How do you prevent ice dams? Insulate, insulate, insulate! The ideal solution is to fill all roof and wall cavities with blown-in or foam insulation and then wrap the entire house with a layer of rigid foam to prevent “thermal bridging”–the transfer of heat through the studs. That’s fine if you’re replacing your roof and siding anyway. But if they’re in good condition tearing them off to insulate may be expensive and wasteful. An alternative: install rigid foam on the interior. We did just that on the two coldest, draftiest rooms in our house and they’re now our two most comfortable spaces. You do have to pay attention to the construction details to be sure you’re not trapping moisture inside the wall or allowing drafts through wall penetrations like outlets and pipes. Contact us if you’d like to know more.