basement/crawlspace insulating for cold floors

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  #1  
Old 12-06-04, 02:56 PM
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Location: grand rapids, michigan
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basement/crawlspace insulating for cold floors

wow great site, lots o info, i love it.
ok so heres the Q part of the Q and A ... i have a 91 (best guess) yr old home in grand rapids michigan, its a 2 story with basement dont know if it was originally a biplex home or not but it is now. and both levels or units are laid out identical. the back side of the home has the back porch(S) and bathroom(S) these spaces were not original and do not sit over the basement. rather these spaces have crawlspaces underneath. the bathroom sits to the north and the crawlspace is accessible from the basement (accessible used loosely there is about a hole between the basement and bath crawlspace that looks like i can get through) the back porch crawlspace has a small access door from the outside. the problem is cold and energy costs. neither crawlspace has insulation between the floor joists or any type of plastic sheeting on the ground. what can be done to remedy the cold floors? thanks for all replies
 
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Old 12-11-04, 07:56 PM
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If the porch is not heated, then insulating the floor is not going to make a difference. The bathroom floor poses a problem because of the plumbing. Here I would recommend insulating the walls of the crawl space and laying a moisture barrier (6 mil plastic) over the dirt floor if there is one in the crawl space. I would also recommend leaving the access from the basement open and checking the crawl space periodically for signs of moisture.

In this application it is important to control the sources of moisture, regardless of the season. Since the vapor and moisture barriers are away from the bathroom floor, the crawl space may produce a moisture problem. If there is a shower stall or bathtub in this bathroom, you have to have a bathroom exhaust fan that exits the house. All your water pipes should be insulated in the crawl space to avoid condensation, especially on the cold water pipes during the summer. Also inspect you drain pipes in the crawl space for any signs of leakage.

Even then, there will still be a constant flow of heat that contains some moisture in it that will enter the crawl space from the bathroom floor. The vapor barrier on the insulation and the moisture barrier on the floor will prohibit this moisture from being absorbed. This is why leaving the access open to the crawl space from the basement is important. The air in the basement will absorb the moisture that manages to get through the bathroom floor and it will be absorbed by the mansonry walls and floor in the basement which will expel the moisture out of the house.
 
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Old 12-14-04, 02:29 PM
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vapor or moisture barrier or both??

thanks much resercon, i appreciate the reply, and have one question regarding that reply, you make reference that it is important to control the sources of moisture since the vapor and moisture barriers are not touching the bathroom floor. are these two things the same? (in theory is the paper facing of insul. the same thing as 6mil plastic on the dirt floor in the crawlspace? they both do the same thing or separate purposes?)
 
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Old 12-14-04, 04:36 PM
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The terms moisture and vapor barriers are frequently interchanged. However, in my industry, vapor barriers are only used with insulation. This directly associates vapor moisture with heat through diffusion. So the primary purpose of vapor barriers is to retard heat transported moisture. Whereas moisture barriers primary purpose is to prohibit liquid moisture flow which can evaporate. Examples of moisture barriers are basement water proofing paints and the plastic laid on the floor of a crawl space. Moisture barriers primarily deal with capilliary action in ground water. Which means moisture barriers are only applied to below grade areas of the structure.

To further distinguish between the two is that a moisture barrier function goes from outside ground water (liquid) to penetration into the structure to evaporation (vapor). A vapor barrier function goes from heat transported moisture (vapor) to avoid condensation (liquid). So the direction in which the moisture flows also distinguishes them. With vapor barriers the moisture flow is within the structure to the outside and with moisture barriers the moisture flow is outside the structure to the inside.

It really does not matter which term you use but if I say vapor barrier to someone in my industry, they immediately associate it with insulation. If I say moisture barrier, they immediately associate it with a below grade application because everything above grade in structures are water shedding systems, with the exception of low sloped and/or flat roofs.

Vapor and moisture barriers in most cases have the same characteristics or Perm Rating but their functions are different.
 
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