Frankly, I don't see how, if the vents are properly insulated, it would not help to heat a room on a sunny day. I understand that it won't do a thing at night or on a cloudy day, and at those times we will be forced to heat with our oil furnace. Fortunately, we do have lots of very cold, bright sunny days in the winter. Sure this won't do everything, but any help it offers will help me buy less fuel oil next winter and increase my payback.
We're waiting for an evaluation appointment with the other solar installer. I am sure I will learn a lot from the visit, but I don't know whether what I learn will change my position that solar hot air makes sense. Even more so after learning that the State rebate fund is quickly disappearing. My application has been submitted, but I don't have a reservation number yet (so no guarantee that I'll get a rebate).
I suppose my next consideration will be to improve my home insulation/envelope. I have good attic and basement insulation. My problem, I believe, is my windows. They are 15 years old, double pane, but made of wood that it showing it's age. Seals have gone on all of them. I have been replacing the glass, but I am spending a lot of time putting lipstick on a pig-- the wood frames are shot. Unfortunately, new windows are pretty expensive.
After listening to an NPR broadcast about Martin Luther, Bert was inspired and observed that paying for carbon emissions to feel OK about flying around the world, living in a 4000 sq ft. home, or driving in a Hummer are payments for carbon indulgences, not carbon offsets.