Air infiltration occurs when outside air finds its way inside your house. Most people notice this in the winter when cold air blows through a wall outlet on an exterior wall. Or in the summer when the hot 100°F air finds its way into your cool inside living space. You can expect higher heating and cooling bills if you have a lot of air infiltrating into your home.
There are numerous locations from which outside air can find its way inside. Even more so in older houses, which are not as tightly sealed as newer homes. One place I noticed a fair amount of cold air blowing into our house was through the light switches and wall outlets situated in exterior walls. Even though there is insulation in the walls, it won’t necessarily stop the air from entering your house when the wind is blowing.
For the wall outlets, there is a very easy solution. I would highly recommend buying the plastic childproof outlet plugs that insert into the wall outlets. They are a bit difficult to pull out (by design), but they do the best job and completely stop the air from blowing in through the plug. Make sure you get the childproof plugs that completely cover the whole outlet. I have these on all my exterior wall outlets and the air has been completely stopped.
For the light switches, you can use a foam insert specifically designed for this, but I found them to be ineffective. The other option, is using a can of expanding foam to seal the hole in the electrical box where the wires enter, but this can be tricky.
Most hardware stores carry cans of expanding polyurethane foam for this exact purpose. The foam I used is called Great Stuff. It comes with a small flexible straw that allows you to squirt the foam in difficult to reach places. You only need one can, and a little goes a long way.
Grab a lot of paper towels so you can lay the can on something other than your floor because the can oozes once you start using it. Wear gloves because it’s very hard to get the foam off your skin.
Simply remove the outlet plate cover and deep inside the electrical box you will see where the wires enter. The wires can be crammed pretty tight inside the box so you might need to pull them out a bit to gain access to the hole.
The hole is usually in the top or bottom of the electrical box. This is most likely where the cold (or warm) air is infiltrating from. Put the straw from the expanding can of foam just inside that hole and give it a little squirt. The foam may come out slow or it may come out fast so be careful.
You won’t need much, so only fill the hole with a little bit (about the size of a quarter). Wait about 1 hour and you will see the foam has expanded quite a bit and should be dry. If it has blocked that hole, you are done. Put the cover plate back on and see if you still feel the air. If the hole isn’t plugged, squirt in some more expanding foam.
Since you really can’t save the can of foam for later use, it’s best to find other places where the foam may be of benefit. Other places to look are:
- Wires entering house (DirecTV, Cable, Phone)
- Pipes entering house (Sprinkler, City Pipes, City Gas)
- Around the clothes dryer vent
- Behind baseboards where drywall meets the subfloor
The other place I noticed a lot of air infiltrating into the house was on the second story behind the baseboards. If you pull the baseboards from the wall, you will see a small 1/4″ gap (maybe bigger) between the drywall and where the floor is. I used the expanding foam to fill in this space. When the foam dried, I used a utility knife to cut away the excess foam and replaced the baseboards.