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Jcotrel1
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# Posted: 31 Dec 2018 06:28am
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I'm buying a small place in the Poconos. I'm sure there is a moisture problem in the crawl space. There is a strong mildew smell in the house. I will look to replace the vapor barrier in the crawl space and replace the carpets with pergo type floors.
What thickness vapor barrier should I go with? Should I also put a vapor barrier down under the floor?
Thanks!
Jim
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fitzpatt
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# Posted: 31 Dec 2018 09:55am
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Generally, from the bottom up, its insulation, then vapour barrier, then subfloor, then finished floor. I have used 15mm thickness, I believe that is .006" thickness imperially, but they say you can go as thin as 6mm. For the price, why not get the thickest you can afford, especially if the area is small.
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Atlincabin
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# Posted: 31 Dec 2018 10:14am
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Fitz, a clarification: probably not 15 millimeters, but micrometers. 15 mm is over half an inch thick!
"6 mil" thickness that you reference is six 1/1000ths of an inch and is fairly tough stuff - that's what I've used.
Jim, from what you describe, it seems likely the moisture is coming up from the ground in the crawl space. The cure for that is plastic on the ground plus some ventilation of the crawl space (a few screened vents would likely do). If the place is heated on a regular basis, you may also want to do what fitz suggested and put a barrier in the floor as well. If it's not heated on a regular basis, you may be able to get away without that vapor barrier.
Good luck.
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fitzpatt
Member
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# Posted: 31 Dec 2018 10:17am
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Yes Atlincabin, that is exactly what I meant. sorry for the confusion. Thanks
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Jcotrel1
Member
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# Posted: 31 Dec 2018 11:36am
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Thanks guys. Atlincabin, yes the moisture is coming up from the ground in the crawl space. The house smells like mildew. The first thing I'm going to do when I close on the place is rip up the carpets.
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rockies
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# Posted: 31 Dec 2018 05:21pm
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It depends on whether the crawlspace is vented or unvented. These articles may help.
https://www.greenbuildingadvisor.com/article/building-an-unvented-crawl-space
https://www.greenbuildingadvisor.com/article/details-for-a-closed-crawlspace
https://www.greenbuildingadvisor.com/article/five-ways-to-deal-with-crawl-space-air
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Jcotrel1
Member
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# Posted: 1 Jan 2019 08:27am
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I know there are small windows. Not sure if they open or how sealed they are. I have to get in there and check it out.
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Jcotrel1
Member
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# Posted: 23 Mar 2019 09:42am
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Just getting back to this thread. So I bought the house. I also bought vapor barrier. The crawl space does have windows with screens. There is foam insulation on the walls.
What is the best way to secure the vapor barrier? Is there a special tape, pins , duct tape? Also, how high up the walls should I put the barrier? Go over the insulation or take it down, put the vapor barrier up then put the insulation back up?
Thanks.
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Aklogcabin
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# Posted: 23 Mar 2019 11:44am - Edited by: Aklogcabin
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Hello Jcotrel1 , I would suggest. Vapor barrier on ground. Where there is things such as a water line where you have to cut around make sure you tape your seams. Use vapor barrier tape. The stuff I use is red . Go up the walls a foot and tape. You are sealing the moisture out. Keep ventilated as much as possible. And use a fan if can to provide air movement. If you have an access hole open it.
I would also try to make sure any run off of rain is diverted as far away from your footing as possible . Rain gutters. On insulated slabs it is a good idea to put rigid 4’ blue board insulation around the outside perimeter of the foundation. Sloped slightly away from your foundation or floor. Protects from frost but also diversts water away. I believe they sell water proof membrane material for this. For what you may be dealing with. Kind of wanted to give you a visual. Can also do a frech drain. A ditch that collects water. A shallow 12†or so ditch that has a 4†pvc pipe with holes in the top. Setting on a shallow bed of drain rock . Like 3/4†rock . D 1 gravel works good, so you can slope it to drain away. Lay a filter material over your drain pipe so fine material does not enter into it. That is then filled with drain rock that diverts the water. You can look it up.
