Something you might not know about your basement

Inside basement wall thermal image. The area outlined in the box is the same as the outlined area of the exterior image
Thermal image of uninsulated basement wall from outside. The area outlined by the box is the same as the area outlined in the interior thermal image


Did you know that your 8 inch (200 mm) of concrete basement wall has about the same insulation value as a single pane of glass? Take a look at the thermal images of a 1951 bungalow with insulated basement walls. Comparing the temperature of the concrete and the windows, we can see that the windows are actually slightly cooler, the windows are not transmitting as much heat as the concrete. That is because they are double windows, with an R value of about 3, compared to the the concrete’s value of about 1. The upper part of the house is 2X4 studs sheathed with lumber coated with stucco and rock wool insulation between the studs, with an R value of about 12.  The ambient outside air temperature was about -1 outside, and the indoor temperature in the basement about 19.

New homes typically have 6 inches, or 150 mm of fiberglass insulation on the basement walls, but not that long ago few homes were built with uninsulated basement walls. In the 1970’s builders insulated the part of the basement that was exposed, based on the theory that the soil and ground cover provided adequate insulation for the concrete below grade. While it is true that soil temperatures are generally not as cold in winter as the outside air, it is also true that soil temperatures are almost always considerably less than what is considered a normal indoor temperature. This can be seen in the interior thermal image, the warmer appearing wall on the left is drywall fastened to 2X3 studs, with an approximately 2.5 inch or 35 mm air gap.  The drywall temperature is about 18 C, the exposed concrete 12 C and the concrete below grade is between 13 and 14 C.

In Edmonton soil temperatures are about 10 C below the frost line (about 6 feet or 186 mm below the surface). It is always a good idea to insulate your basement, as your basement is inside the building envelope, or the inside of your house that is heated by your furnace. Allowing any part of your house inside the building envelope to get cold can lead to excessive humidity in cold areas, condensation and possible mold growth.  If you would like East Side to inspect your home and basement, call 780 477 2666 and make an appointment.