# 2x6 insulation in 2x4 framing



## Bondo (Dec 8, 2007)

Ayuh,... It kinda defeats the purpose of 6" insulation to Pack it into 4"...
It's the loft of it that does the work, not so much the glass...


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## Daniel Holzman (Mar 10, 2009)

The point about the loft is exactly correct, the glass has almost nothing to do with the insulating power other than to trap air. However, there is probably little difference in insulating value between compressed 6 inch thick fiberglass and uncompressed 4 inch fiberglass batts, so go ahead and use it, you already have it, and relax about the marginal loss in efficiency.


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## Scuba_Dave (Jan 16, 2009)

Yeah, R19 will give you R13 in a 2x4 wall
Sometimes its hard to stuff into a 2x4 wall

and the fiberglass insulation should not be against the cement
Building the 2x4 wall out 6 1/2" to the face of the 2x will give you the clearance you need


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## Kyle Keever (Nov 24, 2009)

*2x6 insulation in 2x4*

Yes you can build the stud wall out to accommodate the 2x6 insulation. You may want to put some thoroseal or similar coating on the concrete for moisture protection. You will likely also need to install a vertical draft stop every 10 horizontal ft for fire code. This can be plywood or drywall. This is just to close the gap behind the stud wall to the concrete to prevent fire from migrating horizontally.


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## hebrewdiver (May 1, 2009)

Scuba_Dave said:


> Yeah, R19 will give you R13 in a 2x4 wall
> Sometimes its hard to stuff into a 2x4 wall
> 
> and the fiberglass insulation should not be against the cement
> Building the 2x4 wall out 6 1/2" to the face of the 2x will give you the clearance you need


Thanks this is great help....I have a load of r19 that was given to me and I have 2x4 framing...glad to know I don't have to go out and buy r13....thank alot for the info


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## concretemasonry (Oct 10, 2006)

Those figures are provided by the pink panther and are probably for the lab tested ideal apllication for R-value of the compressed insulation and do not account for the heat loss through the studs, that can be significant, especially if you happen to use steel studs. (up to 40% loss for the wall compared to the R-value of the insulation R-value itself).

Keep in mind the results are "pink" for new. clean, dry insulation in short term lab tests and not real life. Fiberglass does not really absorb any real moisture, but it and an dust will hold it and only 1% moisture can dramatically reduce the insulation value of the insulation itself. Once fiberglass holds moisture (from condensation, leakage or whatever), the insulating value does not return. Since it has the moisture, the insulation is reduced and this can lead to more condensation/moisture since no wall have a real vapor barrier, but is only a vapor retarder.

You can get away with cramming the 6" batts into the 4"(-) cavity, but you will not get any better real effective insulation, but basements do not really need nearly as much wall insulation as above grade wall. Any soil or basement wall long-term temperature is rarely below 55F, while it may be -30F outside above grade. If you think about it, your floor probably has more area at a temperature about the same as the lower half of the uninsulated wall, so that can often be a bigger comfort problem.

Dick


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## Gary in WA (Mar 11, 2009)

Here is what the panther doesn't tell you: http://www.anchorinsulation.com/pdfs/the economic thickness of thermal insulation.pdf


And about the loss through the studs in the whole wall assembly: http://www.coloradoenergy.org/procorner/stuff/r-values.htm
2x6 vs. 2x4 stud wall: http://www.advancedenergy.org/buildings/knowledge_library/framing/2x4_or_2x6.html


You really should use some rigid foam board to stop any moisture from molding behind your batts: http://www.buildingscience.com/docu...rol-for-new-residential-buildings?full_view=1

You may need a vapor barrier if in a cold climate.
Here is along the line Dick said:
http://www.quadlock.com/technical_library/bulletins/R-ETRO_Value_of_Basement_Insulation.pdf

And don't forget the rim joists: http://www.rd.com/57548/article57548.html
Be safe, Gary


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## High Gear (Nov 30, 2009)

I'd see if you could take the insulation back and apply the money to the methods that GBR has posted.

I'm using these methods on my basement project.


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## Paulie (Nov 26, 2009)

High Gear said:


> I'd see if you could take the insulation back and apply the money to the methods that GBR has posted.
> 
> I'm using these methods on my basement project.


Craigs List?


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## Ted White (Jun 23, 2009)

Excellent thread! Previous comments are right on the money when describing the "loft" of the insulation. Too often compressed insulation in a cavity is equated to better sound isolation. This isn't the case.


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