Basement Wall Insulation Question

Pigonahog

Hello all. I'm framing my basement and I plan on framing along all of my cement walls. However, the contractors who built the house, insulated the walls already. There is a white plastic covering a pink insulation which is all fastened to the cement wall with what appears to be a nail and a plastic type washer. The question is this: Should I take this insullation down and frame the bare wall, then insulate my self? Or should I leave theirs on and frame an inch or so away from the wall? Any help/advice would be helpful. Thanks in advance for your time.

Gary in WA

Pull it, remove the plastic and put it in the attic; http://www.buildingscience.com/docum...lation-systems

Gary
PS. Try a "Search" in the white box top of every page...

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Pigonahog

Will do. Thanks for the reply.

Gary in WA

You're welcome. Lot of good reading; http://www.buildingscience.com/docum...study-analysis

What is the closest city to you?

Gary

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Pigonahog

Brighton is the closest city. Its about 20 miles north of Denver.

Beepster

Do you mean pink FIBERGLASS insulation or pink XPS BOARD insulation?

B

michaelcherr

Re-read the hyperlinked file. Look at figure 13 &14 and table 2.
Maybe i misunderstood the question, but I think he would be best removing the vapor barrier, taping seams in the rigid insulation and either adding furring strips or 2x4 framed walls to attach drywall.
In my opinion (which the linked file agrees with)exterior insulation is best, but interior rigid foam is acceptable practice if other details are done right.

michaelcherr

Edit: I assumed the pink insulation was rigid extruded insulation which is normally pink or blue. If it is fiberglass, take it down.

Pigonahog

Thanks. It was fiber glass covered with a plastic and nailed to the cement wall. I took it down and put it up in my attic. I replaced it with some foam board and will frame over that and add the typical fiber glass insulation between the studs. That should more than suffice. Any thoughts?

Gary in WA

You may need to do additional work due to the heaving soils if locally...

Brighton's average low for D, J., and Feb. is 14*F. At 70* room temp., w. R-5 (1"f.b. XPS), the cavity side of fb will be 30* with R-13 in 2x4 frame wall. At 22% Relative Humidity and above, moisture will condense there, possible wetting the f.g. insulation and degrading it's R-value 60%; http://archive.nrc-cnrc.gc.ca/eng/ib...ling-heat.html

With R-10 XPS and f.g. (R-13) expect condensation at around 32% RH on f.b. near "frost line" and above grade w. f.b. temp. at 38*F.

Could you walk us through the framing/insulating steps?

Gary

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laser_jock

buildingscience is a good resource - i read a lot of their work before starting my basement finish in Lafayette CO. I was very glad to find out that vapor barriers below-grade are a BAD idea before i started building (sad though about all those older basement finishes with mildew and water trapped between the poly vapor barrier and the concrete - seems obvious now that the goundwater moves through the concrete).
Anyway, i also built with the 2" blue rigid foam Liquid-Nailed to the concrete, then framed out 1-1/2" away from the foam with 2x4 stud walls (floating). With 2x6 batts and the 2" foam the R value was about 31.
There was one hitch from the building inspector - he was familiar with this type of construction, but he required a fire stop every 4' to cover the 1-1/2" gap between the back of the stud wall and the blue rigid foam. i used 4" wide strips of sheetrock nailed to the side of every 3rd stud, and pressed tight against the foam.