These are simple, fairly inexpensive ways to protect your investment. The more you do the better. Especially if you already have moisture problems.
Hope this helps.
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ICC
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# Posted: 23 Mar 2019 01:42pm - Edited by: ICC
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Living in the SW I normally have the opposite problem, not enough humidity or water. I do not know the Poconos but it seems to me that for at least part of the year your humidity must be classed as high.
If so, what research have you done? It used to be thought that we had to ventilate crawl spaces no matter where we were located. It used to be thought that in a high humidity area we had to have ventilation to move air through a crawl space. Turns out, that is not true when the humidity is medium to high. The air under a house is usually cooler than the exterior air, except when the weather is freezing. Moving exterior air, that is warmer, into a crawl space results in the warmer air cooling. It may cool enough to drop to or below the dew point. That then causes water vapor to condense on the nearest cool surface. Move more air, like fan assisted, through the crawl space and you just make things worse, not better.
So, before you go doing anything make sure it is the correct thing. Chances are you need to seal the ground surface and follow the new ideas that have some science behind them. I think they now call the best way "encapsulating" the crawl space. I'd check on the buildingscience site. They have always been in the forefront of science
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toyota_mdt_tech
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# Posted: 23 Mar 2019 06:17pm
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I'd make sure crawl space had adequate venting and then a black 6 mil plastic on the ground, then a breathable one under the floor below the insulation like a tyvek etc.
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Aklogcabin
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# Posted: 24 Mar 2019 11:32am
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Per Icc . Just my opinion.Usually don’t get into discussions on the web but to suggest not using a fan to help dry out a moisture problem in a crawl space or basement for that matter is just not correct. Usually the first thing done whenever a home has water damage is to get the fans going. Most tool rental companies have commercial fans for rent such as the commercial guys who repair water damage. Mold grows where there is no air flow to carry away the moisture.
In your example you mention the crawl space cooling the air that will enter from the warmer upstairs dry air. I suspect that the crawl space would warm up , not cool down. The air from upstairs is also dryer. The stale fully moisture saturated air in the crawl space must be removed. And steps taken to prevent further damage. Like good ventilation.
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NorthRick
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# Posted: 24 Mar 2019 01:18pm
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I think the point ICC is trying to make is that different places are different. And, different seasons are different. How you effectively deal with crawlspace moisture won't be the same everywhere or every season.
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ICC
Member
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# Posted: 24 Mar 2019 06:44pm
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Quoting: Aklogcabin In your example you mention the crawl space cooling the air that will enter from the warmer upstairs dry air. I suspect that the crawl space would warm up , not cool down.
NOT moving the "warmer upstairs dry air", as was quoted. Venting a crawlspace usually moves OUTSIDE air into the crawlspace, not air from the interior. In a HUMID climate that can produce problems.
@NorthRick, yes solutions are different in different climates.
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Do a search on the building science corporation website. They have been in the forefront of applying science to building solutions for a couple of decades now. There is some very good info there. Google can find their site. Greenbuilder also has some good info.... rockies linked to some.
Some of the solutions though are meant for homes that have continual occupancy and therefore have heating or cooling apparatus operating as needed all year. Those ideas won't be much good in a part-time residence.
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Aklogcabin
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# Posted: 25 Mar 2019 11:06am
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Wow someone has a different opinion and some others. Why the big deal. Guess I figure I don’t need to go read about it on the web to be an expert. I went to college for 2 years for RHVAC . Pretty much everyone has different circumstances and can find answers.
The OP asked about a moldy smell in a house and the need for a proper vapor barrier. I was only suggesting getting rid of the old stale air. And some steps on how to deal with it. Added in the part about slabs because it comes up often and thought it may help some other folks dealing with problems.
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