bob in edmonton
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Posts:16
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| 03/04/2008 12:37 PM |
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I am getting close to the stage of pouring the basement slab. It will be insulated. Planning on 2" styrofoam. Is good, yes?
Should a vapor barrier be placed under the foam?
Soil is clay, with gravel to appropriate level, with sand on top. What thickness of material? I assume poly. True?
Hydronic radiant will be in the slab. Thickness 4" at this time.
Whike on the topic of radiant, would it be worth the trouble to
have different zones in the same floor? The loops of the zones
would be adjacent to one another, alternating. My (simple) reasoning is
that I may not need to pour a lot of heat into the slab most of the
time, so one zone could remain off, and be called when necessary. Would
this cause too much thermal "stripmg", and is that a bad thing? There
will probably be a short pile carpet as floor finish.
bob
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NRT.Rob
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Posts:384
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| 03/04/2008 12:45 PM |
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6 mil poly is pretty standard. it's always under the foam around here in maine.
the only reason to 'stage zone' the floor is perhaps to do high traffic areas and less travelled areas. then, you can make the less travelled areas warm first, instead of the whole floor being cooler to the touch.
But frankly I think that's a ridiculous thing to do... I'd rather be heating with the 80 degree water all over.
If you want to vary output with load, use a reset control to change your water temperatures. |
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warmsmeallup
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Posts:83
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| 03/04/2008 5:07 PM |
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Try researching this product. We've used it many times with great success...
thebarrier.com
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Comfort Radiant Heating |
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NRT.Rob
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Posts:384
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| 03/04/2008 5:16 PM |
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| the barrier has a lesser R value than 2" of foam.. half or less. This might be acceptable under some slabs, but R10 is a typical Rvalue specification for a heated slab, not R3.5 or R5. |
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warmsmeallup
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Posts:83
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| 03/04/2008 5:24 PM |
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| Just curious, where does the R10 value standard come from? |
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bob in edmonton
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Posts:16
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| 03/04/2008 5:50 PM |
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The point made by the company
http://www.nofp.com/
is that 3/4 inch of this is as effective as 1 1/2 in of foam
board after it has been brokrn by walking on it as well as the spaces
along the boards. You don't wind up with what you think you put in the
ground. The way it seals is a better barrier than trying to seal poly.
Labor is a lot less.
They quoted me $159 for a 4x6 ft roll. 66 cents/sqft.
Incidentally, they are coming up with a 1 1/4 in version.
bob
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warmsmeallup
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Posts:83
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| 03/04/2008 6:15 PM |
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I am in no way a hydronics expert..in fact more of a laymen. My speciality falls on electric radiant but we use insulators too. Aren't most hydronics designed for R5?. And, the RPA just had an article ( month or so ago) that stated R3.5 - 5. It's my understanding that 2" was used becaue it was easier to walk on then 1", which is what was spec'd. A waste of money to me.
In my humble opinion, if 2" makes you feel better, put it around the perimeter and then use The Barrier all inside. It will do the job and cost much less and like BOB in E says, alot less labor. And you can walk on it without damage. There's a lot less seal surface then board as well. |
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NRT.Rob
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Posts:384
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| 03/04/2008 6:39 PM |
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You don't lose 50% of your insulation mass walking on it, irregardless NOFP's claims to contrary.
Labor is less, no doubt. That's not my primary concern in valuable attributes of insulation, however... R value is. Labor is a concern, but not at the expense of R value.
Most hydronics are not designed for "R5", they are designed for whatever gets put in the ground ;)
2" on the perimeter of a slab on grade and a slab edge are very important; there is a lot of loss there, that's not a "if it feels better" issue, that's a direct payback question.
In a buried basement, it's *less* important, though ground conditions count for a lot too and is the X factor that pollutes any discussion of slab insulation. What works over dry sand stinks over wet clay and a wet ground basement can have a much higher heat load than a dry sandy slab on grade. |
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warmsmeallup
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Posts:83
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| 03/04/2008 8:15 PM |
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NRT. All good points. But I don't think it is at the expense of R when you apply what fits the application instead of wasting nonrecoverable funds on what might very well be overkill. I absolutely agree that "what's in the ground" should dictate what we use for R. But saying that there's a typical R value under all heated slabs ..... It is easy, but it's not correct application of our clients' funds.
Bob, I agree with maintaining a static temp throughout. |
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NRT.Rob
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Posts:384
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| 03/04/2008 9:19 PM |
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The vast majority of heated slabs in heating climates in this country should have an R10 under them. While there are exceptions in california and nevada, most other areas of the country have soil conditions that would benefit from more R value. Slab not heated? Dry soil with no risk of ever changing? Large slab centers? Snowmelt? These are all places where the barrier shines. Heated slabs? Most people's jobsites in areas where they will have heated slabs? Use full thickness insulation. Especially on edges and perimeters of slab on grade.
Just because something installs faster shouldn't wash out it's effectiveness.. especially not in today's day and age.
If people want to get full soil studies done and determine the conductivity of their jobsites, then maybe we can get more fully into "custom tailored" advice. Until then, the typical R value is there for a pretty good reason. Can't do R10? R5 is still twice as good as R 2.5.
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yoda
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Posts:4
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| 03/05/2008 1:58 PM |
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Bob,
You should first put down a 6 mil poly barrier then the 2" foam. Keep loops in the center of the slab (2 inches up from bottom). My uncle did his garage and received great info from Houseneeds.
Hope this helps |
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Don Regan
Registered Users
Posts:11
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| 03/07/2008 6:38 AM |
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| This is a much easier way to install Radiant heat with a true R-10 Vapar barrier and tube holder all in one. please check out this site www.crete-heat.com. |
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Farmboy
Registered Users
Posts:150
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| 03/07/2008 11:47 AM |
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| D.Regan. This puts the tubing at the bottom of the slab. Pros..less chance of cutting with saw or screws, puts reinforcement closer to where it should be rather than at the bottom of the slab. Cons..longer heating response time (not that radiant can be made immediate), most of what I've read says tubing should be more to the middle of the slab. |
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Don Regan
Registered Users
Posts:11
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| 03/07/2008 12:13 PM |
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| Please describe your procedure and time involved to keep that tube consistantly in the middle. No matter the location of the tube, the concrete gets warmed to the same temp. Using outdoor reset your slab temp. should remain constant. What your describing only happens on initial seasonal start up and is minimal. |
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NRT.Rob
Registered Users
Posts:384
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| 03/07/2008 12:15 PM |
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siggy showed how tubing at the bottom does require slightly higher water temps and results in slightly higher loss.
Both effects are small. Present, for purists, but not gigantic mistakes. |
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