- Heating Systems:
- Boilers add heat but allow air to circulate freely, while furnaces add heat and mechanically move air within the building.
- Some boilers and furnaces also draw combustion air from the building. Water heaters usually draw combustion air from the building.
- Ventilation:
- Exhaust fans move local air and moisture out of the building;
- HRVs do the same while transferring heat to incoming air.
- ERVs bring in fresh air with little change in temperature or humidity.
- Air Conditioning:
- Cools and dries air while circulating it within the house.
- Residential system usually do not exchange air with the outside