Air sealing your home is often touted for its heating-bill-reducing properties in the wintertime. Less often does the average homeowner think of air sealing as a concern in the warmer months. The truth is, having a properly air sealed home is equally important in the spring, summer and fall, for a number of reasons. This article explains them.
The benefits of air sealing are, to reverse the common expression, many and close-between, and include everything from protecting your home's structural integrity to protecting the cookie jar from invading pests (although that doesn't include the kids next door). We, however, will stick with the fundamentals:
Summer airflow dynamics, and the main culprits:
Our main article on air sealing discusses something called the stack effect, or chimney effect, which describes air movement through a house in winter. In an air conditioned house in warm weather, the process is reversed, and works like this: cool air is denser than warm air, so it sinks as warm air rises. As you cool the air in your house, it gradually sinks, down through air leaks onto the first floor or into the basement. As the cool air sinks, it's replaced by warm air from the attic, which is pulled in through air leaks in the thermal envelope (which separates the attic from the top floor).
To soften the impact of the reverse stack effect, focus most of your air sealing energy on the attic floor (to seal the thermal barrier between your living space and the attic) and the basement. The basement is often the leakiest part of the house because of plumbing and electrical conduits that penetrate walls. And use the spider test: spiders build their webs at the site of incoming air where they can pounce on incoming morsels. Where you see spider webs, there's typically air flow.
Another major air leakage culprit in an air conditioned house is the duct system that distributes cooled air throughout the house. Duct leaks are often difficult to find, which is why it's a good idea to have a duct blower test conducted as part of an energy audit; but pinpointing and addressing leaky ducts could save up to 25% on air conditioning costs.
Don't forget, though, that there could be some substantial air leakage going on right under your nose - around windows and doors, along baseboards, through electrical outlets, etc. Those small leaks add up. See our buyer's guide to find the right tools for any air sealing job.
Now, here's why air sealing is useful in the summer months:
Increases occupant comfort:
Air leakage accounts for 20% of summer heat gain. We tend to think that holes letting air in will produce a cooling effect, the way rolling down a window in a car on a hot day will. Truth is, it just doesn't work so nicely. Rather than creating a nice strong breeze on a hot day, the small, scattered leaks around your house let hot outdoor air slowly seep into your nice cool house.
Moreover, they take away your power to control your home's ventilation. Ventilation is a wonderful thing, but you want to be able to control when and where your house is ventilated - whether you have a full-house HVAC system, exhaust fans, or just windows and air circulators. A leaky house is an out-of-control house. The first step toward making your home comfortable and efficient is taking control of leaks.
Saves energy (think: saves money):
If you live in an air conditioned house, air sealing is essential in order to avoid cooling the great outdoors (and no, you won't be able to keep the polar ice caps from melting, so forget about it). Air conditioning is expensive and environmentally, well, unfriendly - so when we use it, we want the benefit to be ours.
Health and safety: Indoor air quality and pests:
Partially related to moisture control is the question of indoor air quality, since moisture carries biological contaminants such as mold. Aside from moisture, even common building materials like particle boards and glues often contain chemicals that are best kept out of your lungs. Sealing leaks - ideally with a water-based, low-VOC, non-toxic sealant - will keep harmful chemicals at bay.
Air leakage presents another problem in the warm months that we tend to forget about in the winter: Bugs. Creatures. Pests. They'll eat your food and scare your children if they're not stopped.
Prevents moisture infiltration:
Moisture control is particularly pressing in the spring and summer, when basements are prone to flooding and relative humidity is at its highest, respectively. Moisture in your house brings a whole slew of problems, which include, but are not limited to: compromise of insulation, building decomposition, wood warping, metal decomposition, and mold.
While air sealing will protect against liquid moisture (rainwater), the more pertinent concern is moist air - both humid summer outdoor air, and moist indoor air from the basement, the attic, and from indoor sources such as showers and ranges.
So...
Although air sealing is one of the most cost-effective ways to reduce your winter heating bills, it's not just a seasonal worker - so you shouldn't be either. Besides, what better time to do some air sealing in your home's nooks and crannies than during spring-cleaning season, when you're diving into those nooks and crannies anyway? And who wants to work down in the basement, and up in the attic, with purple fingers? So go ahead, right now, grab a good caulking gun, load it up, and dig in.
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