I finally got around to putting the insulation over the attic fan, and this year I also put a plastic stick on cover over it. WOW, what a difference. We've had to run the wood stove less and when we do the upstairs gets a lot warmer. I didn't realize how much I was loosing due to stack effect and the friggin hole. Also plugged up the crawl space vents (as per the building sciences reccomendation) and insulated the holes...another WOW. All that plus the newly insulated basement, and with the temps hovering around 35 out, the darned house is near 80. Nice simple fixes can mean a big difference. I encourage everyone to find the holes and plug them.