Today a client asked a question common for this time of year:
“My house is very drafty in the winter, but I can’t afford new windows right now. What can I do?”
First, you should have an energy audit performed, complete with a blower door, to measure how much air leakage you have around your windows. Spoiler alert: it’s probably not much.
When we do the blower door test, we depressurize the house to determine how much air is infiltrating the home from the outside. We can then use a thermal camera (or simply walk around the inside perimeter of the house to feel air coming in). You might be surprised to learn that windows are typically not the problem. Most air leakage is usually through plumbing and electrical penetrations, behind crown molding where the wall meets the ceiling, laundry room hook-ups, and several other places most people never think of.
So, why do we get this question only in the winter-time? Because of the transfer of heat: high heat always flows to low heat. In the colder months, we walk by the window and think we feel a draft of cold air coming in. What we are *actually* feeling is the heat leaving our bodies and transferring to the cold window.
Looking at the first thermal image, where I am waving in the window. The surface of the window is 55.6 degrees, much colder than me, where the heat is leaving my body and being absorbed by the window.
Now look at the second image. The cross hairs point directly at the image of my head, and the window is 4.3 degrees warmer. The heat from my body is transferring to the cold window. The temperature differential must be significant to notice this effect. On this winter day, the surface of that window is about 43 degrees colder than I am. This explains why we never get the question in the summertime.
What to do? The good news is that you probably don’t need new windows. In fact, the easiest fix is to close your curtains or blinds. Storm windows are also a relatively inexpensive option. An energy audit by a certified energy professional may help identify other issues contributing to the cold, such as a leaky duct system, lack of insulation, air infiltration, etc.
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Author: Chris Kell | RESNET Certified HERS Rater | BPI Building Analyst | Energy Star 3.1 Certified