# Foam Boad Insulation



## thetroups (Apr 30, 2012)

What is the best foam board insulation to use in the basement to glue right to the block wall? I have been doing a ton of research and I am still not 100% sure on this topic. 

How thick should it be, and what is the best to use for the money? It seems to range from 10-30 per sheet pending on thickness.

Please link me to Lowes or HD product pages when making a recommendation.

Thanks
Matt


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## itsnotrequired (Apr 30, 2010)

i am doing my basement (poured concrete wall) with 2" xps foam board, secured to the wall with pl300 adhesive. done quite a bit of research and this will work best for my application.

http://www.menards.com/main/buildin...50-rigid-foam-insulation/p-1384803-c-5779.htm

http://www.menards.com/main/paint/a...rd-construction-adhesive/p-1504428-c-7921.htm


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## thetroups (Apr 30, 2012)

That is a little out of price range.


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## itsnotrequired (Apr 30, 2010)

i mean, you get what you pay for. thinner foam is certainly cheaper but if the foam is not thick enough, you will not get adequate thermal break and/or an effective vapor retardeder. this can lead to condensation problems. saving a few hundred bucks up front may end up costing you thousands down the road. i'm not trying to scare you, it may not be an issue for you. lots of factors here such as your location, does the basement already have moisture problems, etc. from what i can gather, anything less than 1" of xps isn't adequate.


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## thetroups (Apr 30, 2012)

Ok that is the response I was looking for... I don't mind spending the money if it is worth it and a valued purchase... just don't want to over due or do things that are not "worth" it.


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## itsnotrequired (Apr 30, 2010)

some experts should weigh in on this. lots of information out there, some of it bad. i've used the buildingscience website for most of my info. you should check it out.

expanded polystyrene (eps) is an alternative to xps and is more economical on a per inch thickness basis. note that eps has less insulating quality (i.e. you need thicker eps to get the same r-value as a given thickness of xps) and is a little harder to work with (more prone to damage).


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## concretemasonry (Oct 10, 2006)

itsnot required -

There is a very strong tendancy to over-insulate a basement based on the fictitious R-value and lack of knowledge of the benefits of of thermal storage and moderating effects of the soil. If a basement is a conditioned space, over insulating can actually cost money and reduce comfort in a climate with cold winters and warm, humid summers.

Dick


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## itsnotrequired (Apr 30, 2010)

2" xps is r-10 so i doubt there is an over-insulation issue. i was soliciting feedback more on recommended minimum thickness of foam boards or why one would choose eps over xps.


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## packer_rich (Jan 16, 2011)

*location*

It would be helpful if the OP mentioned where he lives.


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## concretemasonry (Oct 10, 2006)

R-values can be meaningless when it comes to long range economics and thermal heat capacity.

An r-value is best used by a cute pink cat and not an economist or a member of ASHRAE.

Heat/cold flow in either direction and insulation can also prevent some beneficial results that they cute pink/blue cat does not want to recognized since promoting high insulation values where not really needed do not sell or are not cheaply advertised.

Dick


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## itsnotrequired (Apr 30, 2010)

soooo, for those of us that are not economists or members of ashrae, is there any recommendation on minimum thickness to have effective vapor retardation or a reason to select eps over xps?


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## concretemasonry (Oct 10, 2006)

You will just have to follow the requirements of Wisconsin to get a D-, which is a minimal passing grade. Codes are not written for economics or practicality, but for simple enforcement by the typical code enforcer. - It is just the cheapest way to build/be legal and not necessarily the best.


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## M3 Pete (May 10, 2011)

concretemasonry said:


> You will just have to follow the requirements of Wisconsin to get a D-, which is a minimal passing grade. Codes are not written for economics or practicality, but for simple enforcement by the typical code enforcer. - It is just the cheapest way to build/be legal and not necessarily the best.


Let's just say I lived in Minneapolis, and wanted to insulate my basic concrete basement. What would you recommend, if anything?


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