isolation membrane/vapor barrier bad for leak detection?
We're having our kitchen's ceramic tile replaced with a new ceramic tile. The existing tile's cracked in a few places due (I suspect) to cracking in the slab. Based on magazine articles, we asked our tile guy to use an isolation membrane between the floor and tile so the new tile won't crack in the same way.
We've just heard that the isolation membrane he's using will be a liquid that's brushed on. This made me realize that the stuff also may be a vapor barrier. From what I've read here, vapor barriers are bad in our Eichlers because it'll make detecting leaks in the radiant heat system more difficult -- the helium gas can't make it through the vapor barrier, so the mass spectrometer "sniffers" used to narrow down the source of the leak won't find anything.
So, two questions:
1) Just *how bad* would it be if the isolation membrane turned out to be a vapor barrier? Does it just make leak detection harder, or will it keep us from finding leaks at all?
2) Has anyone else found out whether common isolation membranes act as vapor barriers as well?
Thanks!
Robert
and on the lighthearted side of leaks in a slab, I saw the following Web article from a heating contractor in Denver who has heard of, but not tried, helium detection. Man, if someone jackhammered three holes in my floor and came up dry, I'd be furious...
http://www.contractormag.com/articles/column.cfm?columnid=132
"Sometimes, things don’t work out exactly right, and your efforts are stymied by heating lines crossing underneath each other or by varying thickness of carpet and pad. The only way to confirm the leak at this point is to do destructive exploratory surgery. This means break out the jackhammer and carefully expose the heating line. Have you ever tried to operate a jackhammer delicately?
"If the area below the slab is muddy, you’re close. If it’s dry, keep sleuthing. If you’re not extremely careful, you may create your own leak with the jackhammer.
"In the case of this job, we opened the floor in three different “hot” spots and found dry dirt.
I would contact a local leak detection company for confirmation, if you have not already done so. Some of the radiant heat companies that advertise on this site, also do leak detection, while others refer this out. Either way, the expert opinion would be best. I know/have heard, that there are newer methods available and perhaps these do not have the same problem with vapor barriers. FWIW, vapor barriers are essential for installing hardwood or cork over most slabs, so they must be quite common - just a guess.
Good luck!
It looks like the answer is "don't use an isolation membrane." Our contractor's supplier said all of the isolation membrane products are also vapor barriers. (It sounds like most of the membranes are elastometric acrylic coatings (like our foam roof coating) with a fabric embedded in it.) Lipp Radiant Heat said to avoid anything that would be a vapor barrier other than 15 lb roofing felt.
We've decided it'll be cheaper to replace any tiles that may crack than to have no way to detect the location of a leak in the radiant heat.
Robert
