Air Sealing Basics


Want to save up to 20% on your heating and cooling costs this year? It may be easier – and cheaper – than you think.

Most people are aware that adding insulation and replacing old windows are great ways to make a home more energy-efficient. But they may not be the best place to start. Especially if you have an older home, you may have enough little gaps and cracks in the shell of your home to add up to the equivalent of leaving a door or window open all year! If you’re looking to save energy and money, air sealing the leaks in your home is the easiest and most cost-effective place to start.

Why Air Sealing is Necessary

To really understand what’s going on in your home, you have to know a little about how air behaves. Air moves from areas of high pressure to areas of low pressure – the bigger the pressure difference, the faster the flow. That’s why wind blowing against the side of your house causes drafts. Pressure differences can also occur inside your home. For example, hot air being forced through your ducts is way more pressurized than the air next to the duct. Where there are leaks in the duct you lose air, making your heating system work less efficiently.

Air also moves according to temperature. Hot air rises, and cool air comes in to take its place. This is called the chimney effect – but it doesn’t just happen in chimneys. Your whole house can act like a chimney when leaks at or near basement level draw in cold air to replace heated air leaving through leaks in the attic or roof.

Effective air sealing plugs all the little cracks and gaps, preventing pressurized air from going through and taking your hard-earned energy dollars with it!

Where to Air Seal

The best way to determine where you’re losing the most energy to air infiltration is by having an energy audit done on your home. An energy auditor will likely conduct a test using a blower door – a device that pressurizes your entire home. The test allows them to measure your air infiltration, and estimate how many times per hour that air changes over in your home. The home energy consultant can also help you find the most important air sealing targets – those spots in your home that are letting the most air in!

If you prefer to do your air sealing yourself, here are the most likely places to look:

  • Crawl spaces – seal any leaks with caulk and foam, and insulate the cavity.
  • Windows and doors – Use weatherstripping, caulk and backer rod.
  • Around pipes, vents, ducts, light fixtures and other perforations in the envelope of your house. Use caulk for small cracks, spray foam insulation for larger gaps (but not where it will be subject to heat!)
  • In the attic – Check all around the attic for penetrations in the roof and walls, leaky attic windows, and air leaks around stairs, chimneys and soffits.
  • In the bathroom – Caulk around the water intake pipes.
  • In the basement – Seal leaks in exposed ducts, old coal chutes, unused laundry vents, and any gaps in basement walls or between the foundation and the top plate.

One note of caution: just because a space is insulated does not mean it’s been air sealed. Most insulation does a poor job plugging leaks. Air sealing before insulating will make the insulation much more effective.

All this may sound like a lot of work, but it’s really easier than it sounds. For a small investment and a few hours worth of puttering about filling cracks, air sealing your home could save you $600 – or more – per year!

Related Items