One of the most important steps in the process of making your home energy efficient as well as comfortable is to air seal the house first. Simply insulating the envelope (or shell) isn’t enough. In fact, the ability of insulation to perform is almost cut in half if you don’t air seal first. Sealing up air leaks where air infiltrations occur is a tricky business since leaks are usually hidden from view. Air infiltration can simply be under a doorway where there’s not a sweep installed or the threshold isn’t adjusted properly. However, the most common infiltration paths include access to the attic and any air that can enter the home’s envelope from the attic space.