Hi,
We bought a condo for the MIL in Western NC and am wondering if the insulation in the crawl space was installled incorrectly. Here are the details:
1) the basement always seems “moist” in the summer. We have a dehumidifier going in the summer and she needs to empty it every other day or so. (I realize this is in the South where things are hotter than I’m used to View Image, but the place is up in the mountains so it is not unbearably humid for most of the summer.
2) The crawl space is about 5′ high and there is a nice layer of plastic sheathing on the dirt.
3) the joists are 2×10″ and the insulation is installed this way:
3a) (Starting from the subfloor down) – a layer of unfaced yellow insulation.
3b) below that, there’s a layer of R-13, pink, with the paper exposed to the ground)
4) when I took some of the insulation down from a couple of bays it appears to be dry and the joists/subfloor don’t appear damp. (granted, we’re down here for Christmas so it is not that humid, but I don’t see any stains on any of the structure).
Is the insulation installed bass ackwards??
My thinking is that it should be installed this way: (again, starting from the subfloor down)
a) the pink layer first with the paper facing the subfloor
b) the yellow layer next and everything held up with those thin metal wires you put up between the joist bays.
Is my logic correct??
Replies
I'm in central NC, I've got one layer of R-19 in my 1st fl. and it's held up with wire tigers teeth, but it's all yellow! I always thought the paper, or any vapor barrier, was supposed to be to the dwelling side, but I am old, and in turn slow.
Are there foundation vents, and are they open? Could be why it's moist.
We've gone to conditioned crawls. Have to dehumidify after dry in, but it should stabilize before the house is closed on<G>...and everything is closed in, makes a huge difference.
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The moisture isn't related to the insulation.
Most likely, it's related to letting hot moist outside air into a nice cool crawlspace.
Checkout the crawl discussion at http://www.buildingscience.com, e.g., http://www.buildingscience.com/resources/foundations/foundations_moisture.pdf
As the other person said - go with a conditioned crawl.
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The insulation is installed backwards, but I don't think it is such a big deal since paper vapor barrier is marginally effective at best and you say the insulation seems dry. If you are worried about, take a razor knife and slash the paper every foot or so.
Here is something think about: Depending on the exact location, western NC receives up to 100" of rain a year - so, yes, it is damp there... I've even heard it referred to as being located in the Appalachian rainforest.
If you want do do something for your MIL withoug getting nto major re-work, figure how to hook up the dehumidifier so that she won't have to empty it - ie an outside drain.
Edited 12/25/2006 11:35 am ET by Matt
One problem with the paper backed insul in a crawl is that is a wonderful food for mold if it gets moist.In my area, that is usually when it touches the ground, but I've seen mold growing on paper faced insulation installed between the joists.
The "War on Terrorism" has failed - in part by narrowing our options to only the option of last resort.
I propose we start a worldwide Partnership Against Terror, in which the reasonable people of the world work together to oppose terrorism and the conditions which lead people to that desperate condition.
"We hold these truths to be self-evident, that all people are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty and the pursuit of happiness."
right... and at that point it's probably on the floor joists too.
Where "in the mountains"? A lot of WNC is about even with heat vs cooling time. For a long time the standard has been vapor barrier towards the "warmer" side, ie heated side if that is more than the time of the year when you are cooling. We are about 25 East of Asheville just off I-40.
The plastic is sometimes put down fairly poorly allowing a lot of moisture to come up. Also ventilation is either done poorly or totally wrong in many cases. I prefer the thermostatically controlled vents that take the worry out of remembering to open or close them.
Totally sealing everything is supposedly the best but a little involved.
If you cannot get the dehumidifier to gravity drain to an appropriate place you can use a condensate pump to take it away.
This time of the year around here you probably should not see the dehum run. Check for proper drainage away from foundation, gutters, etc. It may be normal but all things considered even with a good bit of rain I usually see no problems.
Bob
Thanks all for replying.The place is in Etowah, NC.I just got done laying another layer of 6 mil poly on the floor, overlapping it about 4 ft and running it up the walls about 6-12". I was careful to make sure it was tight to the walls and tight to the concrete block columns that hold up the center joist. Hopefully that'll help.Yes, there is a fan in there that circulates the air (there are vents down there that let in (and presumably allow to escape) the humid summer air. The fan broke a month or so ago so I went to Lowe's to buy a new one. They didn't have any crawl space fans, but I did pick up a gable end fan for an attic. (I know, I know it won't last as long, but it was only $50 so I don't mind changing it every couple of years).It does have a temp regulator on it and I set it for 65 degrees (where is that little "cicle degree thing" on your keyboard??)I also started to flip some of the insulation, but as previously noted, it wasn't damp so I think this will help only marginally. Got about 40% of the joist bays flipped.So I hope the new poly will do the trick with the aid of the fan.
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