Chim-Chimney Chim-Chimney...
“Always find and seal air leaks before adding more insulation. Chimneys or furnace flues that penetrate your attic floor have holes or gaps around them that can allow the air in your home to escape through the attic, increasing your energy bill and causing more drafts. Around chimney and furnace flues that can get hot, cover the gaps with metal flashing and caulk small gaps with high temperature caulk. Learn more in the DIY Guide to Sealing and Insulating with ENERGY STAR (PDF, 12.7 MB).”