Seeking your wisdom on a 1.5″ radiant slab that will be going in on my first floor. I am owner/builder on this project in case you’re wondering. Due to some delays between erection of the timber frame and arrival of the SIPs, I’ve covered the deck with Ice & Water shield as you can see (trying to avoid a skating rink in the basement).
Is is OK to leave the IWS under the concrete slab when we pour? I thought I had seen some warnings against interior use – outgassing maybe?
-Peter
Replies
You're concerned that the heated tubing right against the Grace will soften it enough so you could smell it down stairs?
That's the reason rosin paper instead of builder's felt is recommended between plated sandwiched PEX and hardwood, but not exactly the same situation. If you leave the membrane there, you would probably get a marginally stronger slab as there would be zero moisture migration from the concrete into the subfloor.
This should be an interesting thread.
Edited 1/10/2006 12:39 pm ET by johnnyd
That's right - I am worried about the ice/water shield membrane heating up and it causing a smell, or possibly releasing unhealthy petroleum based fumes into my living space. I have a Radiantec plan for the system and I will ask them too, but first wanted to tap the experience of this group.
I should add, I've seen a lot of recent discussion on gypcrete on this board but relatively little about concrete slabs. I have a 5" concrete slab with 1/2" PEX in the basement, and plan to use a 1.5" concrete slab on the first floor. The deck is designed to support the weight of the concrete, 14" I-joists 16"OC with 11' 6" spans. I will supplement it with a wood stove to give faster response when it's needed. I have not fully decided what to do on the 2nd and 3rd floors but am leaning toward Warmboard.
From what I've heard (FWIH)over several years of research (resulting in a sucessfull 100% DIY low mass residential radiant floor system, and an in-slab shop heating system) you're better off with concrete, as the plus side of Gypcrete is LIGHT WEIGHT, it's downside is excessive shrinkage and high cost. Since you're already engineered for concrete, you'll get the benefits of high mass with little if any downside.
Why even risk the fumes? What would be the benefit of leaving the ICE & WATER down?
Also FWIH, good choice on the WarmBoard...superior emitter and cost effiective if installed at time of new construction.
What's your climate, by the way? # of HDD?
You might also want to peruse the many threads on:
http://www.radiantpanelassociation.org/i4a/pages/index.cfm?pageid=1
Edited 1/10/2006 4:12 pm ET by johnnyd
johnnyd - thanks for your comments. BTW, it's central coastal Maine ... about 3000 HDD per year.
Edited 1/10/2006 6:04 pm ET by shearwater
3000?We're more in the 7000-7500 range, my friend!-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
You shouldn't need fast response if you run the system properly (ie. set it and forget it).You didn't mention your heat source, but generally some sort of reset with PWM thermostats results in dead locked room temps.. very excellent... and consistent operation during different parts of the season.The only issue I would see is if you are trying to do setbacks (don't, not with 'crete anyway), or if you get heavy solar gain which will result in an overshoot, not an undershoot.What I'm saying is the wood stove is not helpful unless you need supplemental heat because the floor won't keep up under design, and if that's the case, make sure the wood stove heated area is zoned by itself.Sorry I can't answer your membrane question though, I'm not familiar with the product myself.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Nice project!
Among my concerns, were it my house, would be the long-term (or maybe even short-term) degradation of the PEX tubing being in contact with the petroleum-based solvents (exact type unknown and variable in the product itself) present in the membrane. And any adverse effects been amplified by the higher ambient temperature.
I would assume that the tubing is being stapled down directly onto the surface of the IWS and would be in direct contact with it. I would expect that the manufacturer of the tubing would advise against this. Ask them. If they say no then all other considerations are moot.
I do know that Wirsbo does not recommend the use of electrical tape to secure their tubing. I asked them after I saw an installer doing it.
Or - tear it up. The upside - you avert possibly severe consequences. The downside - a little time spent tearing it up after it's done its original job.
- Brian.
What I recommended too....why not just tear it up? But now, thinking about it...that stuff STICKS, and was never designed to be taken up.
Any one ever removed Grace IWS?
Done deal. The Grace is coming up! The cold weather in Maine has actually kept the stuff from sticking properly, it should come up easy enough. I'll wait until the SIPs are up, though (Jan. 23!). Then, we'll rip up the Grace and get my kids to help staple down the next 3 coils of PEX! There is not all that much that they can/will do, but here they are fastening down the tubing in the basement slab, they really came through!
Thank you all for your advice.
Peter
"Any one ever removed Grace IWS?" More of it than i'd ever wish on anyone!!! Some by TUGGING (and I mean TUGGING) and scraping, some by actually having to cut out plywood. If it has been being walked on during the erection of the frame, it may be a nightmare to remove, it may also leave behind enough of the stickiness to not eliminate the concerns about how the radiant heat may off gas it. Good luck!
NRTRob,
Oops about the Heating Degree Days... I looked up the answer to the question in the post on the NOAA site, http://iwin.nws.noaa.gov/iwin/me/climate.html and I guess I pulled the number under "since July 1" - about 3000 - instead of the yearly number.
Since the house is going to be a weekend/vacation house, the setbacks will be left at 50-55 deg for long periods. The idea of the wood stove is not meant really as a supplement, but to warm the place up as you arrive on a chilly Friday night while waiting for the slabs to come back up.
I haven't made a final decision on the heat source yet. It will have 2700 sf of heated floor space including the basement. Radiantec sized it at 80,000 BTU's plus 20% extra and suggested 100K BTU.
That's a pretty high load, averaging almost 30BTUs/sq ft... If it's accurate, I would think you have at least a few areas in the house that radiant won't heat by itself. What's the house construction?Also, I would recommend thinking about a phone switch... call the house before you leave on vacation, it's warm when you show up.edit: if that's remotely accurate though, I would strongly suggest a condensing/modulating boiler for maximum efficiency. Use an outdoor sensor with it.
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-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Edited 1/12/2006 7:25 pm ET by NRTRob
Did Radiantec have specs for SIPS in thier calculations? FWIH, a SIP can be counted on for a solid R20+. I agree with NRT that you may be oversized, unless you have some really big windows. Is the roof going to be SIP as well?
Even at 20BTU/hr/sqft, which is generally easily achieved with modern tight envelopes, you should be more in the 50k - 60k range. You might want to try out your own heat loss calculation with software from Weil-McClain or Mr. PEX.
Here's a good HDD chart:
http://www.ncdc.noaa.gov/oa/climate/online/ccd/nrmhdd.txt
Edited 1/13/2006 8:14 am ET by johnnyd
Well, the walls are 3.5" EPS foam core SIPs (R-16), and the roof is 5.5" SIPs, R-26. There is quite a bit of glass in the plan, about 28% area, and a good amount of the glass is North facing, for views.
I will post again after I've had a chance to study the suggestions on reviewing the heat lost figures.
Can you suggest a manufacturer/source for the phone-activitated controller your mention?
Thanks.
Most plumbing supply houses carry some version of a "freeze alarm", and better models have an incoming phone switch so you can call and toggle the system between a low setting and a regular setting. It requires some wiring, or a central controller capable of taking that kind of output, but it's a nice feature for a vacation home without a doubt.
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-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I suggestion I hope is not too late... Get a real heat loss calculation done, and not from Radiantec. I've not heard very many good stories regarding the "expertise" from Radiantec.
Visit http://www.heatinghelp.com look for "The wall" section and ask your question there, lots of real experts, friendly and helpful. Believe me, you don't want to put this tubing in without first getting the real deal on Radiantec...Good luck.