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What kind of insulation to use for my basement?

Posted by mystiky (My Page) on
Tue, Jun 25, 13 at 10:48

Our newly rebuilt basement is taking shape and soon we will start closing it with sheetrock, meaning that we have to decide on insulation.

The house is all-brick from 1930's here in Brooklyn, NY. It has all new sewers and I have never seen any water in the basement during the few years we have owned the house. The basement goes about 5 feet underground (measured from the inside) The only heating / air conditioning in the basement will be provided by a 9,000 BTU LG HVAC system airhead. I plan to install a portable humidifier that will be periodically on. Summers here are very humid and winters are dry.

A few suggestions were made to me about which type of insulation to use, so I would like to hear some feedback on each method:

1) Using the spray-on foam. But which one? I hear that if it's not done properly, it could create a bad moisture situation
2) Using the standard R-11 that is sold in Home Depot / Lowes
3) Using Roxul's product Comfortbatt (R15/16 or R23):

Also: Will I need a vapor barrier in general?

Any and all opinions are much appreciated!

Follow-Up Postings:

RE: What kind of insulation to use for my basement?

Your choice of insulation is a matter of building science, not opinion. See link.

Your choices are still wide however.

But, first, no fibrous insulation against the exterior wall unless it's on top of foam. You can use closed cell spray foam (ccspf) extruded (XPS) or expanded (EPS) polystyrene foam boards or polyisocyanurate foam boards, either by themselves or in conjunction with fibrous insulation. Open cell spray foam (OCSPF) can also be used but with precautions, as it is vapour permeable.

BSD-103 photo photo_04_interior_basement.jpg

Extruded polystyrene foam board on basement wall.

I've often used the lightweight steel framing you have. A lot easier and cleaner to install than wood and no screw pops later on. The only flaw is that there should have been at least a layer of 6 mil poly under the baseplates to keep rising moisture away from the galvanized. (I actually put strips of 1" XPS under the baseplate.)

The biggest drawback to professionally applied SPF is cost followed by the risk that an untrained applicator mixes an inferior product and/or does not apply it properly.

If this is a diy job, applying XPS boards would be my first choice. But that would have been more easily done before the framing was installed. You now have to slip it in behind a finished wall. Then follow it up with high density fiberglass batts or Roxul rockwool. Also, piece in in XPS boards at the rim joist, caulking and foaming them tight.

Here is a link that might be useful: Building Science Corp.: Basement Insulation

This post was edited by worthy on Tue, Jun 25, 13 at 19:48

RE: What kind of insulation to use for my basement?


Get over to Building

Easiest Homeowner (also more cost effective) will be to go with rigid foam and batt insulation.

Depending on climate location, no vapor control beyond the primed and painted drywall should be required.

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