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Crawlspace insulation upside down

tjohns's Avatar
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05-09-03, 07:32 AM   #1  
Crawlspace insulation upside down

I am currently in the process of buying a house in central Indiana. I had the house inspected and the inspector said that the insulation in the crawlspacw was installed upside down with the vapor barrier on the wrong side. Is this a big concern and shoud I have it removed? Also, do I need crawlspace insulation if the ground in dry?

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resercon's Avatar

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05-09-03, 11:37 AM   #2  
You don't need insulation on the ground but rather you need a moisture barrier. Even though the ground may appear to be dry, there is moisture in it. The difference between the ground inside a crawl space verses the ground outside is that the moisture in the ground outside evaporates into the atmosphere, whereas the moisture in the ground inside a crawl space evaporates into the crawl space. This will increase the humidity level throughout the house through what is known as Equilibrium Relative Humidity (ErH%). And this will promote mold and mildew growth. Laying plastic over the ground in a crawl space prohibits the moisture in the ground from evaporating and forces it to do so outside the crawl space where it can do no harm to you, your family and/or the structure.

Insulation prohibits or slows down heat flow and a vapor barrier, which are only applied to insulation, slows down moisture flow. Since the heat will travel from inside the home towards the crawl space you wish to slow down the moisture flow before the heat goes into the insulation. If the moisture is slowed down after it has gone through the insulation, condensation will form there. And the same problems mentioned above with mold and mildew will occur.

As a Home Inspector, I would have done more than just cautioned you in this case. I would have told you to have the insulation taken down and the area termite inspected before purchasing the house. If the seller refused to allow this inspection, then I would have told you to obtain a letter from him stating that he accepts responsibility for any wood destroying insect damage to this area for a specific period after the closing of the house. Let's say 2 weeks afterwards.

Insulation installed backwards under these circumstances promote the infestation of wood destroying insects. It would be prudent to remove the insulation, have it inspected by a professional and if there is no insects or damage, reinsulate this area correctly.

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