It's really interesting how the task of heating a home (and providing hot water) is solved so radically differently in different parts of the world. Some areas seem to use only wall-mounted air-air pumps, and gas burning boilers for hot water, some times even without hot water storage i.e. direct burning (Something I have never seen in North Europe). I use a combined heat pump with hot water heater/tank. The whole thing is about the size of a regular closet and the heat pump has no outside unit. It uses only the heat in the return air leaving the house. So basically it handles ventilation, and cools the air being vented out, re-using it for heat. These cost $5-10k and last 15-20years. This to me is a pretty reasonable cost given they do all ventilation, space heating and hot water production in one. And there are no pressurized lines anywhere because it's a single self-contained unit without an outside part.