How To Insulate Basement Walls
Insulating a basement properly is rather challenging in cold climates. In this article I’d like to discuss how to insulate basement walls in cold climates.
Insulating basement walls in cold climates is a great way to keep your home warmer and drier. However, special care should be used when insulating concrete (or block masonry) basement walls. Below grade concrete foundation walls are very col and damp. If you were to insulate the walls with regular fiberglass batt insulation it is very likely that a mold problem would develop.
Recommended Basement Insulation
Therefore I recommend using a combination of products to insulate basement walls. In order to create a vapor barrier and separation between the concrete walls and wood framing I like to use extruded polystyrene insulation (blue board from DOW).
Next we frame a traditional wood stud wall in front of the polystyrene insulation. We do take one special step in framing the wall. First we install a layer of composite decking between the concrete slab and the pressure treated bottom plate of the wall. Finally we install some type of insulation in the wall cavities.
Step 1 – Install Extrude Polystyrene Insulation Boards
The first step in insulating a basement wall is to install the polystyrene insulation (for more information we recommend reading: R Values Of Foam Board Insulation). We like to use a all purpose adhesive that’s approved for Styrofoam products. After the polystyrene insulation is installed each of the joints is taped with construction tape (there are several available from Dow, Tyvek, and other house wrap manufacturers) or some other approved tape that adheres to polystyrene insulation. By taping the joints you are helping keep moisture and cold air from infiltrating into the stud wall cavity.
I recommend you seal the top and bottom of the foam board using spray foam from a can. You can buy products like Great Stuff that will seal those joints very well. Be sure that you install foam board on top of the concrete wall up tight against the wall plate and seal that well.
Want to see how this is done? What the following short video: