How It Works

A "combination system" heats both the home and the hot water for domestic use. The schematic below shows the system providing both space heating and water heating at the same time.

A solar water heating system automatically feeds the "cold water" line entering the system (see top left of schematic above) whenever a hot water faucet is opened. A portion of this energy helps solar-heat the floor, while the rest helps pre-heat the water heater, reducing energy used for water heating. In summer, the bypass valve (top center) is turned and solar hot water continues to pre-heat the water heater.

Note: this same design can be used without solar pre-heating - in that case, the bypass valve is only be used when the system requires repair, and the incoming cold water provides a slight cooling benefit to the floors (the cold water flows through the floor before entering the water heater, slightly cooling the floor and slightly pre-heating the cold water entering the water heater).

The Radiant Heat Distribution System

There are two types of floors in the home - slab on grade as well as a raised wood floor. The radiant tubing is placed under both floors as shown in the details below.

HUGE Cost Savings

A system design such as this, and this is but one (albiet simple) example of many possible configurations, saves cost in both installation and operation.

The installed cost of a system such as this is comparable to, generally less than, most other space heating system options. It depends on whether it is new or existing construction, access room in the crawl space, local cost of materials and other factors.

The operation cost is significantly less than most other space heating system options. For example, a central furnace uses a 600 to 700 watt blower to distribute the heat through ducts in the home while the radiant system uses an 80 to 120 watt pump. A central (ducted) furnace generally has a lower distribution efficiency than a radiant system (65-75% with ducts versus 85-95% for hydronic tubing). For example, a typical (existing) central propane-fired furnace may cost $32.90 versus $18.91 for hydronic (per million Btu heat delivered). Click here for a comparison of costs in Nevada County, California.

Superior Comfort

A radiant heating system provides greater comfort than a central furnace because it provides warm surfaces in a cold space. Much like a woodstove can "bake your body" if you stand close to it in an otherwise cold room, a radiant system uses the same principle. The radiant floor is simply a larger area at a lower temperature than a wood stove, but it accomplishes the same effect. Homes with radiant heat are often set to heat the home to just 65-68F, whereas the thermostat in a central furnace system is generally set above 72F to achieve comfort. Also, central furnaces create air movement, the flow of which can create a slight cooling effect (not to mention move dust around!). In summary, a radiant heating system provides a superior heat source for comfort, and at a lower air temperature.