Thanks for your great website.
Here are my thoughts:
Most folks don't insulate the windows in their homes at night like your
garage door conversion. One can build a 32ft^2 solar air heater for <
$00, or a temporary sun space for even less / ft^2. Putting a 32ft^2
window into an existing south wall is much more expensive. I think an
additional benefit is the active solar air heaters do some
destratification as well, depending on the location of intake and
In my case we have an old brick home with stucco and plaster, our 1446
ft^2 of walls are only about R2.6. Our first 32 ft^2 R7 heat panel
gives a 24hr average of ~R16 counting 4 hours of sun at ~R50. I think
the 32^ft of R16 ups the average R of our walls to R2.9. So there is a
significant reduction in heat loss along with window like heat gain,
per collector. Corrections to my algebra are more than welcome.
- cameron, Alamosa CO.