Bigrhamr
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| 05/20/2009 1:28 AM |
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Does anybody know about R-Tech Insulfoam sold at Home Depot? It's substantially cheaper than the Owens Corning 250 but there doesn't seem to be much info on it (like compressive strength) They say "Yup, it's good for under slab on grade" but nobody seems to know a psi rating.
Are there any definitive answers out there regarding how much compressive strength is needed? Most recomendations seem to be for 25psi
under shop floors, would the 15 psi stuff like Owens Corning 150 be suitable for a floor that just sees foot traffic?
Application is 5" thick slab on grade with radiant heat, part will see moderate forklift use and part is just office space.
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BadgerBoilerMN
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| 05/20/2009 6:51 AM |
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250 would be marginal for commercial applications of any kind. If you go to the OC website all will be revealed. Or you can take the advice of the Home Depot team...
A good percentage of my work is repairing "big box inspired" radiant floor heating systems. |
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MA
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Mungo Park
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| 05/24/2009 10:42 PM |
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Thanks for the help, I was looking at the same issue.
Cheers Ron
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BadgerBoilerMN
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| 05/25/2009 12:27 PM |
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| A little bit of design help up front can save many dollars after the fact. Is there anything you've missed? |
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MA
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NHgreen Builder
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| 05/26/2009 1:53 PM |
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| Before you go to home depot please check out P2000. It is arguably the best Radiant barrier/ Rigid insulation On the Market today. Their website should give you any info you need. Its prices are competitive to the home depot radient barrier. but your energy savings will be much higher. I am an independant sales rep for the New England master distributor. Feel free to E-mail me at benainslie@hotmail.com with any direct questions. |
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NRT.Rob
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| 05/26/2009 1:57 PM |
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| P2000? wow. What's the R-value ben? |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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NHgreen Builder
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| 05/26/2009 2:10 PM |
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| Under a radient floor P2000 is R-4 (per inch) according to Astm:518. I know we live in an R-value culture but I challange anyone reading this to think outside the box. P2000 performs at a much higher level than what Guarded Hot Box R-testing tells us. A new test ASTM-c1363 which tests the product within a wall system used by the ICC gave it an R-10.2. The ICC put R-19 fiberglass into the identical wall system and it only had an R rating of 11! All this proves is there is more to insulation than R-value as set by todays standard testing. The real proof of a insulation's worth is its' satisfied customers. As this started with the question of strength. All EPS boards are strong enough to go under a slab. Infact because of how the weight is dispersed a concrete slab has less weight per inch than a grown man. |
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NRT.Rob
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| 05/26/2009 2:25 PM |
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we are talking about a slab. Under a slab, it's about R value, and only R-value. Your arguments about fiberglass may or may not be true in a wall assembly, but they are patently false under a slab, and many reflective foil companies have been sued in the US for violating the FTC's "R value rule" for the same language you're using now. When you sell insulation, you sell it with an R-value and you are forbidden by law from making side claims that have no basis in fact.
You now have ASTM ratings for whole wall assemblies, as you note. Use them, for the assemblies they are testing.
The Real proof of an insulation's worth under a slab is its R-value. Not testimonials by laymen, not handwaving about fiberglass or "thinking outside the box". R-value.
Under a slab, this is just EPS of an equivalent thickness. and that is generally a substandard thickness (less than 1"). Therefor, while better than reflective foil under a slab, it should still not be used. Thicker EPS or XPS should be. |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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BadgerBoilerMN
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| 05/26/2009 2:51 PM |
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More snake oil. Always someone trying to prove "there's a sucker born every minute".
Radiant barriers are for walls, ceiling and space ships but never under radiant floor concrete slabs!
If you want to waste money, buy a lottery ticket. |
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MA
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NHgreen Builder
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| 05/26/2009 3:32 PM |
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Everything I stated before applies to FTC rules for R-value statements (16CFR460) see www.ftc.gov/bcp/rulemaking/rvalue/16cfr460.shtm as a rep for an insulation product i know exactly what I can and cannot say. As I said before P2000 is r-4 per inch under the ASTM-c518. As is all EPS as specified by LEED.
