Basement wall is wet/icy

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  #1  
Old 01-13-13, 04:00 PM
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Basement wall is wet/icy

I am in the process of finishing the basement on our new (built in 2012) home. While putting in wall boxes for lights tonight, I found that one wall was wet behind the insulation. I pulled it down, and it is frosty/wet/icy all along that wall. This was insulated by the builder, and vapor barrier was installed. The vapor was not well sealed when we moved in, and since the walls weren't finished yet, I found no rush to properly seal it. I have also had to cut the vapor to install outlet and light boxes all around the room, those cuts have not yet been sealed either.

looking for advice on how to proceed, what might be causing the one wall to be cold but not the adjacent wall. I have contacted the builder to remedy the situation, but I fully expect a run-around, and would like to be better informed when I talk to them.


oh, I live in North Dakota, so the winters can be harsh, weather lately has been fluctuating up to 30's last week, and down below zero over the weekend.

Thanks.
 
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Old 01-13-13, 04:07 PM
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So are you saying that when you cut the hole that you found that it was icy back there?

Or that you cut a bunch of holes in the vapor barrier/insulation... that they were open that way for a few days or weeks, and that NOW it's icy back there?

If you removed an air barrier that has allowed warm moist air from the basement to come into contact with the wall, that's why you suddenly have ice there.
 
  #3  
Old 01-13-13, 04:10 PM
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The vapor had been cut for awhile, as I finished running electrical. So, I caused this? (Wouldn't be the first time I've done something dumb)
 
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Old 01-13-13, 04:15 PM
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Well if it wasn't icy when you first looked behind there, I think the answer is yes. If there was no ice back there originally (when you first opened it up) the builder probably did a fine job of air sealing the wall, keeping the warm, moist interior air from coming into contact with your cold wall.

Now that you've punctured the envelope, warm air is getting back there where it can condense. The best thing to do probably would have been to leave the air barrier/vapor barrier of the original walls intact, frame a new wall in front of it, and run the electrical in that.
 
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Old 01-13-13, 04:17 PM
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When I opened it, it wasn't this cold yet. Either way, do I tear it down now, let it dry then reinstate and revapor?

and if I cut the vapor all around, any idea why just one wall would have it?
 
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Old 01-13-13, 04:33 PM
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Is this wall above or below grade. Uncommon for a wall below grade to be that cold.
 
  #7  
Old 01-13-13, 04:36 PM
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Below. The ice is moving from the top down. We moved in late last summer and haven't had he final grade done on the yard, so the dirt may not be piled up as high as it should be on the outside.
 
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Old 01-13-13, 04:36 PM
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Which wall is it? North? Does this wall have any penetrations on the outside? Electrical box or water or gas?

Most of the time frost like that will occur on the coldest wall (like the north facing slope of an attic roof) or on the side of the house that has negative air pressure (due to air leaks at penetrations, sill plates or other leaky locations). Sometimes it is simply the wall opposite the prevailing wind, since the wind creates air pressure on one wall (pushing in) while your warm humid conditioned air is finding its way out (the same amount of air that leaks INTO a house is also leaking OUT.

So since it's winter, I think you are kind of in a pickle... at a point at which you can't really go any further as far as sealing it up is concerned until it warms up and the wall has a chance to dry out. Seal it up now and you just trap the moisture back there, which would be a bad idea, IMO.

We have some other members here who are probably better suited at this sort of question, so if you check back later I'm sure others will chime in. Anytime you talk about a vapor barrier on a basement wall it's kind of a slippery slope because with various climates and techniques, you have a lot of variables that can lead to potential problems.

IMO, once the wall dries out, if you can air seal the wall back to its original air tight condition you would probably be okay.
 
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Old 01-13-13, 04:42 PM
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It is north wall, primarily north/northwest wind here, especially in the winter. The more I read your responses and think about it, a number of factors may be playing against me. We have been unusually dry here over the last two years, and the ground is receding away from foundations. And the fact hat I started this project in October and have been taking my time, the vapor has been cut for over 2 months.

