Whole House Air Sealing


Whole house air sealing is the first step in making existing homes more energy efficient. Air sealing is the practice of finding the holes, leaks, and bypasses in which air leaks into and out of your home. Most homes leak far more than they should and the leakage occurs into the attic first. Warm air rises and also holds more moisture and this moisture will condense on the first cold surface it hits, and then when it gets warm enough the frost melts, turns to water, and can start turning to mold or rotting wood, so the attic is the first place to start air sealing. After a cold spell in the winter it is a good idea to open the attic hatch and look into the attic. It is surprising how many homes get frost in the attic and it is mostly due to air leakage. Adding insulation on top of what is there without air sealing can make the frost situation worse. The attic must be sealed before adding more insulation. We have been in homes that have had black, green, and yellow mold on the bottom of the roof deck and the trusses and in some cases we have found wood that is starting to rot in attics.

Doing anything to make a home more energy efficient can have unexpected consequences. Safety of the occupants is the first priority. Changing that leaky window or door, adding more insulation, or air sealing can trap carbon monoxide (CO) in the home that was leaking out before. The heating system and water heater should be looked at and maybe tested by someone who has taken a combustion safety class. This should be done before home improvements and after improvements.

The best tools to use to find leaks in a home are a blower door and a thermal imaging camera(TIC). By sucking air out of the home with the blower door, the amount of air can be measured, using the TIC the leaks can be found, the problem areas can be fixed, and another test can be done to verify how much improvement has been made. Air leaks can be large and easy to find visually sometimes but many leaks are hidden and the TIC shows where they are. To seal up leaks we use caulk, expanding foam, rigid foam, plastic and steel sheeting, and other things to stop air movement.

One of the comments we hear a lot is that the home has to breathe. The home does not have to breathe, people do. People also have to breathe through their mouth or nose, not through their elbow or knee. Homes are the same way. The home should be as tight as possible, with the right insulation and then they should breath with a ventilation fan or system of the right size so the occupants can control the indoor air. This is the best way to be more comfortable, save heat, save money, and do it safely.