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Insulation and no vapor barrier questions... help

Posted by dominogold (My Page) on
Sun, Mar 26, 06 at 23:41

I installed R-13 kraft faced batts in my walls without a plastic vapor barrier. So 95% of the walls had the paper barrier but that was it... is this going to be a problem? Haven't basements been installed this way for years and years ? I'm in Michigan and my foundation is only half underground on one side of the house but fully underground on the other side.

Also, my walls vary from 7'5" to 8' high where the insulation sits, then the walls are shimmed to the ceiling which is about 8'4". So I have from 4 to 9" of uninsulated area that will sit between the drop ceiling and the floor joists.... should I go around the room and insulate this outside walls as well or not worry about it.

I just hate working with insulation and hope the answer will be... (don't worry about it because you won't see a difference). :)


Follow-Up Postings:

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RE: Insulation and no vapor barrier questions... help

If you read over the technical resource articles at www.buildingscience.com concerning basement insulation, I think the answer you will find is don't use fiberglass for basement insulation, only use foam. Sorry.


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RE: Insulation and no vapor barrier questions... help

You require vapour barrier on the warm side (in winter) of permeable insulation such as fiberglass. Kraft paper is not a vapour barrier, and even if it was, the batts sit between the studs and therefore the barrier is broken.

What formulaross is saying is fiberglass (and the wood studs) in direct contact with the concrete wall could result in the fiberglass and wood becoming damp and even sopping with moisture and causing rotting and even mold behind the finish wall. Fiberglass is porous to air infiltration, and without the vapour barrier, the warm moist air in the room will migrate to the cold wall surface and moisture will condense.

You want to insulate, and also stop the room air from getting to the wall.

You can accomplish this two ways:

1) by installing extruded polystyrene foam insulation sheets (the blue one) against the wall before building out the stud walls, and then additionally, you could install the fiberglass batts between the studs. This way, the fiberglass and studs are isolated from direct contact with the wall, and you also have insulation. But, you will still have to provide a total vapour barrier on the warm side of this, because any thickness of the polystyrene under 1-1/2" thickness is not considered to be impermeable enough to be considered a vapour barrier. Regarding polyethylene film, if used for vapour barrier on the warm side, the film has to be totally sealed at overlappng joints and at edges of joists and floors.

2) You can install 1-1/2" polystyrene against the wall and build out as above, and if you seal the butting joints and the surrounding edges at joists and floors so you have a total impermeable barrier, ostensibly you do not require another vapour barrier on the warm side. But that may not suit an old school building inspector, if that is applicable for permit.

I believe, without referring to the building science information, this is the concept they recommend.

Ted


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RE: Insulation and no vapor barrier questions... help

Thank you for the info. Unfortunately for me I think it's too late. Guess I'll just have to run the dehumidifier a lot!


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RE: Insulation and no vapor barrier questions... help

"Personally, I would never pull a permit in MY city for finishing a basement. However, I'm different than a lot of folks and read as much as I can about the code and even though I don't pull a permit for basement work I still do it to code as much as possible."

Domino, this is your quote from a concurrent Permit pulling thread on this site. In reading your issue, don't you see the hypocrisy in your position on pulling permits? You feel they are a burden, yet you are constructing a finished basement that may turn into a festering mold nightmare for some future owner of your property. This type of behaviour is exactly why a permit should be pulled, and an inspection granted.


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RE: Insulation and no vapor barrier questions... help

dominogold,

Are the walls finished now? If they are finished with panelling, it's not a big job to remove and replace it. I've done it several times myself. If it's drywalled, I can see your reluctance.

I definitely recommend you at least put vapour barrier over the batt insulation. That is not a major job and is not expensive, and if you do a careful job of using sealant to seal the lapping edges and at the contacts with joists and floor, you should keep the interior air from getting through to the cold wall.

Also, the area at the top should be insulated and more importantly sealed. This is the critical area, because the joist ends and rims are subject to the most air leakage and also need the insulation. You can understand why, when you see all the joist ends and rim joists sit on wood plates which sit on top of the wall at all floors. All the interfaces between the plates and the top of wall, and the joists with the plates and the subfloors are all heavy leakage areas. You may notice there are serious drafts through this area, and at the baseboard area and the whole floor (above)is cold. The cold migrates easily into the joist spaces well into the rest of the house. These areas are also difficult to seal, because of the many intersecting planes of the joist ends, plates and underside of floors. You could cut styrofoam to fit and seal it to the other surfaces. Some people try to resolve this using a simple if not as good a solution of stuffing and sealing bubble wrap into the cavity. One excellent way is to use spray foam insulation in the cavity, which will bridge all the leakage points. Once these areas are sealed you should pack insulation at least to the same extent as the rest of the wall and vapour barrier over.

Regarding installing the styrofoam against the wall to provide separation from the wood studs and fiberglass, I learned this the hard way, as I insulated, vapour barriered and panelled my basement walls at a previous house the traditional way. I did it the way they recommended back then, and thought I did a great job. To make a long story short, I ended up with sopping wet studs, fiberglass and panelling. The wood and panelling was rotting and there was a lot of mold starting to get very thick. What drew my attention that there was something amiss was hearing some grinding sounds coming from the wall. I pulled the panelling off and there were carpenter ants gnawing away on the rotting and wet wood. I found out ants and termites are attracted to and thrive in that environment.

I hope everything goes well for you.

Ted


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RE: Insulation and no vapor barrier questions... help

"Domino, this is your quote from a concurrent Permit pulling thread on this site. In reading your issue, don't you see the hypocrisy in your position on pulling permits? You feel they are a burden, yet you are constructing a finished basement that may turn into a festering mold nightmare for some future owner of your property. This type of behaviour is exactly why a permit should be pulled, and an inspection granted. "

I can see your angle on this, but I don't really see the logic in this case.

First of all, plastic vapor barriers are not a code requirement in my area. Second, there is a lot of controversy on whether vapor barriers actually do more harm than good. You can google this and you find more information contradicting the use of vapor barriers as a benefit as you do positive info. Third, people have been finishing basements without a plastic vapor barrier for decades without issues from the lack of a vapor barrier.


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RE: Insulation and no vapor barrier questions... help

naturelle, thanks for the info. Yes it's already all drywalled. None of my neighbors put up a vapor barrier other than the faced batts so I didn't either...plus it's not a code requirement here.

I think I will put some insulation along the top, can definitely see your point about the cold air inbetween floors causing cold floors above.

What a pain I thought I was done with the insulation hate that stuff...


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RE: Insulation and no vapor barrier questions... help

Domino. I apologize for the tone of my earlier post.


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RE: Insulation and no vapor barrier questions... help

Oh, not necessary really but thanks.

Look if I wasn't already paying $8000-9000 in taxes, I would would pull a permit. But there's just no way when my house was built a year ago with dozens of code violiations that "made it past their inspectors" that I'm going to pull a permit just so an incompetent inspector can give me a hard time for no reason and raise my taxes even further.


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