Installing Vapor BarrierIn Crawlspace.

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Old 12-31-13, 10:02 PM
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Installing Vapor BarrierIn Crawlspace.

Hey Everyone. I own a home that is about 2 1/2 years old. It is built on a crawlspace ranging from 3 feet to a little over 6 feet high. It was dry from the time I bought it in September 2012 till about March or April of this year. Then we had record rain in may I believe and it became damp and what appeared to be mold in the dirt and on a few areas. Recently I installed a drain in my garden to redirect the water away from the house better thinking that will help greatly and put a humidity guage to monitor and it read 93%! I recently have done quite of reading and decided I needed to install a vapor barrier in the crawl space. Tonight while inspecting how I would do it I noticed a quite of bit of water/condensation behind the insulation on the walls of the crawlspace. I am thinking that may be caused by the grading on the outside of that particular wall.

Main questions at this time are where does the barrier need to go up to in my crawl space? Is it the top of the concrete or at the top right above the insulation? Also will a 6 mil barrier be sufficient?

 
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Old 01-01-14, 07:03 AM
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Is that insulated wall the outer perimeter of your foundation or a finished basement space? Around here insulation with vapor barrier is installed on the bottom of the floor to separate the heated and unheated spaces. It is not installed on the crawl space walls. On the walls I don't know how you could keep the insulation dry between a damp foundation and damp crawlspace air never mind that all the humidity in the crawl space has access to the home.
 
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Old 01-01-14, 08:43 AM
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Yes these are the walls to the exterior of the home, not a finished basement. It is brick on the outside. So are you saying that typically the insulation should be on the under the floors and not on the walls and the walls would have no insulation? Also while the humidity is very high in the crawlspace it remains around 39% in the home.
 
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Old 01-01-14, 09:06 AM
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You have a challenge ahead of you for sure.
You have a potential water problem as drains can always become blocked or their capacity exceeded. Snow and ice are common issues that can back up rain water and flood a foundation. Providing an internal drain system to a sump pump with power back-up is one rather expensive solution.

Fiberglass on the walls against the brick is a disaster in progress. Even with a vapor barrier perfectly sealed, moisture from the lower area will circulate up to the cold exposed area and accumulate as ice which later melts and soaks all of the insulation. If you can attach some rigid insulation to those walls it provides the insulation without acting as food for the mold. Below is a Building Science link which illustrates some of the wall insulation issues. Yours is a crawl space, but similar issues.

In addition, your crawl floor will need to have a vapor barrier over it.

Bud
 
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Old 01-01-14, 09:48 AM
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Okay thank you. So should I start by removing the insulation on the walls down there and putting insulation underneath the floors of the home??
 
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Old 01-01-14, 10:14 AM
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You need to control the moisture regardless of where you put the insulation. If you insulate the floor, what are you going to do with the crawlspace, it is already at 93% RH. Your solution is to block the moisture from entering that crawl space and then controlling the RH so it doesn't damage that floor structure or carry excess moisture up into the house. If you isolate it, it will become a damp dungeon.

Bud
 
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Old 01-01-14, 10:28 AM
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Okay my plan is to pull the insulation off the walls. Then put insulation under the floors and install a vapor barrier and a Dehumidifier to get the humidity. Also I will block off the vents to the outside. Does this sound like a plan? Also I will make sure the water is directed away from the home.
 
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Old 01-01-14, 10:53 AM
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Sounds pretty good, but, while there is now a lot of science, research, and time proven results in this approach, every house is different, so, personally, while blocking the vents, I would do so in a manner that they could still be opened during warmer months, in case you found that to be the optimal solution.
 
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Old 01-01-14, 01:40 PM
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I am reading some placed that if I have an unconditioned crawlspace with pipes that it needs insulation on the walls. Well I do have pipes but obviously Ihave lots of water and mmoisture behind the insulation. Once I remove it and put it on the floor how do I ensure my pipes won't freeze?
 
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Old 01-01-14, 03:23 PM
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By code here (central NC) the heated space of the home must be totally encased in insulation and vapor barrier. Even if you build a house with a full basement that you intend to heat and finish off in the future, the floor of the main floor must be insulated since the space below is not heated, so they are pretty serious about fully encasing the heated space. There can be no "non conditioned" space within the insulation envelope. So, wrapping the foundation walls with insulation and leaving the floor uninsulated is not permitted.

Typically I've seen where the water lines are tucked up in the floor joist bays with insulation underneath and the vapor barrier facing the crawl space. Most of the water lines are then on the warm side of the insulation. The crawl space is then vented to allow circulation to help keep the humidity under control. Pipes are wrapped with insulation where they leave the insulated space.

My water line passes through the air in my porch's well ventilated crawl space. Where it is exposed I have it insulated and it has never frozen. The ground and house help moderate the temperatures so while the crawl space gets cold it is never anywhere as cold as it is outside. Couple the milder temps with good insulation and occasional water use to warm the pipe & water back up and freezing has never been a problem. But, I'm assuming your winter weather is more severe than mine.
 
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