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Over the last couple years, I’ve wondered why our master bedroom was on average about 10°F cooler than the rest of the house during the winter. At first, I thought it had to do with poor insulation or that the central air registers in that bedroom were not supplying enough warm air from the furnace. Turns out cold air infiltration was the culprit and it was seeping into our bedroom from two locations.

Air infiltration is a bad thing. No matter how much insulation you have, cold air infiltration leaking into the house will cool it down considerably and quickly. In our case, we had cold air infiltration seeping into our master bedroom from two places. The first and most noticeable was through the windows. Melody Homes (now called D.R. Horton) installed the crappiest, lowest grade windows they could get their hands on when they built the house. Embarrassingly, it took me two years to realize that snow pilling up on the inside track on the window probably wasn’t normal. I figured this was probably the first thing that needed to be upgraded, not replaced. I’ve ordered 5 new very expensive windows for the room and they should be installed late February. They are made by Champion and have had very good reviews. I was also very impressed with the demonstration.

The second place the air was seeping in was less obvious. It was actually coming in from behind the baseboards located on the exterior walls (we had two of them). When I removed the baseboards, I could feel a rush of cold air whenever the wind blew. There was about a 1/2 inch space between the bottom of the wall and the sub-floor. My solution was to use the air-tight expanding foam for window and door seals and spray it in the empty space. Careful, that expanding foam is very messy and you don’t need a whole lot. It expands … a lot.

UPDATE: The windows have been installed and there is an improvement. The room is about 4 degrees warmer than it was before. I still think there is an insulation problem and I’m going to have a home energy audit performed this spring. They cost about $400 but hopefully it will help us find ways of improving our home’s efficiency.

Related Topics

• Insulating Ducts

Air infiltration occurs when air from outside finds its way inside your house. This can be a big deal in the winter when the dry chilly air outside is 15°F and the warm air inside is a nice 68°F. Or in the summer when the hot 100°F air finds its way into your cool living space inside. In either case, you can expect higher heating and cooling bills if you have a lot of air infiltrating into your home.

There can be numerous locations in a house where outside air can infiltrate inside. Even more so in older houses, which are more often than not less efficient than newer homes. One place I noticed a fair amount of cold air infiltration was in the light switches, wall outlets, telephone jacks, and my CAT5 networking plugs that were situated in exterior walls. Even though there is insulation in the walls, it won’t necessarily stop the air when the wind is blowing. In my case, during the very cold winter snaps, I could feel quite a bit of very cold air blowing right out of the plug or switch and into the room.

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 coming in through the plug. I have these on all my plugs and the air has been completely stopped. For the light switches, you can try to use a foam insert specifically designed for this, but I found them virtually useless. They did not help at all. The other option, which I did try, is using a can of expanding foam to seal the hole in the electrical box where the wires enter, but this can be tricky.

At Home Depot or any hardware store, you can find cans of expanding 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, for 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. 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 will almost have dried. 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 some more of the expanding foam in there.

Since you really can’t save that can of foam for later use, it’s best to find other places where the foam may stop air from infiltrating inside your house. Here are some other places to look:

• 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 floor

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 also 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.