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Basement blanket insulation, to remove or not to remove?

Basement blanket insulation, to remove or not to remove?

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  #1  
Old 04-13-08, 08:20 PM
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Basement blanket insulation, to remove or not to remove?

House is about 4 years old, ready to start working on finishing the basement. Builder put up plastic covered blanket insulation on furring strips all around the outside walls, question is do I need to remove all of it before I can start framing? Basement is around 2100sq, so we are talking about ALOT of insulation, which I would hate to waste, but I also don't want to do anything that is going to cause problems in the future. Any opinions would be helpful.
 
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  #2  
Old 04-13-08, 08:54 PM
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I believe some of these questions were answered in an earlier post but fya go to the DOE website and read up on basement insulation, the bottom line is that basements should only be insulated on the outside unless the insulation space is very well vented due to the build up of moisture comeing thru the concrete wall. if you have to insulate on the inside you should use only insulation that will not support mold. Like esp or spray foam. and even then your wood studs will likely mold in time.
O'tools comentary on Murphy's law (Murphy was an optimist)
 
  #3  
Old 04-14-08, 10:40 AM
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The first thing I tried was read the sticky at the top of the forum that was posted to the DOE website on insulating foundations, but it results in a document not found error. I also looked around for other posts on this subject, but did not find anything that I understood as a answer to my specific question.

Just so I'm clear, when you say "outside", do you actually mean inside the concrete wall, but outside where the framing would go? My questions are only related to the insulation on the interior wall of the concrete foundation.

Seems like some builders frequently use the blanket insulation technique to give unfinished basements some form of barrier, which I do appreciate, but should I first remove it before attempting to frame out the basement? It seems like such a waste to do so, but if it's going to cause potential problems if I don't, that would be helpful to know ahead of time.

Thanks for the response.
 
  #4  
Old 04-14-08, 11:54 AM
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I had the same thing in my basement. I talked with the chief building inspector and he said that there was no need to remove the insulation before framing the foundation wall. I essenailly trapped the insulation between the new framing and the foundation wall... leaving about a 1 inch gap between the studs and the foundation wall. It actually worked out well... since the inspector said I didn't have to fire block since the insulation blocked all gaps against the foundation wall.

I'm not sure about the other fellas comment about mold build up.

Would mold build up on fiberglass insulation?
And if the blanket insulation has a plastic sheeting is there still a concern that the studs themselve would mold?

If there is a concern for molding... what;s the recommendation? Remove existing insulation... put barrier against foundation wall... frame and then re-insulate?
 
  #5  
Old 04-14-08, 05:38 PM
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This section from Building Science explains the latest thinking in basement insulation...long read, but really good info:

http://www.buildingscience.com/docum...t%20insulation
 
  #6  
Old 04-14-08, 08:57 PM
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Thank you for posting, I looked through the article, but I'm going to need it put in to more simpler terms. How does it relate to my question exactly? The article seemed to have mostly negitive comments regarding interior insulating.
 
  #7  
Old 04-15-08, 01:36 AM
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Good morning,

I guess I could have just copied this part for you:

If basement wall systems are designed and constructed to dry to the interior regardless of where insulation layers are located interior vapor barriers must be avoided. This precludes interior polyethylene vapor barriers installed over interior frame wall assemblies or any impermeable interior wall finish such as vinyl wall coverings or oil/alkyd/epoxy paint systems.

If an interior insulation layer is used the indoor air should be prevented from reaching the concrete structural wall assembly or rim joist assembly (unless insulated on the exterior) in any significant volume. Rigid foam systems or spray-applied foams are recommended for this purpose, because they allow drying, are not sensitive to moisture damage, and do not support mold growth essential characteristics for all materials which contact the basement wall and basement floor slab.

I know- it IS a long article
 
  #8  
Old 04-16-08, 02:04 PM
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So does the first paragraph mean you don't want a interior vapor barrier that sits right on top of the concrete? This is fine for me because there are furring strips, insulation and then the white plastic. Correct?

I'm not sure I understand the second paragraph at all.

Am I just that clueless, or am I maybe asking the wrong question, I guess I thought the answer would be a simple one.
 
  #9  
Old 04-16-08, 02:55 PM
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suggestion

I guess if moisture is an issue, you could remove the insulation the builder installed, save it, apply eps board to the foundation walls, frame out your stud wall, then re-use the batt insulation in the wall cavity.

I'm still trying to decide myself if the eps board is definitely the way to go or not, but if you do go that route, that's one way to not let the 'free' insulation go to waste. You might poke big holes in the vapor barrier so the drywall can breathe, though (the suggestion seems to be unfaced batt when you go this route, because the eps board acts as a vapor barrier, and you don't want to trap moisture in the wall cavity)

Also, I think the new location for the sticky to basement insulation is here (maybe someone could update that): http://www.eere.energy.gov/consumer/.../mytopic=11470
 
  #10  
Old 04-16-08, 05:01 PM
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This is the way I understand it...

Remove the blanket insulation. use styrofoam or sprayed in foam between the studs.

If you have inside drainage, like sump pump, there will be more moisture to contend with than if you have exterior preventative measures.Build your stud walls away from the block- leaving the gap between the walls and the block allows for air circulation. Radiant floor heat will do much to add to the comfort level of the room.

It all gets kind of confusing to me from that point on. Here's a page from another forum with much discussion of methods.http://boards.hgtvpro.com/eve/forums...1/m/3921031062

I know I have working perimeter drainage around the exterior foundation. I have well sealed exterior walls. I have clean gutters with downspouts that extend 10 feet away from the house. The land is graded to slope away from the house. I do not have any shrubs or trees growing close enough to the foundation that the roots may breach the block. I have no overhanging trees to clog the gutters.

I run a dehumidifier year round because I have an indoor hot tub. My house is actually a split level, so is more open to the conditioned air than a house with a full basement. If I were adapting a basement to living space, I would want better access to the upstairs than just a basement door- maybe open one of the stairwell walls, again to be more exposed to the conditioned air.

For years, we all used fiberglass batts with a vapor barrier...I assume that is still permissible if all other conditions are met.

If someone out there has a different or better interpretation of this, please chime in. Let's see if we can get the best new information into a sticky, combined with the new link woops provided. We need one viewpoint that reflects the new recommendations, so we all give the same reply.

Connie
 
  #11  
Old 04-18-08, 11:49 AM
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I don't want to waste, but I also don't want to do alll the additional work involved in removing the diaper, cutting it into strips, and putting it back in to the wall. If I were to consider doing that, would I also need to remove the furring strips? I keep hearing that wood should not be in direct contact with the foundation, but that is currently the case, is that part of the reason why the diaper should be removed? Where if any, would I put a plastic barrier in that situation?

Also, I will be using steel studs to frame the basement, not wood.
 
  #12  
Old 04-18-08, 05:11 PM
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Oh, that's great that you're using metal stud...definitely the best option.

If you check the sticky at the top of the page, you'll find all new links and updates. Thanks to woops for the suggestion!
 
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