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Basement Finishing

I am building a new home in zone 4, Shelbyville, Kentucky. This is my house plan:

I am using the tremco basement waterproofing system and using a board on the outside which we carry the water away down to the footer and insulate to a value of R5. The basement slab will be insulated with foam board under the concrete floor. I am finishing the downstairs with drywall and wall studs. Since there is R5 insulation on the outside of the basement wall, should I insulate inside the basement as well? If so, what insulation do you recommend? I have seen foam board recommended to be placed against the wall, then 2x4 frames be put up over that. Will the outside board keep condensate off the wall in zone 4? Foam board inside or no foam board?



Asked by Aron Robinson
Posted Nov 6, 2012 5:51 PM ET


6 Answers

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In your climate zone, the code calls for a minimum of R-10 basement wall insulation, so you need to add some more insulation on the interior of your wall.

This article will tell you everything you need to know: How to Insulate a Basement Wall.

Answered by Martin Holladay, GBA Advisor
Posted Nov 6, 2012 6:17 PM ET


Thanks martin...I thought as much. Tremco does make an external board that is r10. Would you recomend I go with that or simply put my money into more internal insulation?

Answered by Aron Robinson
Posted Nov 6, 2012 7:00 PM ET


As long as you are insulating on the outside anyway, I think it makes sense to choose the R-10 product.

Answered by Martin Holladay, GBA Advisor
Posted Nov 7, 2012 6:48 AM ET


Martin...if I use the r10 product on the outside...how should I finish the inside? More insulation...xps for example...then studwall and drywall or just studwall and drywall? Don't want to have mold problems as a result of condensate. What do you recommend? Aron

Answered by Aron Robinson
Posted Nov 7, 2012 12:52 PM ET


If your concrete wall is adequately insulated on the exterior, you don't need interior insulation. You can just install studs without any insulation if you want. (However, an interior layer of rigid foam between the concrete and the studs won't do any harm.)

Resist the temptation to fill the stud bays with fiberglass batts. Just leave the stud bays empty; the purpose of the studs is to make it easier to run wiring and to have something to attach the drywall to.

Assuming you choose not to install any interior insulation, you should still leave a one-inch air gap between the concrete and the studs.

Answered by Martin Holladay, GBA Advisor
Posted Nov 7, 2012 12:57 PM ET


Thanks Martin! This information is extremely helpful.

Answered by Aron Robinson
Posted Nov 7, 2012 9:50 PM ET

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