The basic idea here is that the cooler room air is drawn into the lower chamber and warmed as it passes over the black heat collector. As the air warms it rises and enters back into the room through the upper chamber.
The heat collector should be spaced in the center of the box so there is about 3″ to 4″ of space above and below the heat collector. The heat collector could be made from almost any material and painted flat black. A more efficient heat collector can be made from a thin aluminum plate painted flat black, mounted 3/4″ of a inch above a heavy foam board. You can use some 3/4″ shims between the aluminum panel and the foam board.
It is important that the bottom and sides of the box be well insulated to improve air flow and prevent heat loss. It is also very important that the entire box be weather tight to prevent moisture from entering as the moisture will reduce the efficiency of the box. The top of the box should be a clear top, either a sheet of clear acrylic plastic or better yet an insulated window pane.
This is one home improvement project that could help offset your winter heating bills and also help out the environment. This winter I may sit down and try to design one and build it to see how well it works. Some of the more efficient solar box window heaters can produce a steady 120 degree air flow on a sunny day.
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So, have you built one of these yet?
I'd love to have one or two for our cottage. What happens at night? Do you leave it in all the time? Can you leave it unattended, such as at a weekend ski house? I'm interested.
They are self regulating. They will 'shut themselves off at night' as it is the difference in temperature between the lower and upper chambers that make the air flow. This idea was in Mother Earth News in the 1960's- 70's.
@ Campbell - I have not built one yet. I am thinking about building one this winter as an experiment.
Bringing solar heating to any home is a tremendous idea - no matter what form it comes in or whether you bought it or made it yourself. Unfortunately, I'm not a do-it-yourselfer...and not everyone is. For them the choice is to have someone build a window heater - or look for another solution. And one is out there.
Here's the pitch from us.
SolarChoice passive solar heaters masquerade as vertical window blinds. Operating via natural convection, cool air is drawn into the bottom of each vane. Air travels along the sun-heated aluminum core at the rate of 1.7 meters/second and exits the top and re-enters the room at temperatures measured at 120 degrees.
The University of Minnesota helped develop this innovative passive solar heater and works on all product research.
An independent lab (Stork Materials Technology) assigned an R-value of 1.7 to the "blinds" - so they not only heat...but insulate as well. Bob Vila, Solar Thermal Magazine, NPR and Green Builder Magazine have all written about SolarChoice. Every one of their articles is on our web site.
Are SolarChoice Heaters the solar solution for everyone? No. But if you're looking for a heating solution for your home - go solar in some way, shape or form.
A girlfriend had on of these in the late 70s. It worked great. We removed it each Spring.
Hi need a window box heater that has a battery back up for night and gray days. I live on Long Island where if you do not own your own home its like having a gator, if you have a dog or cat. I am insulating a small 8 x 6 shed to house my pets and could use help from a reputable source to heat this. I saw small dog houses that had solar power but nothing for night etc. THANKS MUCH Helen
is the diagram pictured sufficient for a carpenter to build the window heater or are exact blueprints needed.? Also, would there be a problem building a solar heater in a Bay Window mount as far as air flow is concerned?
I think that's sufficient to build one.
We had one of these back in the 70s for a mobile home. We worked nights. By the time we got up in the afternoons the house would be nice and warm. After dark we would use the wood stove, a Crest airtight.