Insulation and Vapor Barriers

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  #1  
Old 12-08-01, 03:36 PM
OldFart
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Insulation and Vapor Barriers

Greets fm CO
I am currently building a geodesic dome cabin in the Colorado mtns @ 9800 ft. Orig I insulated my crawl space foundation (5 ft tall) with styrofoam blue insulation 2 in thick and 4 in thick on the N side. I did this before backfilling. However, when a contractor put siding on, he cut out quite a bit of insulation in order to use 2 X 4s to have something to attach the siding to. I wish to make up for this loss in insulation if possible by insulating the inside of crawl space foundation wall. Can I do this w/out trapping moisture within the wall and running a chance of this moisture freezing and damaging the concrete?? I did apply 1 coat of Elasto Seal, a rubberized waterproofer to the outside of my concrete wall before backfilling. Should I still use a vapor barrier on the inside wall?? It is backfilled now and the siding is on so I cannot add more insulation on the outside.
Also, where should I apply a vapor barrier on the subfloor.
I had to put a layer of this same waterproofer (elasto) on top of the floor, the floor is OSB and a death in the family precluded
closing in for 3 wks. Thanks
 
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Old 12-08-01, 06:42 PM
R
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Vapor barriers are only applied between conditioned spaces and unconditioned spaces. Since the crawl space is an unheated area or unconditioned space, the wall of the crawl space should not have a vapor barrier but the first floor or ceiling of the crawls space should. The Dept. of Energy states that areas that experience 8,000 degree-days or more, which Colorado does, the vapor barrier should be between the living or conditioned space and the insulation. Vapor barriers, regardless what type it is, does not address conductive heat loss. It is heat that contains moisture. There is no known product to man that can eliminate conductive heat loss. All vapor barriers do is limit the amount of moisture, there by reducing it chances of it condensing concerning heat flow. If you look at vapor barriers the performance rating is usually SP-15. The SP stands for static pressure, that's fluid mechanics. There is very little thermal effect. Thermal effect is rated in "R" values, like with fiber glass insulation. The "R" stands for resistance to heat flow. So when you are considering heat loss, the performance rating you're looking for is "R" values and when you're considering moisture problems, the performance ratings you're looking for is "SP". These ratings are standards and are listed by the Bureau of Measurement and Standards. When considering insulation and/or vapor barriers, those are the ratings you should be looking for.
 
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Old 12-10-01, 06:53 AM
OldFart
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Insulation and Vapor Barriers

The answer to my previous post answered only part of my questions. Possibly that is my fault by asking too much in one post. Unanswered Qs:
1. Would the fact that I have the Elasto Seal (rubberized waterproofing) coating on the subfloor affect me putting a vapor barrier between the insulation and the underside of the subfloor?? Would it trap moisture in the subfloor??
2. Would it be practical to put insulation on the inside wall of the crawl space??
3. What type insulation should I use if my second Q has an answer of yes??
Thanks
 
  #4  
Old 12-10-01, 01:50 PM
rbisys
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Greetings,

You're working against yourself.

If I understand correctly you have 2"-5" of foam on the exterior crawl space walls. The system you have constructed is similar to an ICF wall system. You shouldn't have to insulate the floor.

The additional floor insulation will isolate the crawl space and it will freeze, not counting the condensation, mold and dryrot problems. If the wall performs as it should then the only other thing you have to do is eliminate the earth absorbing the floor heat that is radiated to it. Since you are probably more concerned with heat loss in the winter then I would recommend the following. If you have plastic over the earth you only have to lay a radiant barrier sheet over the plastic. This will reflect about 97% of the heat energy back to the floor. The crawl space temp shouild be close to the upstairs temp. You will not have any condensation, mold or dryrot problems.

If the foam is not effective, as could be the case as you do not have a true ICF condition, then a radiant barrier applied to the inside of the wall will provide the performance you desire. However the concrete will then be as cold as the outside temperature and the foam nulled.

I hope you didn't FG the shell.

Thank you for considering my opinion.
 
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Old 12-11-01, 05:08 PM
OldFart
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Insulation and Vapor Barriers

Rbisys and anyone else
I am using polyisocyanurate insulation in the shell. I have found a source where I can buy it very economically. I am forced by bldg inspectors to make a venting system between roof sheathing and insulation by drilling holes and installing vents at top and bottom of house. Also, I plan to install a vapor barrier
on the ground in crawl space and on complete inside of living area between insulation and dry wall. I have to use the polyiso insulation to meet bldg codes for R values of insulation altho I believe air infiltration is more important than insulation. I have used bunches of spray foam and also used tyvek between sheathing and siding to try to tighten up house. Wish me luck, I only have 1/2 of roof shingled but have Grace Ice and Water shield over entire roof.
Thanks for your comments
 
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Old 12-12-01, 01:17 AM
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If you want more information on building performance search the web for energy conservation and look for Proctor Engineering out of Colorado. They're considered the best in building performance specialist in this country. They consult for 7 power utilities on energy conservation programs that I know of. Once on their site, if you e-mailed them, I'm certain they would reply.
 
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