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SPACE HEATING : Direct Hot Air Heating, Heat Pump Preheat, Air Radiant Floor Heating
WATER HEATING: Water Preheat
EQUIPMENT HEATING: Clothes Dryer Air Preheat, Heat Pump Heating
COMMERCIAL: Industrial, Commercial, Agricultural
How to Use Your Heater Boards for Air Radiant Floor Heating
People who have radiant floor heat, know how comfortable it can be. The reasons are simple; the floor stays warmer, the floor temperature stays more stable, and the temperature from the floor to the ceiling stays more even, humidity level can stay higher, and air movement in the room is lower, than with other direct air heating systems.
Without radiant floor heating, the floor temperature drops to low 60s and can be colder if it is over an un-insulated crawlspace. The chart below shows one example of actual crawlspace temperatures in a modular building in North Carolina during three winter days. During those days, the skies were clear and sunny. A Heater Board system would have produced solar heated air at about 40 degrees warmer than the outside air and filled the crawlspace with warm air. The chart shows the estimated temperature at the top of the crawlspace, just under the floor, with the Heater Board system flooding the crawlspace with warm air.
Usually, a radiant floor heating system requires a boiler and miles of continuous plastic tubing buried in concrete poured on top of the floors or, tubing wound tightly against the bottom of a plywood subfloor, wrapped in shaped aluminum plates and stapled against the plywood. Hot water is pumped through the water tubing to heat the sub floor below the finished flooring. The maximum temperature of the finished flooring only needs to be 80 degrees F to have a big influence on comfort.
However, there is a much simpler way to achieve the benefits of a radiant floor and that is with air as the radiant heating fluid. Heater Boards have been used this way to heat crawlspaces below first floor rooms to deliver Air-Radiant Floor heating. No complicated plumbing is required because the warm air does all the work of transferring heat to the floor.
To use this method in a crawlspace, all you need to do is connect the solar air duct from the Heater Boards, to a crawl space vent or to an unfinished basement. The warm air from the Heater Boards will rise up to below the first floor and heat the plywood sub floor. Since heat rises, the heated air will move up into the crawlspace and hug the plywood sub floor overhead. Once the plywood floor is heated, the heat in the sub floor will rise through the plywood to heat the finished floor inside the house. No air moves through the floor. It is simply heat moving from the warmer air below, through the wood, to the colder interior finished floor. The large mass of the of plywood and floor joists in the sub floor, (approx. 5,000 pounds per 1,000 sq.ft.) will act to retain heat and release it gradually to the finished floor above. That gradual release of heat will carry the heating effect into the evening hours.
Heater Board Air-Radiant Floor Heat download
In many cases, there is no need to run ducts through the crawlspace since the heated air will always spread out and rise to cover the sub floor. However, if you have a large crawl space, you may want to install several separate Heater Board systems to quickly distribute the heated air to widely separated parts of the space.
If you have insulation below the sub floor, and you have convenient access to the crawlspace, you may want to open a few areas of the insulation to allow the solar heated air to move up past the insulation to contact the sub floor. If this is impractical, you can still benefit from the solar heated air moving against the bottom of the insulation. In such a case, the insulation and floor joists will become warmer and the heat will move slowly up through the insulation to the sub floor.
To attach the solar duct to the crawl space vent you can use a duct outlet available from the online store. The duct vent can be attached by wiring the outlet to the crawlspace vent then attaching the solar duct to the outlet. See the photos. In this case the fan would be installed outdoors between the Heater Boards and the crawlspace vent.
You may wish to bring the solar duct directly in to the crawlspace, where you can attach the fan and power supply inside, in a dry location. If you can remove the crawlspace vent screen, you can bring the solar duct into the crawlspace. If you have a wooden of sheet metal crawlspace walls, common in manufactured or mobile homes, you can cut a hole in the walls to bring the solar duct inside. In older homes with stone walls around the crawlspace, you may be able to remove enough stones to create an opening.
If you have water pipes in the crawlspace, the solar heated air can help keep them from freezing in cold weather. However, you should ensure that the power to the solar fan is controlled by a thermostat that will prevent it from operating when the solar air supply temperature drops below about 40 degrees F. This is to prevent the fan from operating at night when it can bring cold air into the crawlspace. It is best to operate the system off a differential temperature controller that will turn the fan on whenever the Heater Board temperature is warmer than the crawlspace temperature.  
If you live in a cold climate where freezing is likely, you should consider a backup pipe heating system, such as heat tapes, for extended cold or cloudy days or nights when solar heating is not available when solar. If you heat tapes are thermostatically controlled, the additional solar heating will reduce the electrical energy use of the heat tapes.
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