2x4 or 2x6 insulation when in front of pipes.

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Old 12-12-17, 11:56 AM
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2x4 or 2x6 insulation when in front of pipes.

I'm getting closer to insulating my basement walls as part of my finishing project, and have a question on what to do with one wall.

I already installed rigid foam to the basement walls, and then have 2x4 walls built in front of them. PT base plate as well, fireblocking done, and should meet code when I call the inspector.

But on one wall, the actual wall was built about 4 inches off the wall in front of the drainage piping. So for this wall, would you still use 2x4 batts or perhaps 2x6 batts since their is still another ~3 inches behind those studs?
 
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Old 12-12-17, 11:58 AM
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Whatever you are building the rest of the walls with is what I would use, noting special required!
 
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Old 12-12-17, 01:11 PM
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There is a ratio used for exterior above grade walls that limits the amount of air permeable insulation installed to the inside of your rigid foam. The objective they are hoping for is to be sure the first surface of the rigid remains warm enough to avoid condensation from warm interior air.

The first question is, how thick is your rigid? And then what climate region of NY are you in.

Here is the related link:
Calculating the Minimum Thickness of Rigid Foam Sheathing | GreenBuildingAdvisor.com

Bud
 
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Old 12-12-17, 05:08 PM
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I have no idea what the exterior insulation of the home would be, as I did not have this home built. But do know it was built in the late 1990's.

I am in NY Zone 5 area, upstate NY area. We get cold and snow here. But I am also referring to a below grade Basement with poured concrete walls. Those walls now have 1/2" rigid foam on them, with 2x4 walls built in front of them.

So, 2 walls will get R13 between the studs. But was curious about the other wall that was built 'off the wall' due to the piping running along it. So wasn't sure about still using insulation for 2x4 walls, or maybe insulation for 2x6 walls to fill the cavity better.
 
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Old 12-12-17, 07:44 PM
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The article was about the exterior of a house but in your case we can apply it to those basement walls and you have only 1/2" of rigid. In zone 5, per their chart, you would want r-5 (one inch) for 2x4 walls. You would be stretching it using r-13 so I would not recommend going up to the 6" insulation level.

if the gap is right you might be able to run the insulation horizontally behind the studs and leave the cavity empty.

Or slide in more rigid then use the 6" insulation.

Bud
 
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