weren’t as popular due to gas being cheaper and available everywhere. There’s been a bigger push the last 10 years as gas prices have gone up. So they’ve been there but it didn’t make sense to use. You have to remember that things like gas are much cheaper in the USA. There’s just more natural resources here.
My dryer is a heat pump. The only issue is it takes a long time to dry my clothes, but the benefits are huge power use decrease, and so much more gentle on my clothes.
Interesting! Do I understand correctly that the additional water storage just cycles between 0°C and below room temperature to further cool/preheat the coolant? Hard to believe it could have such a big effect.
And how does it fit into existing setup? I can imagine it can be connected before water boiler to supply the lukewarm water.
For our house, a ground loop heat pump would be best. A long slit trench, with the slinky style of coolant loop, in the back yard (away from utilities) could easily handle all our waste heat in the summer and source heat in the winter.
Wouldn't it be cheaper/easier to dig a well, fill it with tubing, and pouring concrete all over? The concrete being the constant-ish temperature heat reservoir ?
My parents built a new home a couple years ago. The property had a well despite being on city water. They have other homes with ground source heat pumps. When asking the geothermal contractor if they could use the same well borehole, the contractor said why don’t we just circulate the water and not bother the existing well. So that’s what they do - their geothermal system uses the well water, circulates it through the condenser, then sends the water back down into the ground.
This is fascinating! Is it possible to do this while utilizing the well for drinking water? I would assume so - it would just go through the condenser to exchange heat before being used elsewhere, and less would be pumped back down to the well?
People in the UK are talking about the risk of heat pump installations being in the tens of thousands & not possible everywhere. This is mostly from anti-green MPs. Anyone know what the facts are there?
I don't know where the heck all this extra electricity for heat pumps and electric car charging is going to come from. In CA if you get a slightly hotter than average summer their electrical grid goes into chaos. Get a slightly colder than normal winter and the north east and central grid freaks out. I'm all for transitioning to renewable energy (nuclear makes the most sense if you take emotion and bullshit out of it) but we have a long way to go before we can just ditch gasoline, diesel and natural gas any time soon. Heck how many millions of US homes will have to get their electrical service upgraded, never mind the base electric infrastructure?
A heat pump operates at 2x to 4x the power efficiency as compared to resistive heating. Many places are unfortunately only doing resistive heating because of cheap install cost. If we can replace that with a heat pump that's a big win for everyone.
"Stuck at home during the first UK lockdown of the Covid-19 pandemic, the thermal engineer suddenly had all the time he needed to refine the efficiency of heat pumps"
I've seen that story a few times now. The free time let a lot of innovation happen. Fuck jobs
In Vermont, we are in our first year with heat pumps. Have a wood stove as backup and supplement when we want to go pantsless mode. The original oil burner is currently turned off, out of commission waiting on some parts. We could go without the wood stove, and have done so for stretches.
We installed Mistubishi Hyperheats, 3 external units, 5 heads. Zero interest financing by installer, for about 21k all in including electrical work. Earlier this year we also did air source hot water heater, for about 4k all in.
We were spoiled by the whole house air conditioning over the summer, and the heating has been performing just fine. It about doubled our electric consumption, but that bill is still less than my oil bill was, before the price of oil nearly doubled.
We're motivated primarily by a desire to minimize fossil fuel consumption, and then to mitigate volatility in fossil fuel markets. With this install we completed electrifying all utilities in the house , and have a rooftop solar array that previously offset the entirety of our consumption, but will not at current levels.
The heat pumps will just about pay for the cost difference between them and a new oil burner before their parts warranty is up. Add in the cooling, and the increased control and comfort we have, and it's a pretty sound investment, IMO.
As an anecdote, the conversation at the local bar in Rutland, VT the other night was all about people planning to get heat pumps, or promoting them after having them installed. Not wealthy tech enthusiasts, but bartenders, small business owners, and working class families. With the IRA inventives, and the price of heating oil -- it's becoming a normal thing, not an exception.
I'm curious about the disposition of the local HVAC companies and tradespeople there. Do you feel confident that you could get emergency service in cold weather? I like this technology a lot, but I live in an area where I can't get most companies to take my request for a quote seriously if it's not a standard central air, furnace or water heater. I had to DIY my Rheem heat pump water heater in 2021 because I couldn't get a quote from a plumber.
