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.

Ungrounded Main Electrical Panels

Older homes in Edmonton use or once used metal water supply pipes, made of copper, galvanized steel or even lead piping to bring water into the house from the city water main.  If they need to be replaced, these pipes will be replaced with plastic water lines.  (We are talking only about the pipe that carries the water into your house up to the water meter.)  The problem here is that older houses with metal water lines traditionally used the water line as a ground for the main electrical panel.  When a water line used for ground is replaced with plastic, a new ground connection, directly to the ground, will have to installed, or a potentially dangerous situation exists.

Loss of grounding through water line replacement is mainly a concern with older houses.  Newer houses no longer rely on water lines for grounding the electrical panel, and have dedicated ground rods or ground plates buried in the earth.  Proper earth grounding may also be an issue for mobile homes, ‘off the grid’ cabins with generators or solar panels and outbuildings such as detached garages that receive power through a branch circuit.

If you live in an older house where the water line has been replaced with plastic, you need to make sure that your main electrical panel is properly grounded.  An electrician or a qualified and licensed home inspector will be able to tell you if you have a properly grounded main panel if you do not know what to look for.

The picture below is an example of a ground connection for an electrical panel that is no longer a ground connection.  The bare copper wire goes into the main electrical panel and is fastened to the inside of the panel and the neutral wire.  The green wire is a telephone system ground wire.  Both used to be bonded to a probably galvanized incoming water line, since replaced with the green plastic water line that can be seen in the lowest part of the picture.  Neither the electrical panel or telephone system is properly grounded anymore.  A special CSA approved ground plate or ground rod will have to buried at least 600 mm deep in the soil and connected to the neutral bus in the main electrical panel to correct this situation. The existing ground wires will need to be bonded, that is, electrically connected to the metal box of the electrical panel using a ground screw inside the panel.