Membrane under lt.wt. fill/radiant heat
Greetings –
We’re approaching the point where we’ll be installing the tubing for our hydronic heating system – PEX tubing in 1 1/2″ lt. wt. concrete fill over plywood subfloor & 2 x 10 wood joists. We have the engineer’s blessing on the structural aspects but after spending several years in the ceramic tile industry, I know I need to install a membrane over the floor, under the concrete.
Wirsbo doesn’t like any kind of petroleum product (eg tar paper) adjacent to their tubing. Laminated Kraft paper doesn’t seem very sturdy given there will be quite a bit of traffic over it during the tubing installation. My heating guy says most installations use Tyvek. What little research I’ve done on Tyvek to this point leaves me in doubt of the advisability of using that product.
To complicate matters (perhaps), we’ll be installing granite or marble tile over the entire main floor where this heating system is being installed. This requires an anti-fracture membrane which in turn acts as another vapor/moisture barrier, no? In all my experience in the building industry, it’s always been my understanding that one shouldn’t have more than one vapor barrier in a floor/wall system and it should be located as close to the heated side of the system as possible.
So….the question is, what does this group suggest? I’m severely paranoid about dry rot, water vapor migration, etc., etc. All this is costing me a sizable chunk of change and I only get one chance to get it right.
Many thanks for any suggestions or comments.
Replies
Dennis:
There are many opinions on all aspects of Radiant Floor heating and installation. I have run into many of them as I am installing a system in our home addition. Many installers have things that they like and don't like. Tomorrow (Thursday) I am installing Thermo-Floor (TF) on 2 levels, one is just like your floor, and our lower floor is a concrete pad.
Our designer, Shelter Products, in Portland, is great and very supportive. We are not putting on a plastic sheet on the floor, underneath the tubing. The TF installers spray a sealer on the floor just prior to the pour. This should be ok. On our lower floor, we have 1" Foamular 250 rigid styrene board directly on the concrete. I discussed a plastic sheet with the TF installers and they have never seen one put down. It is VERY important to have the tubes stapled snugly to the floor, with the staples a minimum of 18 inches, so the tubes don't float. In addition, it is VERY important to seal all potential holes and cracks around the floor and around piping as the TF is very liquid and will run everywhere.
Based on my own experience, there are probably 20 ways to do a radiant heat install in the same house.
I just finished a radiant bathroom floor. USe a droduct called Ditra if it works for you. Heres the site. Check it out. Its a little expensive but well worth the money and the ease of use.
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Be floored
Namaste
Andy
"As long as you have certain desires about how it ought to be you can't see how it is."
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