Living in Oakland, CA during the hottest stretch of the summer can be uncomfortable. Many homeowners turn straight to their ACs, which help to create conditioned air that keeps us cool on even the hottest days of the year.
Even if your home is fully insulated from the attic down to the crawl space, it still most likely suffers from excessive air leakage that robs energy and harms comfort. Building code enforcement is beginning to embrace the need for sealing air leaks in the home, but this is not yet universal. Conventional thought in the building industry is that insulation is all that is needed to keep a home warm in winter and cool in summer, but fiberglass, the most common insulation material, does not stop air movement. Just like you need a windproof parka over your fleece jacket, insulation does not do its job without a continuous air barrier between the insulation and the inside of the home. In fact, typical homes Hassler tests for air leakage in the Bay Area leak more than twice the amount of air they should!
Even though, standing inside our home, it appears that the drywall makes a continuous seal across our ceilings and the finished floor is continuous, the reality is that the ceiling and floor systems have gaps built in them between framing and finishes, and installing plumbing, electrical, and heat in a home creates additional holes in the air barrier.
Here are some common places where leaks in the air barrier are found:
- Wall “top plates” between the wall framing and the drywall
- Electrical wires where they exit from the wall into the attic or crawlspace
- Electrical connections at light fixtures made inside the attic
- Plumbing supply lines entering a wall through the crawlspace
- Plumbing vents protruding through the wall into the attic
- Drain pipes under bathtubs, toilets, and sinks
- Cut-ins for duct registers
- Dropped cavities above cabinets and fireplaces
- Chases for plumbing, ducts, and other building infrastructure that run from the crawl space all the way up to the attic
All the individual holes from each of these different locations add up to a lot of leakage. In most homes, the amount of leakage from these unintentional sources is equivalent to having a window open all the time! During an energy audit, Hassler tests air leakage using a blower door, and can tell you exactly how much air your house should exchange, how much it actually does, and where excessive or unwanted leakage is occurring.
Not only do these holes leak out the air you pay to heat or cool, they also leak dirty air in from the crawlspace and attic, which could contain fiberglass particles, rat feces, sawdust, mold, asbestos, and other contaminants. By sealing off these leaks, the air inside the home becomes healthier as well as more comfortable and energy efficient.
Air draft sealing is a low-cost project that can be completed usually in a day or two. Crews use expanding foam and rigid materials to cover and seal holes from inside the crawl space and attic. Air sealing should almost always be completed before installing insulation, because insulation can’t do its job well if air is leaking through it, and it’s much easier to complete the air sealing if insulation has been removed from the place where the air sealing needs to occur.