You already know the basics of sealing: you do it every time you zip up your jacket or lift your collar against the wind. Sealing a home works on the same principle, reducing air infiltration through the walls, ceilings, and floors to save energy and stay comfy. Just as you do a jacket, it’s best to button up – or seal – the shell of your home, or the “envelope,” as the exterior of your home is called in trade parlance. Older homes may have had no sealing done at all, and not all builders of new homes do a great job of sealing a house, even when sealing is required by today’s energy codes. We researched the best products and spoke to several experts to learn how to tighten the envelope of your home, save energy, and keep out the cold.