nice set up. Offgridguy. tho i suspect we're going off topic.
verdigo. for my "shizzer shack" (high tech washroom) I'm trying passive solar venting.
to wit: I have a metal roof. beneath that are the battens. then sheets of foil faced polyiso, then the rafters. What happens is that the sun heats the air between the insulation layer and the metal roof. What happens to hot air, it rises. The hot air is then vented out through the ridge. It draws cooler air up from the outside edge.
Now I'm just letting it work like that to reduce heat coming into the washroom. But in one of the posts I found the researcher (sorry, thought I had the link, but...) cut holes in the polyiso down by his walls. This allowed the convection current to draw air from his attic (in his case) up through to the vented ridge. This reduced his attic temps from 140 to 80 (if memory serves
).
I can say that the system works. I don't have documented temps, but shortly after finishing the roof we had a day where it was -2C (about 29F). With two large windows on the south wall of the shack the interior temp of the shack rose to 7C (42F). Perfect for me. I want solar heating. But on the north side of the shed the snow which had fallen during the night remained frozen on the roof. The only explanation is that the convective current was keeping the metal roof at below freezing.
Rather than a fan you could harness the same principal for passive solar cooling. I recommend it to anyone trying to cool their house.