A combined hydronic air handler is a forced air heater which uses hot water as its heat source. A hot water line is run to the unit which goes through a copper heat exchanger (radiator) which dissipates the heat to the air that flows through it. The hot water is then returned to the water heater via another pipe. These units can run off of most domestic hot water heaters. If used with a tank hot water heater that also supplies the domestic hot water, you gain efficiency from that hot water heater because its heat loss remains the same but it is serving more demands. Combined hydronic air handlers are very efficient (as efficient as your hot water heater) and are very flexible. They can deliver a wide range of heating loads and be adjusted accordingly. They also deliver air that isn’t too hot and can be properly mixed in your home to deliver greater comfort and efficiency. These units also support Air Conditioning to the home by installing a cooling coil and an outdoor A/C
Radiant heat is primarily heat delivered into the floors, which heat up, and radiate up evenly into the room. There are two different types of radiant heat sources – Electric and Hydronic. Electric radiant heat is expensive to run because of the cost of electricity and is not normally advised if other, more efficient, options are available. Hot water piping is usually run through a concrete slab floor, grooved plywood subfloor or tile floors. When heat is called for, hot water is pumped through the pipes and the heat is transferred to the floor and then to the room. The water running through the floor is then returned to the hot water heater. The hot water source can come off of most domestic hot water heaters. Just like combined hydronic air handlers, utilizing the same tank water heater for domestic hot water and radiant you build up the efficiency of your unit. Hydronic radiant heat is very efficient and delivers even and comfortable heat throughout the rooms it supplies heat to.
A heat pump is essentially an air conditioner system running in reverse. An air conditioner removes heat from inside the home and transfers it outdoors to cool your home and a heat pump removes heat from outdoors and delivers it indoors to heat your home. They deliver the heat to the rooms in your home using the same air ducts as your air conditioner or mini split system. Refrigerant is what makes the process possible and very efficient.
Heat pumps are a very efficient and comfortable heat source. They deliver air that isn’t too hot which allows for proper air mixing giving you the same temperature throughout the home (as long as your air flow is balanced). Heat pumps can also be sized to the low loads that we have in California. They can be up to 350% efficient using electricity and refrigerant.
A gas furnace is an air handler with a heat exchanger that is heated by burning natural or propane gas. The air handler fan blows air passed the heat exchanger, which is hot, which transfers the heat to the air. Then the air is delivered to the rooms via a forced air duct system. Except for the higher end very efficient furnaces it is difficult to match them to the low loads we have in a California home with moderate performance measures applied to it. Also, there isn’t much adjusting possible to a normal furnace.
Passive solar is an elegant and unique way to heat your home. In the cold months, sunlight shines through south facing glass and delivered to a thermal mass. A good thermal mass holds the captured heat and releases it slowly and evenly until it is heated again. If a home’s primary heat source is going to be passive then there needs to be great attention given to air sealing, insulation and ventilation.