Air sealing is the act of using a material to stop air from passing between two spaces.
When we look at homes, we want to create a continuous thermal envelope. What this means is that we want to separate conditioned spaces from unconditioned spaces. Your attic that has insulation in it (or should have insulation) is what we call an unconditioned space. Here, you are not living in the attic. You are not heating it, nor are you cooling it. Therefore we want this to be separated as best as possible from the living space. Do you want hot air from the attic to come into your bedroom in the summer while you're trying to live in air conditioning? No! To prevent that, you need a continuous thermal envelope.
Now that thermal envelope we were talking about. If you are upstairs in your home, in a living space, and you look up, you should see a drywall ceiling. Drywall is a material that air seals. The drywall prevents air from passing between your nice, conditioned home and the unconditioned attic. Below is an example of a drywall ceiling with an attic hatch.
What we are looking at is part of the thermal boundary. The attic hatch leads to the attic. We want to keep the two spaces separated. But what happened? The builders created an access to the attic and did not seal it off properly. They cut a hole in your drywall barrier. As soon as holes go in your drywall barrier, air can now pass between those spaces. Look at the the thermal image, air is passing between those two spaces. The solution is to air seal the attic hatch to prevent air from passing between the two spaces.
Below is another example of what happens when you have a break in your thermal boundary. The drywall ceiling remains all one temperature, indicated as yellow in the picture below, but by installing a vent there are now air changes occurring between the two spaces.
Air sealing can be performed in a variety of spaces in the home. They include attic spaces, knee walls, crawl spaces, basements, garage attics, exterior doors, recessed lights, and others.
By blocking air from moving between a conditioned space and unconditioned space, the home will be more comfortable and efficient.
The problem is that you want to make sure the air sealing work is performed properly, targeted in the areas that need it, and that you do not seal up the home too much.
Stay tuned for the next blog post where we discuss the dangers of air sealing.