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Old 02-08-2012, 10:55 PM   #1
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Basement insulation scenarios I'm considering


I have an aproximately 6 month old home in the tip top of Kentucky with an unfinished basement that I'm planning to finish in the next year. It's a poured foundation that's totally underground except for the top 18 inches or so. It has R-5 insulation under the slab with a vapor barrier and Delta-MS dimple membrane for waterproofing. The only insulation is the standard R-13 FG batts in the rim joist bays and R-11 FG covering the top 4 feet of wall. Other than some rim joist condensation that I'm handling with a dehumidifier and switching to XPS, the basement is dry.

The rims and sill plate are going to get 2 in XPS, Great Stuffed in place with the existing R-13 over that.

On the rest of the walls I'm undecided between 2 inch XPS, taped, Great Stuffed, etc. That would net me R10, control moisture, and be pretty quick and easy.

Or I could do 1 inch XPS, taped, Great Stuffed, etc along with R-13 unfaced FG batts in the stud walls. That should get me R-18 but would be a little more labor intensive.

Either way I'll have a 70 pint/day dehumidifier running to keep humidity 50% or less and the space will be well conditioned. Both options are approximately the same cost.

Seems like option two is the better option as labor is on me.

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Old 02-10-2012, 12:02 AM   #2
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Basement insulation scenarios I'm considering


Screw the FG insulation; worst stuff on the market. If you are taking the time to install 1" of board, why not 2" and be done w/ it? You will likely need to cover the foam w/ fire proofing, and that may be an interior 2x4 wall w/ sheet rock. See local code officials, as foam is not fire proof at all. If you go that route, Roxul, etc, is better than FG, esp below grade. Good work on the rims.

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Old 02-10-2012, 10:21 AM   #3
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Basement insulation scenarios I'm considering


What you are contemplating doing is exactly what I am doing. 1" XPS glued and taped, 2x4 framing with R13 unfaced batts, and possibly adding a dehumidifier if the humidity gets above 50%. I will moniter the humidity next spring/summer when I am done.

Insulation in the rim joists is good for now, but not the best. Either apray foam the required depth or cut and add pieces of XPS in your rim joists and caulk the edges. Here in Minneapolis I am adding 3" of XPS in the rim joists.

B

Last edited by Beepster; 02-10-2012 at 10:24 AM.
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Old 02-10-2012, 11:22 AM   #4
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Basement insulation scenarios I'm considering


Beepster, I'd love to see pictures of the steps you take. I'm doing the same thing, but I'm in the demo phase right now. I was going to do 1 inch XPS foam boards, but double them up to make it 2 inches. At each level, I am going to be taping the seams.
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Old 02-10-2012, 12:58 PM   #5
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Nothing too complicated. Cleaned and scraped the walls. Cut the sheets so they fitted snuggly between the joists and floors. Applied a full tube of ML300 (?) per sheet in a grid pattern. Pressed sheet against wall making sure tongue and groove fit snuggly. Braced overnight. Taped joints with a Tyvek type tape. Caulked along floor.

I am currently framing. Then I have to finish putting pieces in between rim joists. It would be easier to spray in foam with all the "extra" stuff up there, but more $$$. So far I have just used scraps, so nothing out of pocket yet.

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Old 02-10-2012, 03:23 PM   #6
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Quote:
Originally Posted by jklingel View Post
Screw the FG insulation; worst stuff on the market. If you are taking the time to install 1" of board, why not 2" and be done w/ it? You will likely need to cover the foam w/ fire proofing, and that may be an interior 2x4 wall w/ sheet rock. See local code officials, as foam is not fire proof at all. If you go that route, Roxul, etc, is better than FG, esp below grade. Good work on the rims.
That is basicly the jist of my question. Should I just go with 2 inch XPS and be satisfied with R-10 or 1 inch XPS with R-13 for a total of R-18.

It will be a finished space, so 2x4 framing, drywall, etc.
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Old 02-10-2012, 04:04 PM   #7
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Basement insulation scenarios I'm considering


Will it be inspected, and if so, do you need a required R Value? I saw another post here recently where the inspector wanted an R13 when dude only had up 2" XPS (R 10).

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Old 02-10-2012, 04:13 PM   #8
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Basement insulation scenarios I'm considering


Check on the local idiotic and provincial basement insulation requirements to be legal. At least you do not have the magic, imaginary line around your basement at the frost line that is common in some areas and does not make sense.

In my opinion, most basements are over insulated when finished because you lose many of the long term energy benefits of the the thermal stability of the soil and concrete. I reduced the insulation on my basement walls to get the benefit of the thermal stability because my lower level was a conditioned space and that reduced the AC requirements in the summer.

A basement is not like a flimsy stick building above grade.

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Old 02-12-2012, 03:08 PM   #9
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http://www.quadlock.com/technical_li...Insulation.pdf

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Old 02-12-2012, 06:52 PM   #10
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Quote:
Originally Posted by concretemasonry View Post
Check on the local idiotic and provincial basement insulation requirements to be legal. At least you do not have the magic, imaginary line around your basement at the frost line that is common in some areas and does not make sense.

In my opinion, most basements are over insulated when finished because you lose many of the long term energy benefits of the the thermal stability of the soil and concrete. I reduced the insulation on my basement walls to get the benefit of the thermal stability because my lower level was a conditioned space and that reduced the AC requirements in the summer.

A basement is not like a flimsy stick building above grade.

Dick
+1

I wholeheartedly agree here.

I think it is largely overrated as well if a below grade application.
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Old 02-12-2012, 09:14 PM   #11
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Basement insulation scenarios I'm considering


It's not likely that this will get inspected. I take it that R-10 with 2inch XPS will suffice?

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