Create Solar Heat for Metal Buildings Using TAP

The low-cost way to add solar heat to metal buildings, including how to build using the TAP system, cost of materials, and diagrams for ducts, dampers and framing.

| July/August 1986

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    The integrated thermosiphoning air panel (TAP) is the perfect solar collector for metal buildings because the side of the structure can act as the unit's absorber plate.
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    Grilles inside the building?at the top and bottom of the collector?allow room air to circulate through the solar heater and be warmed. Each duct opening should ideally be about twice as large as a horizontal cross section through the solar collector itself.
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    Diagrams of the collector frame, backdraft damper and duct, and damper and duct patterns.
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    Costs to build the integrated thermosiphoning air panel (TAP).

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 Reprinted from MOTHER EARTH NEWS NO. 91. 

The easy, low-cost way to add solar heat to you mobile home or metal outbuilding. 

Create Solar Heat for Metal Buildings Using TAP

The integrated thermosiphon air panel (TAP for short) is a fresh approach to solar air heating—one that's perfectly suited to the 10 million or so folks who live in mobile homes and to owners of the countless metal-sided storage, industrial, and commercial buildings around the world. By making use of the building itself as a part of the collector, the TAP keeps material costs down, simplifies construction, and maintains a low visual profile. And because it relies on thermosiphoning to move air past the absorber, the TAP avoids the complexity and cost of an electrically driven fan.

What It Takes

What do you need to build your own TAP? The critical element, of course, is sunlight for solar heat: You need a metal-sided wall that faces within 25 degrees of south and that isn't shaded in the crucial winter months. You'll also need some hand tools, such as a drill, metal snips, screwdrivers, a caulking gun, a 1/4 inch nut driver, and maybe a circular saw. Add to these items less than $100 worth of locally available materials and a weekend's work, and you'll have solar heat flowing into your home.

How Big?

A rule of thumb for solar air heaters is to allow one square foot of collector for every 10 square feet of floor area you wish to heat. (The room should first be caulked, weatherstripped, and at least moderately insulated. Always take care of such energy-conserving fundamentals before adding solar heat.) Thus, a 180-square-foot room suggests an 18-square-foot collector. This, however, is only a rough estimate. The available wall space for mounting the collector and the limitation of standard tempered glass sizes (28 inches, 34 inches, or 46 inches by 76 inches; 34 inches or 46 inches by 90 inches ) will determine the actual dimensions of your collector.

Because the TAP relies on passive airflow to distribute the heat collected on its absorber, you'll get the best results by sizing the collector to warm the room directly adjacent to the wall on which it's mounted. Though heat will eventually be transferred to other rooms, oversizing the TAP to try to heat more than one room will make the first room too warm.


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