Installation of hydronic radient heating
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We are owner/builders installing radient heating in southern California, where it is not so common. We have been given conflicting info. We were told by the company making the E pex tubing that we should lay a foil bubblewrap on the wood sheathing before laying the tubing and pouring the “light crete”. Now that we are ready to do the pour and are researching the type of crete to pour we are told that you can’t pour over the bubblewrap. ANY SUGGESTIONS? What kind of cement should we use?
Replies
The bubble wrap is nearly useless as an insulator...maybe some moisture barrier value under a slab on grade, but even then a full 2" of XPS is nearly SOP in colder climates. I can certainly understand why you would not want to put anything heavy over it.
You may want to insulate underneath the subfloor after your pour, to keep the heat where you want it.
Do a search on this forum under "radiant heat" or "gypcrete" or "radiant floor sandwich"
I'm thinking that if radiant floor heat is not done very much where you're at, you may not be able to hire out the gypcrete pour, as that requires some fairly speicalized equipment, technique, and skills.
You also should be aware that a slab is NOT the only way, and often not the best way to accomplish a comfortable, efficent radiant floor. You'll learn that with a little more searching.
Take a trip over to heatinghelp.com web forum called The Wall http://forums.invision.net/index.cfm?CFApp=2
I would recommend talking to Rob at Northeast Radiant Technology http://www.nrtradiant.com/ they designed the system for my home and really seem to know the ins and outs of radiant systems. I've been quite happy with their service.
Tom
Douglasville, GA
Thanks for the kind words Tom.
JMB42; in southern california, using a higher mass method like concrete may pose some issues with the lead/lag time of the mass. I would strongly recommend you use floor sensors to maintain minimum floor temperatures whenever you are in a season where you may have heat demands to minimize the lag on startup, and I would also recommend very good thermostats built for radiant (we like Tekmar 541's or other tekmar 'stats, but other people make good hardware too).
Frankly I doubt you have a high enough heat load to really make radiant floor very attractive.. you probably won't have warm feet even when it's heating. Then again, I'm always stunned with the amount of glass and lack of insulation in milder climates, so maybe it does make sense; a heat load calculation would answer that for you. My suspicion is that radiant ceiling would probably serve you just as well for a lot less money and headache.
and I second the FACT that reflective wrap under concrete is a total waste of time.
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Hi Rob,
Thanks for your input. It is too late to go a different route - we already have the foil bubblewrap laided on the floor sheathing (I guess a waste of time and money) and the ceilings are already drywalled. What kind of concrete doi you recommend and will it do the bubblewrap any harm?
We do have lots of windows but our walls are made of Rastra (10' long "blocks" made of styrafoam and concrete with a R rating of 32.) We are on the coast so it can be quite cool.
We are novices so any info is appreciated.
Dorothy
If you haven't, you should insulate under the floor to keep the heat from bleeding off in "back loss". Regular insulation of some kind, real R-value is needed there.If your bubble pack stuff has an aluminum layer, the concrete will destroy it. This probably doesn't matter much though, because it's not doing anything to help you anyway.If this is a thin pour though, make sure that tubing is no greater than 9" o.c., and frankly in your situation, I would go with 6" o.c. for minimum response times and to guarantee no heat striping during startup conditions, which you'll see a lot of in a mild climate.With that kind of insulation, unless your window area is very large relative to your floor area, I doubt you will notice that the floor is heated much though. It'll be more comfortable than if it weren't heated, but you won't be running around going "oh wow, warm floors!". Definitely use floor sensors to maintain minimum floor temps.Hope that helps!-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com