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Solar Heating

Solar Heating


Tom Snyder

©1994 Tom Snyder The principles of solar heat have

been known for thousands of

years. A black surface gets hot in the sun, while a lighter colored surface remains cooler, with white being the coolest. Enclose black metal in an insulated box with a transparent cover and voila, a solar collector.

Taking a shower with solar-heated water, or heating a house with solar-heated air or water, (or drying corn in the Midwest) is a natural and simple method for both conserving energy and saving our fossil fuels. When a solar heating system has been designed and installed correctly, it can be aesthetically appealing and also add to the value of your home.

The value of any improvement to a home can be both subjective and objective. With solar heating, the panels can be, subjectively, a real eyesore. On new construction, they can be worked into the building design to be almost invisible, while on existing construction it can be a real challenge to make them fit in.

The Four Parts of a Solar Collector

A solar collector consists of the exterior framework, insulation, glazing, and collector plate.


Many choices for the framework of solar collectors are reasonably available. Wood, plastic, steel or aluminum have all been used with varying degrees of success, but nothing is as good as aluminum. Aluminum weathers the elements with very low maintenance, and has color choices baked on, so there is no need to paint the exterior of your solar panel.

In the spring of 1972, I tried to build a 4 foot by 8 foot solar panel out of standard dimensional lumber, i.e., 2x4s, 4x8 plywood, and glass from a discarded patio door (thermal pane). Two problems immediately became apparent: first, how to make the panel weather

tight and have little upkeep, and second, the unbelievable weight. It weighed over 400 pounds!

You might choose plastics for the framework of a solar panel because they are light weight. But over the years, plastics have proven to be a poor choice for the major parts of a solar panel. For the exterior, plastic has a nasty habit of degrading from the sun’s ultraviolet rays. Plastic discolors and eventually becomes brittle and cracks. Plastic also has a high coefficient of expansion. This means it expands and contracts so much that making the joints weather tight is difficult.

You might think steel is a good choice because it’s strong, but the few panels I have worked on that were made of steel had two major problems. One, the panels need painting regularly and two, they react chemically with the copper interior. One manufacturer tried using steel for the interior plate (the black absorber), but it took a long time to heat up and did not give its heat up as easily as copper.

There are two ways to construct a panel with aluminum. The first, usually chosen because a do-it- yourself person has the materials readily available, is to use 2x4 lumber and cover this with aluminum coil stock. This is available from lumber yards in rolls two feet wide. Coil stock is the same aluminum used by contractors to make seamless gutters. The most appealing color is bronze, but it can also be ordered in other colors as well as white.

The second choice is to use extruded aluminum. This is manufactured to be the framework without any other materials, such as wood, for strength. All major solar panel companies during the 1970s and 1980s used this method, as it is light, durable, and reasonably easy to use. Figures A and B below show these two methods of building the frame.


Insulation in construction of solar panels and plumbing is very critical. Poorly insulated panels are guaranteed to perform below expectations, so use time and materials wisely. The best material that is easily

End View — Solar Collector Frame


flashing (optional)

Figure A

extruded Aluminum

Glass Thermax


2 x 4

Aluminum Back

Figure B

36 Home Power #40 • April / May 1994

Image | Solar Heating Basics

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