Hydronic Heating Systems
Hot water (hydronic) heating systems usually consists of a boiler and a heat distribution system. This distribution system shows baseboard radiators. A wide variety of radiator types are available. Hot water is supplied directly to the radiators and returns to the boiler by way of a separate line. An expansion tank provides a cushion of air for heated water to expand into if pressure builds up in the system. An insulated fresh air duct provides combustion air directly to the boiler.
Because hydronic systems have no air movement an air to air heat exchanger is used to maintain indoor air quality and transfer heat from the exhaust air to the incoming fresh air supply. Fresh air is supplied (individual ducts) to each room while exhaust air is removed from the kitchen, bathrooms, hallways and laundry rooms. Two separate ducts (intake and exhaust) are installed through the floor header area and must be at least 12 feet (4 m) apart to prevent cross-contamination.
Radiant Floor Heating Systems
Radiant floor hot water heating systems work well in an energy efficient home. Hot water is distributed through water pipes installed in the floor. The layout and distribution of pipes is determined by the building heating requirements. Insulation is necessary under basement floors to help reduce heat loss to the surrounding earth. A reflective material and Insulation are recommended for all floors to maintain heat transfer in the desired direction (usually upward).
With this type of heating system, a balanced mechanical ventilation system which exhausts stale air and supplies fresh air separately (preferably to every room) is essential to maintain indoor air quality. Air to air heat exchangers (also called 'Heat Recovery Ventilators') are recommended for energy efficient homes.