If I open up my heat vents down there and run fans on that wall, any thoughts on if hat would help?

the common practice for insulating basements around here is insulation against the concrete, then vapor.
 
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Old 01-13-13, 05:13 PM
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.


Agreed.......there are likely several factors at play here.

The vapor barrier needs to be continuous and all gaps or openings need to be sealed.....and there needs to be sufficient insulation. Sometimes......builders can be sloppy.....so you need to really look at the overall job and assess what corrections are required.....and it may make more sense to start fresh. When you say that the walls were insulated with vapor barrier applied.....does this mean the walls are studded already? If the insulation is just attached with vapor barrier directly to the concrete....then you will need to remove it if you build studded walls.....and place a new continuous vapor barrier on the warm side of the new wall after you fully insulate it. The builder installed insulation will likely be minimum code at best. You could also consider closed cell spray foam applied directly onto the concrete which would form a continuous seal and thermal break.....then no vapor barrier is required and all the sealing headaches that go with it. This could be done after the studs walls are in place if they are built slightly away from the concrete.

The fact it is a new house also means it is probably still "drying out"......meaning all the structural lumber is contributing to the humidity. What is the humidity level in the basement?

The key......you need to add insulation and stop any moisture from reaching the cold exterior walls......and make sure the humidity level itself is not too high.


.
 

Last edited by Halton; 01-13-13 at 05:34 PM.
  #11  
Old 01-13-13, 06:12 PM
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While putting in wall boxes for lights tonight, I found that one wall was wet behind the insulation. I pulled it down, and it is frosty/wet/icy all along that wall. This was insulated by the builder, and vapor barrier was installed. The vapor was not well sealed when we moved in, and since the walls weren't finished yet, I found no rush to properly seal it. I have also had to cut the vapor to install outlet and light boxes all around the room, those cuts have not yet been sealed either.

looking for advice on how to proceed, what might be causing the one wall to be cold but not the adjacent wall.

I caused this? (Wouldn't be the first time I've done something dumb)
I'm not at all sure that you caused this. Given that it's only on one wall and that you've been working on all of the walls, I would suspect the lack of final grading and the northern exposure have more to do with it than your cutting the vapor barrier.

I would continue with the electrical work and wait for spring and the final grading. Then I would check for, and eliminate, any moisture infiltration, and fully air-seal the walls before hanging the sheetrock or other interior finish. IMO.
 
  #12  
Old 01-13-13, 06:50 PM
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Here's some reading for you:
BSD-103: Understanding Basements — Building Science Information
Note Photo #2 the fiberglass covered with a VB and drywall. Concrete walls exposed to moist soil will pass that moisture through to the inside (the tar doesn't stop it) and it needs to be able to evaporate to the inside. This is the next problem your basement will face if you finish as currently outlined.

Currently you are seeing the moisture from the inside, which should have been a known issue to your builder and thus he should never have left it unfinished knowing this would happen. Actually he should never have used the fiberglass in the first place, see Photo #4.

I'll let you read and follow the links at the bottom as there are many articles on basements.

Bud
 
  #13  
Old 01-13-13, 07:04 PM
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jn115,

maybe you could actually clarify the makeup of your basement walls. I don't see where you specifically mention studs... or fiberglass. It seems everyone is assuming that when you say "insulation" you are referring to the common type of fiberglass batts (3 1/2" or 5 1/2") installed in a 2x4 framed wall and a separate clear poly vapor barrier applied to the interior of that wall.

Do you have thermal blanket insulation, as pictured in "photo3" of the document that Bud linked to? And since your foundation isn't backfilled yet, can you tell whether the exterior side of your foundation has a drainage membrane or any other type of waterproofing applied to the exterior? That would affect whether or not thermal blanket insulation (aka "the diaper"... LOL) could be problematic.
 
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