Using the handy dandy temperature gun someone recommended in another thread, I have discovered that I have a couple of major air leaks into my attic. The first is the recessed lights, which apparently aren't IC and can't be covered with insulation. How stupid is that? I'll replace those.
The second is the bathroom vents. I measured the ceiling at 79 degrees about 2 feet away but the grill measures 94 degrees! I know that these are required by code, but we never use them. They're incredibly loud and they don't do much. I was thinking about pulling off the covers, shoving in some insulation, sealing them off with some carefully cut and taped cardboard, disabling the switch, and putting the grills back on. Aside from the fact that I'll be going through a lot of hassle for not much gain, is there a problem with this approach?