I have a whole-house fan (attic fan ?), a roughly 3-ft diameter fan that sucks a LOT of air out of the house (and thence out the ridge and soffit vents). It can be nice in the shoulder warm seasons and when I have a merry mix-up with the woodstove or in the kitchen. But, the only thing standing between the loft/cathedral-ceiling area and the cold cruel world is a 3x3ft metal contraption of louvers that automatically open when I turn-on the fan. They seal fairly well, but have absolutely no insulation, and I hate to think what the R-value (or, more to the point, the U-value) is. If I stick my hand up though the louvers, it doesn't feel cold up there, and I'm like "duh, yeah, I'm heating the frickin' attic". So, what to do ? These fans are so common that I can't believe there's no product available. Another option is to build something. I'd build a box of 1x4s surrounding some 1x4 T&G planking (like that on the ceiling) or maybe some furniture grade plywood, with a couple layers of blueboard and a lot of weather stripping. The thing would be hinged on one side. It's in the loft, so I'd have to go up there and open it when I need to run the fan, and of course it'd be in the way at that point. That's the best I can come up with so far. Any better ideas, or a product I'm missing ? Thanks.