# Basement Insulation Question ?



## Windows on Wash (Aug 30, 2011)

There are no conflicting thoughts on this matter.

Foam board is more expensive but the preferred way to properly insulated your basement walls in conjunction with interstitial wall insulation.


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## Jim Ignatowski (Dec 20, 2011)

I appreciate the response. I do have room for both. I'd prefer not to screw into my foundation walls, can you recommend an adhesive for mounting the foam board? Thx


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## Windows on Wash (Aug 30, 2011)

There are foam specific glues and they are widely available at your normal hardware outlets. 

Start gluing and insulating.


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## Dave Sal (Dec 20, 2012)

http://www.loctiteproducts.com/p/pl_ca_300_voc/overview/Loctite-PL-300-VOC-Foamboard-Adhesive.htm


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## Jim Ignatowski (Dec 20, 2011)

Thanks Everyone! Appreciate it


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## ThatDaveGuy (Dec 31, 2010)

Windows on Wash said:


> There are no conflicting thoughts on this matter.
> 
> Foam board is more expensive but the preferred way to properly insulated your basement walls in conjunction with interstitial wall insulation.


You're right, there may not be conflicting thoughts on it but it can be difficult for us noobs to sort through all the science involved and make sense of it. People want to just throw FG in and call it good when the reality is that differing types of insulation function differently, and when you factor in the various aspects of conduction/convection/radiation spiced with a dash of thermal bridging it can be a tad daunting.

The input from all the mavens here is greatly appreciated :thumbsup:


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## Jim Ignatowski (Dec 20, 2011)

I have a follow-up question on this if someone has the time. If the foam board is not continuous because of obstructions, will that nullify the effect? Meaning if I can only cover 3/4 of the foundation wall with foam board, will that still help or make things worse? 

This is an old house where everything was originally mounted on the concrete walls, electrical receptacles were embedded, etc... Thanks


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## Gary in WA (Mar 11, 2009)

The amount of wall you cover is saving the most on your heating bill; http://www.quadlock.com/technical_library/bulletins/R-ETRO_Value_of_Basement_Insulation.pdf

Which Zone are you located in?; http://energycode.pnl.gov/EnergyCodeReqs/index.jsp?state=New York

Gary


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## Jim Ignatowski (Dec 20, 2011)

Great info ... Thanks Gary! I'm located in Zone 4


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## Windows on Wash (Aug 30, 2011)

ThatDaveGuy said:


> You're right, there may not be conflicting thoughts on it but it can be difficult for us noobs to sort through all the science involved and make sense of it. People want to just throw FG in and call it good when the reality is that differing types of insulation function differently, and when you factor in the various aspects of conduction/convection/radiation spiced with a dash of thermal bridging it can be a tad daunting.
> 
> The input from all the mavens here is greatly appreciated :thumbsup:


Dave,

I do not doubt that the information is tough to sort through and I assure that it is difficult for the pros to keep up the science and ever evolving technology.

I promise you that if you asked 10 contractors the same question on insulation, you would get 10 different answers and probably 8 or better would be wrong by current building science standards. 

Keep on researching and you will find out what is right for your application, home, and climate. 

Guys like Gary, jklingel, Tom Struble, Joecaption, etc., provide a wealth of both technical and application information. Pick through their posts and you are getting the benefit of over a hundred years of experience.


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## Gary in WA (Mar 11, 2009)

For your location, R-10 foam board or R-13 cavity fill is required. If you check locally you should be able to mix-n-match to get total R-value. If not, show the inspector this, pp. 11 or 12, *footnote "c" *for "basement insulation"; http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&ved=0CDoQFjAF&url=http%3A%2F%2Fwww.resnet.us%2Fuploads%2Fdocuments%2Fconference%2F2012%2Fpdfs%2FBarcik-Energy_Code-IECC2012_vs_2009IECC.pdf&ei=eWHoUsz6AsLboATD84GgCw&usg=AFQjCNF3dEueP0VMXraPlA9K_FKuiqke2Q&bvm=bv.60157871,d.cGU&cad=rja

Keep in mind the more cavity fill fibrous you add; the weaker it makes the foam board against condensation; the colder the inside face of FB. R-10 FB and no cavity fill is fine and optimum, the cavity moisture will be controlled by the HVAC as the studs/insulation is in the conditioned space; http://www2.dupont.com/Tyvek_Weathe...rior Insulation Building Science Bulletin.pdf

Option 2; less amount of FB, with some cavity insulation; need closest large city to figure local dew-points based on foam thickness....

Option 3; wood frame wall with cavity insulation only. If choosing this, I can explain it better.

Gary
PS. Dave, add WoW to that list! Thanks!


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## ThatDaveGuy (Dec 31, 2010)

I have nothing but praise for this site, the people here sharing their expertise so willingly have taught me a great deal and saved me a lot of time and effort. Just reading through threads that have no bearing whatsoever on my projects has taught me a lot in details or materials or sometimes just looking at a problem differently.

Maybe the single most important thing I have gotten from reading here is the realization that there is no ONE answer to any of it, assessing and diagnosing my particular situation is the hardest part but the one that determines the outcome. Having this kind of access to pros that know is one of my most valuable tools.


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## Windows on Wash (Aug 30, 2011)

Roger that.

That is why we ask folks so many time to post up where the home is, what their home construction is, picture, etc.

Keep researching and know that you are miles ahead of 99% of your other homeowners in your knowledge base and thoughtful approach.


