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Vapor barrier and rigid foam insulation, good for basement?

Vapor barrier and rigid foam insulation, good for basement?


  #1  
Old 01-23-06, 10:14 AM
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Vapor barrier and rigid foam insulation, good for basement?

I have a concrete block basement and have been considering insulating (with rigid foam), adding a vapor/moisture barrier, and paneling.

I have read a great deal on this but can't come to a consensus on whether I should use rigid foam insulation and/or a vapor barrier (plastic sheet).

I live in Iowa (cold winters and hot humid summers).

Does insulating the basement hamper the benefits of the basement being below ground? In the summer the basement is always comfortably cool, albeit humid, because of the constant temperature of the ground outside the concrete blocks.

If I insulate, I won't get those cool outside temperatures in the basement, right?

Regarding a vapor barrier, I don't see how this can prevent moisture and/or mold/mildew growth. Won't moisture develop, in the summer, on one side of the vapor barrier? This would seem to increase the likelihood of mold.

Any recommendations/suggestions?

Thank you.
 
  #2  
Old 01-23-06, 11:24 AM
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Both questions are moot. The insulation will not affect the temperature moderation that a basement experiences, just the speed at which the basement will get warm or cool. As for the vapour barrier, it will not stop the amount of humidity in the basement, just how much that humidity will affect the insulation you are planning to install.

J
 
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Old 01-23-06, 11:37 AM
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per the dictionary:
a moot question is one that is arguable or open to debate
.

Let's debate...
 
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Old 01-23-06, 02:22 PM
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Uh huh, but which dictionary? Let's debate that one: Oxford v. Webster. I will stick by my assessment of insulation performance in the basement.

Actually, I was going to ask if insulation in a basement ceiling needs a vapour barrier considering humidity in a basement is much greater than upstairs.

J
 
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Old 01-24-06, 08:52 AM
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I'll bet you that the quantity of moisture in the basement is the same as the rest of the house, but since cold air can hold less moisture than warm air, it means the RELATIVE HUMIDITY in the basement (cold air) is higher than in the rest of the house (warm air).

Next, if you have a humidity problem in the basement, putting a VDR in the ceiling will worsen it:
Your basement relies on drying to the rest of the house. The rest of the house should have bathroom & kitchen fans (or preferably, a dedicated mechanical ventilation system) to manage moisture. So the best way to manage basement moisture is to NOT put in a ceiling VDR.
 
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Old 01-24-06, 10:05 AM
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Originally Posted by doug thomas
I'll bet you that the quantity of moisture in the basement is the same as the rest of the house, but since cold air can hold less moisture than warm air, it means the RELATIVE HUMIDITY in the basement (cold air) is higher than in the rest of the house (warm air).

Next, if you have a humidity problem in the basement, putting a VDR in the ceiling will worsen it:
Your basement relies on drying to the rest of the house. The rest of the house should have bathroom & kitchen fans (or preferably, a dedicated mechanical ventilation system) to manage moisture. So the best way to manage basement moisture is to NOT put in a ceiling VDR.
What is a VDR? Ventilation D------------ R--------
 
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Old 01-24-06, 12:29 PM
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VDR = vapor diffusion retarder.
This category refers to any material with a perm rating less than 1. Polyethylene, with a perm rating at 0.04 - 0.1 falls under this category.
 
 

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