radon/vapor seal and insulation


Old 07-02-04, 07:57 AM
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radon/vapor seal and insulation

I have a full basement with poured concrete walls and my house was built in 1968. I live in an arid climate (Northern Utah). The basement doesn't leak. I have done extensive research, and can't find any information on the following question. Does applying a radon/vapor seal (RadonSeal, Dryloc) to the face of my concrete and then finishing the basement with traditional stud wall framing and fiberglass batting with a vapor barrier on the warm side constitute a 'double barrier'? I have read of moisture condensing between a double barrier and becoming trapped, resulting in inevitable mildew and fungus in the insulation. I have not found mention in any basement remodeling books or websites that addresses using a concrete seal in conjunction with framing & insulation. Any advice would be appreciated!
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Old 07-03-04, 08:41 AM
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Just my opinion. Others may disagree.

Since you live in an arid climate, I would say to do nothing to the concrete walls before framing. I would, however, get a radon test first to see if you should do radon mitigation before even starting your project.
Old 07-03-04, 09:53 AM
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Hello: mnlop

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Old 07-04-04, 07:35 PM
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This site will give you a list for homeowner testing kits. John is absolutely correct, test first and do not Drylock the basement walls if they are dry. What most people overlook is that moisture absorption and expulsion works both ways. Equilibrium Relative Humidity (ErH%) states that an object with a lower humidity level than the objects surrounding it, that object will absorb humidity from the objects surrounding it until the humidity level is equal to the objects surrounding it. We know that there are a variety of sources of humidity within a structure, such as a washing machine, dryer, pets, humans and a lot more. Judging by your statements, I can conclude that your basement walls are a major reason why your basement is dry. And Drylocking the walls may produce the exact oppposite effect you wish to accomplish. And you are correct that Drylock can qualify as a vapor barrier in some instances. Or as you put it a double vapor barrier. In reality it violates the 5 to 1 rule with materials applied after the vapor barrier. So does roofing materials, but there are ways to circumvent the effects of the low vapor permability of roofing materials, as there are ways to circumvent the low vapor permability of Drylock.

Another way of putting this is time and distance. For example, the basement walls are absorbing and expelling the humidity produced within the structure like if you traveled 60 miles at 60 miles per hour. It would take you an hour to reach that distance. You apply Drylock to the wall and you travel the same distance but at 30 miles per hour. It takes you two hours to reach that distance. Drylock can actually increase the humidity levels in a basement, especially in area where the basement is dry and the climate is too.

For your information I am a licensed Radon Measurement Technician in the State of New Jersey, license number MET 11803 and I have never recommended Drylock in radon mitigation.
Old 07-05-04, 03:10 PM
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Thank you - I truly appreciate your in-depth answers to my question. I will let you know how it turns out (and I'll test for radon first).

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