It just drives me crazy! When you see news stories in the media about improving your home’s energy efficiency, they invariably tell you to caulk your windows and weatherstrip your doors. There are enough home energy pros now that we oughta be able to cure the media of foisting this uneducated advice on homeowners. Instead, it lives on as one of those self-perpetuating beliefs that resurrects itself every year and won’t go away.
See that photo above? That’s just one small section of a gap that allows attic air to move right down into the walls of this house (or from the house into the attic). The whole thing is probably 20′ long and adds up to many times more infiltration than this house (or just about any other) gets through all the windows or doors. The discolored insulation shows that air has been moving through that gap.
That’s probably the biggest source of air leakage in this house, but there are plenty of others. The photo below shows a gap between the top plate and ceiling drywall, and light comes straight through from the room below because that corner was never taped and mudded. Why? Because there’s crown molding there, of course. Why waste labor and materials in a place where it’s unnecessary? Well, that was probably their flawed thinking anyway. (The light was coming through because the crown molding had been removed there.)
Actually, even without crown molding, unsealed gaps at the top plates can produce a lot of air leakage in a house. When someone does a Blower Door test to determine the infiltration rate of a house, you can walk around and feel the air blowing through receptacles and switches—even on interior walls—because of those unsealed top plates.
So, before you go around caulking your windows and weatherstripping your doors, get up in your attic and seal the real leaks! And you definitely want to air seal the attic before you add insulation. Otherwise, you’re covering the leaks with material that will simply filter the dirt but not stop the air movement.
Another way to eliminate those air leakage sites in the floor of the attic is to make them irrelevant. The photo above shows spray foam insulation on the roofline creating an encapsulated attic. That made the ceiling (attic floor) an interior partition and brought the attic inside the building enclosure. So the attic is now part of the conditioned space.
Allison A. Bailes III, PhD is a speaker, writer, building science consultant, and the founder of Energy Vanguard in Decatur, Georgia. He has a doctorate in physics and writes the Energy Vanguard Blog. He is also writing a book on building science. You can follow him on Twitter at @EnergyVanguard.
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