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## Gary in WA (Mar 11, 2009)

Any other questions, Jim?

Gary


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## Jim Ignatowski (Dec 20, 2011)

I don't think so Gary ... I greatly appreciate you taking the time to provide this information. I was going to post a few pictures of the foundation walls and the wood framing, but I don't think the pictures add much value. 

Since I'm planning on using the existing framing, the amount and type of insulation will vary in different areas of the basement. In some areas the wood frame is nailed directly to the foundation wall and there is a 1" cavity between that wood to add foam board. In other areas there is a wood frame 6" from the wall which could support both foam board and fibrous insulation, but as you indicated above, this reduces the effectiveness of the foam board. There are some other scenarios down there too, but ultimately I think every wall should be able to get foam board coverage. I'll have to read up on combining fibrous w/FB. 

Thanks again!


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## Gary in WA (Mar 11, 2009)

Even 1" XPS unfaced is better than just cavity fill. Piece-meal it in if needed, canned foam between the joints and under perimeter; it requires completely air-tight installation. Taping the joints will work short term but as the fb ages, it shrinks- breaking the bond between the two pieces; allowing air entry for condensation on cold concrete wall. Even the adhesive should be applied in 1' square grid patterns to limit air movement if compromised by any 1/16" gaps anywhere; http://joneakes.com/jons-fixit-database/743 Where the frame wall is close to concrete, even 1/2"XPS, then add XPS between the studs- then compress cavity fill to meet minimum thickness is fine.http://numsum.com/spreadsheet/show/21111

Canned foam/XPS the rims, after caulking the joints touching the rim joist; to sheathing/decking above, to mudsill plate. Any cavity between colder concrete wall/fibrous insulation will allow/have convective loops; robbing you of R-value and creating a chase open for fire travel behind the wall. An outlet fire could easily run horizontally to travel vertically up the wall and into a floor joist cavity, across that to and up a plumbing chase/space around pipe; to the attic (air seal all top plate penetrations) and catch the roof framing on fire--- burning the house both down/up at the same time. http://publicecodes.cyberregs.com/icod/irc/2006f2/icod_irc_2006f2_6_sec002_par017.htm

http://www.buildingscience.com/documents/published-articles/pa-foam-shrinks

My point was; use code required R-value fibrous insulation to meet code after FB insulation used, don't add more than required cavity fill to lower dew-point at foam. Fig. 3-6; adding cavity fill R-value reduces FB dew-point temps; http://www.buildingscience.com/docu...ld-weather-condensation-using-insulation/view
Check with your local AHJ. 

Gary


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## Jim Ignatowski (Dec 20, 2011)

I'm sure I'm not the only one who appreciates the level of detail you're providing. This is great info. 

From what I can see, the highest R-Value FB insulation is about R5 ... Does that sound right? In areas where I have a large cavity I will use both, but there are areas of the basement where I will not be able to achieve the R-value without adding some wood framing for fibrous insulation. In those areas I was planning on using the highest R-Value FB that will fit between the 1" framing that's on the concrete.


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## Gary in WA (Mar 11, 2009)

PIC is R-6.5 (aged) though the air sealing of it requires impeccable. http://www.buildingscience.com/docu...ns?topic=resources/vapor_barrier_code_changes

The framing is usually for the required wiring. You could also cut FB for between the studs, just be sure it is glued to the FB on the concrete wall. PIC (foil-faced polyiso) or PIR;http://www.buildingscience.com/documents/information-sheets/building-materials-property-table/

Gary


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## Gary Evans (Jan 27, 2014)

Lots of very good info here and I'm putting my two bits in too.

Very first thing, make sure you have a dry basement........everyone here knows this anyways.

Best and most expensive way......spray foam applied between the studs, just like you see on Holmes on Homes and a few other shows.

Second best and second most expensive way........Styrofoam SM installed between the studs. Gaps around boxes and along the framing need to be sealed with cans of XPS non-expanding foam.
Windows...... you mentioned using a Styrofoam glue for attaching the panels to the concrete.......there is a better way, use plastic anchors and a hammer drill. 


The cheapest and most common way.......and the one that causes the most confusion.
- fiberglass insulation.
The problem with fiberglass is it likes to soak up water so don't use this if you think there's the potential of a wet or damp basement.
There's been lot's of people do this a lot of different ways and it has evolved several times.

I think the best way is...... first make sure your wall studs are about 1" or more from the concrete wall and the bottom plate is sitting on sill gasket.........you should do this no matter which insulating method you use.
If your using fiberglass insulation you want ventilation between the insulation and the concrete wall anyways.

Next you should make sure the fiberglass bats can not come in contact with the concrete, best way to do this is apply exterior building wrap like Typar on the back side of the stud wall........this allows the insulation to breath and stay dry.
The vapor barrier then goes on the front side (warm side) of the wall and insulation.


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## mcu (Mar 2, 2008)

Sorry...don't mean to kill your post here but I recently bought a house and the basement is insulated the way Gary just described as the most common way. 

Here is my post http://www.diychatroom.com/f103/renovating-basement-insulation-gut-job-keeper-195298/#post1300353 . 
I would love if you guys commented and Gary since you describe the common way to insulate, tell me if it's a keeper or not.

Thanks


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## Gary Evans (Jan 27, 2014)

Yes, I'll stick my neck out here and say that doing it the way I described is a keeper.

It's not the very best way but the most practical way if your on a budget......and better than at least 3/4 of the homes out there.


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