Basement Insulation and Vapor Barrier Questions

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Old 12-20-04, 01:59 PM
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Basement Insulation and Vapor Barrier Questions

I have read through much of the forum and while I have found a lot of helpful information I do have a couple of questions:

I am currently in the process of finishing my basement. Unfortunately, I have had some questions arise that I had not foreseen before starting (I've had differing opinions given). I have framed the entire basement, and have run electrical. I'm now starting on insulation installation. I have purchased R-13 with Kraft facing. I was planning on just using the Kraft facing as my only vapor barrier. I live in Northern Utah and have a very dry basement. The house is almost 4 years old.

1. Does my method seem sound, or should I install another vapor barrier over the Kraft facing? (Note: I really don't want to tear down my framing to install a vapor barrier against the concrete.)

2. Does electrical wiring go in front of or behind the insulation?

3a. I have stuffed R-13 into the areas behind the cross framing that some of the interior walls lead off of. I realize that the compression reduces the effectiveness of the insulation, but something is better than nothing, correct? 3b. Will the fact that the insulation is compressed directly against the concrete wall cause any problems?

Thanks in advance for any help.
 
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Old 12-20-04, 04:35 PM
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Quite often in a basement you are concerned about moisture from the outside. I've seen some pretty heavy snow and rain in the Logan area so I'm sure there is at least some mositure in your soil. I would generally put a plastic vapor barrier against the masonry basement wall since there is usually more moisture on the outside trying to get in.

Generally electrical wires are run through the center of studs so you split the fiberglass batts so the insulation goes on both sides of the wires.
 
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Old 12-20-04, 05:13 PM
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Thanks for responding.

Unfortunately, I've already framed the walls in. I know I messed up, but I'm hoping that someone has a good way to resolve this problem short of tearing the walls back down.
 
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Old 12-21-04, 06:43 AM
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you did not mess up

Actually, you in good shape. Plastic on the wall is a moisture trap. It can also act as a good condensation plane, so unless it drains away from the interior, avoid it like the plague. Did you leave a gap between the masonry wall and the stud wall? If you did, you'll be fine, just make sure fiberglass insulation does not come in contact with concrete. If you haven't run your wires yet, here's a litttle work saving tip: run them behind the stud wall by attaching them with zip-ties. That way you don't have to split the insulation batts to fit them in there.
 
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Old 12-21-04, 08:16 AM
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Originally Posted by markiz37
Actually, you in good shape. Plastic on the wall is a moisture trap. It can also act as a good condensation plane, so unless it drains away from the interior, avoid it like the plague. Did you leave a gap between the masonry wall and the stud wall? If you did, you'll be fine, just make sure fiberglass insulation does not come in contact with concrete. If you haven't run your wires yet, here's a litttle work saving tip: run them behind the stud wall by attaching them with zip-ties. That way you don't have to split the insulation batts to fit them in there.

Thanks Markiz!

There seems to be a lot of differing opinion on whether to plasic the wall or not. After reading here and talking to knowledgable friends I seem to be getting 50/50 answers on the plastic/don't plastic question.

I have a pretty decent gap behind the stud wall in most places. In fact I was able to pull plastic in behind the studs. Should I pull it back out? I only did one (easiest) of three walls so it would be nice if I didn't have to do the other two (harder) walls.
 
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Old 12-21-04, 09:23 AM
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I know what you mean about the 50/50 split I just talked to a few contractors/carpenters in my area and the response was 100% "no poly on the wall". Here's their reason why: if water/condensed vapor gets inside the cavity between the poly and masonry it has little to no chance of ever evaporating or draining properly and pretty soon you have a mold garden growing behind your wall. Also interior water vapor that makes it past the kraft facing can condense on the poly; now you have water inside your wall with nowhere to go. One guy actually said that you could have a set-up with poly on masonry if you somehow were able to tie it into your french drain (kind of a crazy thing to do). Good luck to you.
 
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Old 12-21-04, 10:16 AM
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I think I'm going to go without the poly. The reasons being that I have a good amount of space between the stud wall and the concrete, and the fact that I haven't seen a drop of moisture anywhere in my basement the 3+ years that I have lived here. I think that much of this is due to the good drainage I have outside my house (Excellent slope, good water drainage/direction system) I'm pretty sure that any small amount of moisture that does get through shouldn't have a problem finding somewhere else to go.

Once again I'd like to say thanks. You and this forum have been a lifesaver!
 
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Old 12-22-04, 02:12 PM
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Is it crazy?

Markiz37, you said, "One guy actually said that you could have a set-up with poly on masonry if you somehow were able to tie it into your french drain (kind of a crazy thing to do)." I've been thinking of doing just that. WHen I had the french drain installed, the contractor used a plastic edging around the floor to give a neat floor/wall joint with a 1/4" gap for any moisture to run down the wall into the drain. I thought if I could attach the plastic at the ceiling and direct it (maybe using construction adhesive) to the plastic edging, I'd be managing where that water would go. Is that "crazy"?

Joel
Bayside, NY
 
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Old 12-23-04, 05:48 PM
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Not Crazy..it's the Code

Running plastic sheeting mounted directly to a basement wall into a perpipheral drain is just what building codes require.

Alternately, you can run the plastic over the footer and under the slab prior to a floor slab being poured.

Otherwise, it is usually not allowed for plastic sheeting to simply terminate on top of a floor.

Here is an extremely helpful link to illustrate the proper ways membranes should be used in basement moisture and water control:

http://www.extension.umn.edu/distrib...s/7051-04.html
 
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Old 12-23-04, 09:55 PM
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Question Just so I understand...

I am in the exact same stage in my basement finishing as NEGATIVE (framing and wiring complete). I have a dry basement with good exterior drainage. I also have kraft faced insulation that I am about to start installing and was assuming that I would NOT use any additional vapor barrier. The discussion gravitated towards a barrier against the foundation - this does not seem to be needed in my situation at least ... HOWEVER, just so I understand, is the consensus to use a vapor barrier between the insulation and the sheetrock or no need for vapor barrier (just use kraft face stapled to studs)?

Thanks for the advice, ladies and gentlemen.
 
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