Yes, air-exchange heat pumps have been around forever. But they're usually of the all-the-way-on or all-the-way-off type in the US. Newer systems use variable refrigerant flow and variable fan speeds to save energy, so they run more proportionally to the heating/cooling load. They have a higher up front cost so production builders don't put them in, but custom home builders will.
In cold climates you eventually hit an efficiency wall with the air-exchange units and need to use a ground-source heat pump, with glycol pipes being run deep in the ground to exchange heat. And/or also have a supplemental source of heat that only comes on during the very coldest periods (oil-fired furnace, natural gas, cast-iron stove, or even resistance heat).
In hot climates you can increase the efficiency of a heat pump by adding water mist, making it a hybrid swamp cooler. Evaporating water will take out a bunch of heat energy.
As was mentioned, insulation is key otherwise you're just spending money on heating or cooling the outdoors. Walls, door, and windows that don't have thermal bridges, controlled air exchange with the outdoors (ERV energy recovery ventilator units), and so on.
In cold climates you eventually hit an efficiency wall with the air-exchange units and need to use a ground-source heat pump, with glycol pipes being run deep in the ground to exchange heat. And/or also have a supplemental source of heat that only comes on during the very coldest periods (oil-fired furnace, natural gas, cast-iron stove, or even resistance heat).
In hot climates you can increase the efficiency of a heat pump by adding water mist, making it a hybrid swamp cooler. Evaporating water will take out a bunch of heat energy.
As was mentioned, insulation is key otherwise you're just spending money on heating or cooling the outdoors. Walls, door, and windows that don't have thermal bridges, controlled air exchange with the outdoors (ERV energy recovery ventilator units), and so on.