This is why the building code in high risk areas should require Class A fire resistant roofs. This won't protect homes from huge firestorms but they're effective against falling embers.
When Paradise was burning I was thinking if I lived in a fire prone envionment; I would have sprinklers on roof of my home. It would be a simple 1/2" copper pipe feeding a few sprinkler heads on the roof. Maybe a few mercury switches placed around the property, or remotely controlled through the phone line, wifi, or sat phone enabled? Nothing too elaborate. It wouldn't protect everyone. It might save a few house fires that were started with embers though?
I know there one company selling roof fire sprinklers. I know of one small city who's experimenting right now with roof sprinklers. Hell, I wouldn't mind firing a bunch of Firefighters, and seeing that money go to Roof Sprinklers. (I haven't quite figured out exactly what Firefights do all day, with the hard exception of Paramedics. Buildings in cities don't burn like they used too. Wood stick homes in the country are another story.)
I heard one guy say that there wouldn't be enough water pressure if everyones roof was on, but that doesn't make sence either. Not everyone's roof sprinklers would be going off simultaneously if properly implemented, and designed. Firehouses could be in charge of which houses sprinklers go off?
Right now in CA, if you live in a fire prone area, Insurance (Property) is not suspose to be higher. As much as I despise Insurance companies--this provision needs to be nixed. (I don't think it will happen because Insurance companies use it to raise our city insurance rates, and politicians have northern cabins.
A small residential fire sprinkler head outputs around 15gpm of water. While keeping a roof wet is different than wetting down a room on fire, a roof is big and you need to be sure it stays wet, so let's say you want to keep it wet with 30gpm.
And lets say you have to keep it wet for 24 hours until the fire danger passes. That's around 40,000 gallons of water.
Where are you going to get that water? You can't count on the local utility keeping pumps running. If you're lucky you have a well, but a good residential well would yield around 10gpm, and if you and your neighbors are all pulling out water at the max rate together for hours or days, it may run dry while you wait for water to percolate in.
So you need a huge tank of water - a 50,000 gallon tank is around 35 feet in diameter and 7 feet high. Hope you have a big yard and lots of money, the tank alone will probably cost $30K. So figure around $50K to install the system. I hope you have a big back yard for it.
That bunch of firefighters you want to get rid of help protect many square miles of land, putting that $50K sprinkler system on 10,000 homes would cost $500M - that's a lot of firefighters and equipment.
I think there are better ways to keep your roof from burning, but even a metal roof is no guarantee that your house will survive a large wildfire unless you also keep the land devoid of fuel. And you could still fall victim to a piece of flying ember that happens to land on a vulnerable spot of your house.
Don't forget that most of the water you sprinkle onto the roof will collect in the gutters which can feed immediately back into the tank, so you only need enough water for a few cycles plus 24 hours of evaporation loss - still a decent amount of water, but a lot more like a large garden water-butt than an industrial tank.
That sounds like moderately more flow than needed for much longer than needed. Based on some searches for bushfire tanks, you could meet the water storage recommendations for $3k.
And sure, the idea of replacing the fire department is probably not great, but it wouldn't hurt to have a bunch of these around.
I think getting rid of firefighters and installing hoses on your roof is probably not the idea of the century. Do you suppose its the asphalt catching on fire?
Houses burn (usually) because they have vented attics that embers can blow into. Fire screening your attic or not using vented attics altogether, along with concrete and masonry construction and reasonable vegetation management go a long way toward protecting structures but the fact that structures are there in the first place is the problem.
You can't take an ecosystem based on periodic fire cycles and turn it into a suburb and expect everything to continue to work. Forests need to burn a little bit all the time or they will burn a lot all at once.
While these are earnest and constructive suggestions that would work in some contexts, I'm not sure you're taking the drought conditions into account. The basic problem we have in California is that water levels are hitting historic lows while forests are bone dry and so are the winds that fan fires.
While sprinklers are probably impractical as they require large storage or that you (and your neighbors) starve the mains, I'll bet that a person could design a fast-to-deploy thermal blanket system of some sort.
