Here is what the U.S. Department of Energy says on their website-
“Air sealing is one of the most significant energy efficiency improvements you can make to your home. Air sealing will not just reduce energy costs; it will also improve your home’s comfort and durability.”
Simply put, air sealing disconnects your living space from the outside world. When air sealing is properly done, the house must have .35 air changes per hour to ensure that there is an appropriate amount of fresh air in the house. Stated in another manner, the entire volume of air in the house needs to be changed every three hours.
This can occur from natural leaks, such as those around doors and windows, or mechanically through exhaust fans and ventilation devices, but it is very important that it is minimized and comes from a place that we would like it to come from. Would you like the air leak to come from the attic into your house? Most attics aren’t the nicest places to hang out in ( I know, I spend a lot of time in them on a weekly basis and there isn’t one that I’ve found that I’d take my family to for a picnic). But many times, the fact is, air is sucked into the house through insulation and into your living space. So sealing that off not only makes sense from an energy savings standpoint, but also from a health standpoint.
Experts agree that air sealing should take place at the highest level of the house first. After all, hot air rises and creates pressure to escape the house. When it does, it must be replaced by new air, so it will typically suck in air from the low spots of your house. So, if you could seal the high areas so that the air has no path of escape, it will not need to suck in new air to replace its volume.
Think about your refrigerator. It would be easy to keep it at 75 degrees, simply because it is made for that purpose. It is air tight and well insulated. Our houses, here in California are built less like refrigerators and more like cardboard boxes. They leak like crazy. Air sealing is an effort to make your house more resemble the refrigerator in your kitchen. When we air seal your house, the hot air will still rise, however, it will have no where to go. But it gets better, more hot air is being created and rising in your house. As it rises, it pushes the air at the top back down. This is called a convective loop. It is a natural draft loop in your house of hot air rising and falling ( with a leaky house it just keeps rising).
So, with a properly sealed and insulated house you can say good bye to that 5-10 degree temperature difference commonly found in 2 story California homes. How many people have to keep their lower levels unreasonably cold in order to have the upstairs be tolerable? And how much more energy does that use? This can be solved with air sealing and insulation ( for reasons described above, adding insulation alone will not solve the problem, as insulation IS NOT an air barrier).
So, air sealing is important. Air seal the high levels first. Next air seal the lowest levels of the house, this is especially important if your house is built on a crawl space. Finally, insulate at the door and window levels of the house. But, if I could only choose one place to air seal, I’d seal high.
This is one of the most effective ways to create an energy efficient home.