# Insulating & Vapor Barrier Basement



## itsnotrequired (Apr 30, 2010)

do you have a link to the foam you are thinking of using? not all are created equal. you will want to use a closed-cell xps foam. check out the following link for more info.

http://www.buildingscience.com/doctypes/enclosures-that-work/high-r-value-foundation-assemblies

xps is nice because it provides insulation as well as vapor retardation. thickness will depend on how much r-value you want. the fiberglass batts provide additional insulation level. you can skip it if you are in a warmer climate.


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## thetroups (Apr 30, 2012)

something like...
http://www.lowes.com/pd_41503-46086-RPP-12-S8+%284X8%29_4294858106+5003695+5003697+5003696_4294937087_?productId=3362406&Ns=p_product_prd_lis_ord_nbr|0||p_product_quantity_sold|1&pl=1&currentURL=%2Fpl_10%2B15_4294858106%2B5003695%2B5003697%2B5003696_4294937087_%3FNs%3Dp_product_prd_lis_ord_nbr|0||p_product_quantity_sold|1&facetInfo=$5%20-%20$10|$15%20-%20$25|$10%20-$15

If I am wrong please direct me to the proper product.


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## itsnotrequired (Apr 30, 2010)

you'll want this stuff

http://www.lowes.com/pd_337591-210-M48150LOWES_4294858110_4294937087_?productId=3308686&Ns=p_product_qty_sales_dollar|1&pl=1¤tURL=%2Fpl_Foam%2BInsulation_4294858110_4294937087_%3FNs%3Dp_product_qty_sales_dollar|1&facetInfo=

you'll want extruded, not expanded polystyrene


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## Gary in WA (Mar 11, 2009)

Either f.b. will work, just need it thicker if ESP.

Where are you located?

Gary


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## thetroups (Apr 30, 2012)

Located in York, PA it gets cold here in the winter and humid in the summer.


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## thetroups (Apr 30, 2012)

That stuff is not cheap that is for sure... to do all the walls and floor that would be a large investment on just foam.


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## itsnotrequired (Apr 30, 2010)

GBR in WA said:


> Either f.b. will work, just need it thicker if ESP.
> 
> Where are you located?
> 
> Gary


i thought xps was the preferred choice for interior basement panel insulation, since eps is more permiable and doesn't create as good a vapor retarder when compared to xps. or is the solution to use thicker eps to get effective vapor protection?


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## Windows on Wash (Aug 30, 2011)

itsnotrequired said:


> i thought xps was the preferred choice for interior basement panel insulation, since eps is more permiable and doesn't create as good a vapor retarder when compared to xps. or is the solution to use thicker eps to get effective vapor protection?


Vapor permanence is not as important as air tightness at the end of the day.

Bulk air transfer will carry far more water (about 100X) as diffusion.


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## Gary in WA (Mar 11, 2009)

Page 33, 57-61: http://www.buildingscience.com/docu...merica-high-r-foundations-case-study-analysis

Figs. 13, 14: http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems

As WoW said correctly, it's the air gap that will get you: http://www.carb-swa.com/articles/in%20the%20news/HomeEnergy_The%20Challenges%20of%20Basement%20Insulation.pdf
I forget some of the info in my links occasionally too, LOL.

Compare your HHD with these Cities for the foam thickness: http://www.buildingfoundation.umn.edu/FinalReportWWW/Chapter-5/5-optimum-main.htm

Or find the dew-point, let me know...

Gary


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## itsnotrequired (Apr 30, 2010)

so what is the preference of xps over eps? looks like xps gets you more r-value per inch and isn't as fragile as eps. i plan on finishing my basement with xps but was curious what other opinions are.


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## mikegp (Jul 17, 2011)

Use 2 inch XPS if you want decent insulation and vapor barrier properties. I don't suggest using fiberglass insulation in basements. If it gets wet it becomes pretty useless and it also can mold. There are nice alternatives like Roxul.


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