Insulation, Radiant and Vapor Barriers - Vapor Barrier
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mflo64
01-28-03, 11:38 AM
I have a 2 foot crawlspace underneath my house and would like to insulate it. I've read that vapor barriers will prevent any moisture from causing mold and mildew and musty odors into the first floor closets and other areas where there are gaps on the subfloor.
How do you install a vapor barrier? I've read that some put it over the dirt, and others tape it to the sub floor underneath? What's the easiest and most effective method?
How do you install a vapor barrier? I've read that some put it over the dirt, and others tape it to the sub floor underneath? What's the easiest and most effective method?
resercon
01-28-03, 12:22 PM
http://www.eren.doe.gov/consumerinfo/refbriefs/bd4.html This a Dept. of Energy brief on Vapor Diffuser Retarders (VDR) another name for vapor barriers and Air Barriers.
Moisture barrier and vapor barrier are used interchangable but they are different. Moisture barrier is used to prohibit evaporation and pressure induced moisture transfer. Either through hydraulic or atmospheric. When you cover a dirt floor with plastic, the plastic is a moisture barrier.
Vapor barrier is only used with insulation. It is designed to prohibit moisture transfer concerning heat transfer through materials. This is because all heat has moisture in it. The insulation slows down the heat flow and the vapor barrier slows down the moisture flow. If you slowed down the heat flow and didn't slow down the moisture flow, when the heat reached dew point temperature, it would condense the moisture in the heat.
Both applications are used to control moisture problems in crawl spaces. Covering the dirt floor and installing insulation up against the subfloor with the vapor barrier touching the subfloor reduces the probability of moisture problems in the crawl space. If you live in a cold climate, ventilation of the crawl space will also reduce the probability of a moisture problem from occurring. Ventilation in both your crawl space and your attic is based upon Equilibrium Relative Humidity (ErH%). Basically all that means is that air at a lower Relative Humidity (outside air) will absorb humidity from air that has a higher Relative Humidity (inside the crawl space), thereby reducing the Relative Humidity in the air in a confined space (attic and/or crawl space).
If you reduce the probability of moisture from occurring inside the crawl space, you reduce the probability of mold and mildew occurring inside your closets. This is because the source of the mold and mildew is moisture.
Moisture barrier and vapor barrier are used interchangable but they are different. Moisture barrier is used to prohibit evaporation and pressure induced moisture transfer. Either through hydraulic or atmospheric. When you cover a dirt floor with plastic, the plastic is a moisture barrier.
Vapor barrier is only used with insulation. It is designed to prohibit moisture transfer concerning heat transfer through materials. This is because all heat has moisture in it. The insulation slows down the heat flow and the vapor barrier slows down the moisture flow. If you slowed down the heat flow and didn't slow down the moisture flow, when the heat reached dew point temperature, it would condense the moisture in the heat.
Both applications are used to control moisture problems in crawl spaces. Covering the dirt floor and installing insulation up against the subfloor with the vapor barrier touching the subfloor reduces the probability of moisture problems in the crawl space. If you live in a cold climate, ventilation of the crawl space will also reduce the probability of a moisture problem from occurring. Ventilation in both your crawl space and your attic is based upon Equilibrium Relative Humidity (ErH%). Basically all that means is that air at a lower Relative Humidity (outside air) will absorb humidity from air that has a higher Relative Humidity (inside the crawl space), thereby reducing the Relative Humidity in the air in a confined space (attic and/or crawl space).
If you reduce the probability of moisture from occurring inside the crawl space, you reduce the probability of mold and mildew occurring inside your closets. This is because the source of the mold and mildew is moisture.