Basic physics tells us that heat travels from hot to cold. So in the warm summer months when you are using the air conditioner to cool the air in your home or building, the stack effect reverses direction. This reversal pulls hot, dusty attic air into your home through unsealed penetrations.
Common penetrations include recessed canned lights, thermostat wiring, plumbing chases and bathroom exhaust fans. The dust you wipe away each week has traveled from the attic through these penetrations and will continue to do so until the problem is put to rest. Now, don’t be discouraged! There is a simple solution that is also cost effective: Air Sealing. By air sealing those penetrations, you will reduce the air flow between the attic and living spaces in your home and you won’t have to breathe that dusty attic air anymore! Now get up there and get dirty, you’ll be glad you did. . . . . . . . .
Check out the DIY Guide to Air Sealing and Insulating with ENERGY STAR: https://www.energystar.gov/index.cfm?c=diy.diy_index