It depends on what you mean by "cold weather", but modern air source heat pumps are getting increasingly efficient in surprisingly cold temperatures. This Samsung model I randomly found from a Consumer Reports link (https://ashp.neep.org/#!/product/65014/7/25000///0) claims to still heat almost as effectively well below freezing as it does at more mild winter temperatures.
Even for less effective heat pumps, gas backup isn't really a requirement since you can often use electric "heat strip" backup like my home does. Heat strips are not particularly energy efficient, but many places that can get cold during the winter aren't continuously cold, so a less efficient electric backup is just fine.
for those places where the scop is low, you have to drill for heat.
If that's not possible then maybe a system where you can burn wood to suck the heat out of that.
If you live in Alberta, they still don't exist because you need it to handle -40C or even -50C in winter. The vast majority of Canadians live within 100 km of the US border and don't see temps that low though.
Everyone is looking for an easy answer to climate change / energy costs / energy independence etc. But there isn't one. Fusion remains decades away, Fission is very expensive and unpopular, Most renewables are intermittent etc. Heat pumps are one more tech with very limited potential (range of temperatures, efficiency over that range, power output limits, need for a heat source, size, cost etc).
Wait, you are telling a bunch of technologists that no technology is perfect? Stop the presses! Which, dang it, are clearly also an imperfect technology if we have to stop them every time there's fresh news.
What's your perspective on sustainable biomass usage such as pollarding and coppicing, and bringing energy usage inline with that which can be fueled by them, in addition to small scale wind?
Half way through the article the author is touting how these can work in cold climates like Norway, then their example homeowner immediately states they have this but also they still have a furnace for when it actually is cold. Why do journalists try to pull crap like this? Contradictory information in the same paragraph!?
If you have to have a backup it is _not_ a replacement and it will not get us off of carbon. Most people cannot afford a heat pump system much less a heat pump _and_ a furnace. Heat pumps seem great for moderate climates but it is not gonna happen up north where things actually get cold and stay cold for long periods of time.
Anyone who actually has experienced this type of cold would run in the opposite direction of a heating technology that produces less warmth the colder it gets outside. Literally the opposite of what is needed for existence.
If you read the article carefully, it notes that part of the problem in some colder climates is a lack of home insulation. Norwegian homes are well-insulated and therefore very suitable for heat pumps. The home owner with the furnace was US-based, by the way.
The author is not "pulling crap" because they point out the real experience of Norwegian home owners while also describing the diversity of heat pump installations and outcomes.
A solution doesn't have to move us away from fossil fuels all by itself to be a useful piece of the puzzle. Even if heat pumps were only viable in places that don't regularly get super cold in the winter (which isn't true), that's a huge number of places covering a large portion of the population. A lot of the US, for example, gets hot enough in the summer that you want central air conditioning but also gets moderately cold in the winter. A heat pump system can cover you all year round with the same exact system. If you install a backup heat source, which can be electric by the way, that covers even more potential installation locations.
It's not that black or white. I only need a backup for my heat pumps for perhaps a week each winter. The heat pump still saves me 40% on my heating costs throughout the year.
Also, Norway doesn't get as cold as you might think. They get some heat from the gulf stream in the Atlantic ocean like the UK does. Russia and Canada get a lot colder in their northern parts, like -40C quite often and sometimes even as low as -50C. Heat pumps aren't very viable below -25C, but work is ongoing to make the more efficient at lower temps.
I’ve been wondering where the break-even points will be for ground source systems, too. I was talking with an architect a couple weeks ago who has looked into that for several projects and didn’t find the number close to working out, but that was in Boston where the winter climate is nowhere near that extreme and the labor/land costs are very high and space issues meant they’d have to do the most expensive vertical boreholes.
10 years ago the average heat pump had a CoP of 3. Today they are 4 or a bit higher. Some ground source heat pumps have a CoP over 5. I saw one unit with 5.3. Of course, with a ground source heat pump, you can actually get that CoP when the outside air is -50C.
Ducts are dead.
The Daikin Alira X is the gold-plated option and cost $8k AUD for 2x2.5kw and 1x7.1kw units including installation. Payback time is about 3 years. The system is oversized, but enables excellent zoning and of course provides cooling which is a must on 40C/104F days.
Why do they seem to be so much more expensive in the US?