Insulating Concrete Basement Walls

It is important to Insulate Basement Walls Properly before Finishing your Basement

By Mark J. Donovan

If you have plans to finish your basement then it is important to first eliminate any water or moisture problems in the basement, before insulating the basement walls. Insulating concrete basement walls can be done both on the inside and the outside of the foundation, however insulating exterior concrete basement walls is best done when building the home. This said, it can be done, but it just will just cost you more time and money. Insulating concrete basement walls is an easy do it yourself project however it is important to wear proper clothing when doing so.

To insulate interior concrete basement walls many builders start by attaching a vapor retarder, a.k.a. vapor barrier, to the concrete basement walls.

If you prefer to attach a vapor retarder directly to the concrete basement walls, make sure to use duct tape on the seams to create a tightly sealed vapor barrier.

Once you’ve installed the vapor barrier, you essentially have one of three paths that you can go down for insulating concrete basement walls. One path is to first install rigid foam insulation up against the concrete basement walls, and then build 2×4 stud walls up against the rigid foam insulation. This way you can then install additional R-11 rolled or batt insulation (3.5” thick) in the wall stud bays to create effectively two layers of insulation. Most 1” rigid foam insulation has an R-Value between R-4 and R-8. Add this to the R-11 rolled or batt insulation and you have a total R-Value level of R15 to R19.

Another path you can go down is to simply frame up the wall studs directly up against the basement walls, forgoing the rigid foam insulation. You can then install R-11 insulation in-between the vertical wall studs.

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Finally, you can attach furring strips directly to the concrete basement walls and then insert rigid foam insulation in-between the furring strips. The furring strips are essentially 2×4 wall studs positioned on their flat side and fastened to the concrete basement walls. You can attach the furring strips to the walls using a hammer drill and Tapcon anchors. In addition, you may want to use a bead of Liquid Nails on the back of the furring strips for a better hold. However, there is no point in using Liquid Nails if you choose to attach a vapor barrier up against the concrete basement walls.

When insulating concrete basement walls it is very important to add a vapor retarder over the insulation and framing stud walls or furring strip. If, you chose to use a faced insulation between the wall studs you do not need to add the additional sheet of plastic to form the vapor retarder.

The faced paper is the vapor retarder. Just remember thought to have the face side (paper side) of the rolled insulation facing inwards toward the basement.

Whether insulating concrete basement walls, or any other space in your home with fiberglass insulation, make sure to where full body clothes protection as well as a mask, gloves and goggles. Fiberglass insulation is irritating to the eyes, throat and skin.

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