Question

We need a safe and effective way to insulate our basement concrete walls. Which wall stud configuration and insulation are recommended?

Asked by Rachael
Riverside, IL

The concrete foundation walls in our 1930s home in suburban Chicago are damp. The walls have leaked in the past, so we had epoxy injections to repair a few cracks.
We are planning to renovate our basement to use as a family room. We've researched online and found a recommended wall construction type is to use 1" rigid foam directly on the concrete walls, with taped joints to act as the vapor barrier. Then, build the stud wall in front of the foam with batt insulation in between the studs. We have also heard from a couple of contractors that we don't need the rigid insulation, but just need to leave a 1" gap between the concrete wall and stud to allow the concrete to breathe.
We have used cellulose insulation on another renovation of our home and prefer a green method of insulation. Which type of eco friendly insulation and wall construction is recommended for basements in our climate?

Answer

Answered by adam hillhouse

windsor, CO

Hillhouse Architects, Inc.

March 12, 2010

Are your concrete walls still leaking? You mention some epoxy injection, but not the result. Have you had any further leaks? You will need to fully address this prior to moving forward.

Condensation will form on the warm side of the wall (finished side) so the moisture barrier needs to be installed nearest this side, with the cold side allowed to breathe.

You want to make sure you don't have a vapor barrier on both sides of the wall as this could trap moisture in the assembly.

Batt insulation comes with a vapor barrier on one side (foil faced) but it would be most effective to also place a min. 4mil thick barrier (plastic) over the studs before hanging drywall. Vinyl wall coverings are another affective VB.

I'll have to let others comment on specific assemblies for your location.

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.