The thought that a radiant barrier does not belong under radiant heated slabs baffles me. Till now I thought it was universally accepted that Radiant barriers are the single best thing to put under a slab. |
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BadgerBoilerMN
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| 05/26/2009 3:40 PM |
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| You would not pass the RPA designer certification (nor a basic course in thermodynamics I suspect) but yours is not a new position for salespeople. It is nearly a full time job, keeping the novice from misguided (or self-serving) Internet bandits, as Rob will attest. |
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MA
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NRT.Rob
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| 05/26/2009 3:42 PM |
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Then you have learned something new. There is no opportunity for radiant heat transfer under a slab, because there is no airspace. it's purely conduction, and therefore only conductive heat transfer resistance matters. I would hope a rep for an insulation product would know the basics of heat transfer, but then, the ones that rep radiant barrier products seem to forget that awful quickly and on a regular basis.
If you want to discuss wall insulation, you have more of a leg to stand on... but that's a separate thread. This one is about slabs.
I need to back up a bit though, you guys have a 1" thickness you didn't have the last time I checked. That is starting to get into a decent amount of insulation. It's still half of what is normally specified under a slab, but it's better than a quarter at least. |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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jonr
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| 05/26/2009 6:39 PM |
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Maybe a simple test is needed to demonstrate this. A couple of heat lamps shining on concrete/test insulation/sand sandwiches. Put thermometers in the sand and see which one heats up quicker.
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BadgerBoilerMN
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| 05/26/2009 6:44 PM |
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| Riiiiight. We have enough pedants on this blog already. |
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MA
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BillN
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| 05/26/2009 10:11 PM |
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lots of chatter about insulation, but take a step back. This is a commercial slab with fork traffic.
The wonderfull radiant slab will be getting replaced if the normal fork truck traffic can bust it up.
The ACI sites 4 different design methods for slabs on grade, one of which is a design for fork truck traffic. Variables include axle load, type of tire, # of tires, tire contact area, and subgrade modulus. In this case, the subgrade is composed of the actual subgrade, plus the insulation.
Without getting into specifics, I can tell you that the less bearing capacity of the insulation, the softer it will be. Imagine stepping on a piece of cardboard which is laying on a mattress. Then step on another piece of cardboard which was placed on compacted gravel. The response of the cardboard (slab) will be much different.
So, the softer the subgrade, the thicker the slab has to be, AND the more steel has to be in it.
I have done designs for radiant heat slabs in freezer warehouses (i know this is counter intuitive). If i remember correctly we were typically doing 8" thick, 4000 psi, 30 ft joint spacing, 0.3% steel.
As for insulation on this project, I recomend the minimum of the most rigid type. |
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dmaceld
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| 05/26/2009 11:42 PM |
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Posted By NHgreen Builder on 05/26/2009 3:32 PM
The thought that a radiant barrier does not belong under radiant heated slabs baffles me. Till now I thought it was universally accepted that Radiant barriers are the single best thing to put under a slab.
Uh, you need to study up on how radiant barriers block thermal energy flow. Interestingly, from what I can see you will not find that explanation on the P2000 web site. They are very careful with their wording. They throw around radiant barrier and blocking all three types of heat flow with no explanation how the product does it. In fact, I don't think it says flat out anywhere that P2000 blocks heat flow due to its radiant barrier foil coating when installed under concrete.
P2000 performance is implied, not explained.
Hint: reflection and emissivity, reciprocals of each other, depend on the existence of a gap.
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Building house - what a way to spend retirement! It's done! We're living in it! |
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BillN
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| 05/27/2009 6:47 AM |
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right !
ignore the sales pitch and understand the basics. From what I remember in thermo, energy travels in 3 ways, conduction, convection, and radiation.
If there is no air, or gap, the last 2 drop out. |
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NHgreen Builder
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| 05/29/2009 9:39 AM |
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| The tensile stength of the P2000 product is MD17,000 psi\TD 30,000 psi, Which is more than substantial for this project. I think as far as the arguement of a radiant barrier's usefulness under a radiant slab I agree your every day Aluminum faced radiant barrier is completely useless under a radiant slab. Everyone seems to be assuming this product also has a foil face which we all know cunducts heat tranfer without an air barrier. The single best thing going for P2000 is its reflective facing is a Metallized plastic often referred to by the "Brand" name Mylar. The great thing about this is it does not need an air gap to stop heat transfer because it is non conductive of any kind of energy, but don't take my word for it just ask Nasa or your local Fire Chief. |
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ecobuilder
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jonr
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| 06/04/2009 8:28 AM |
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> Mylar. The great thing
about this is it does not need an air gap to stop heat transfer because
it is non conductive of any kind of energy
Snake oil.
Also be careful of someone who sells you a .01 inch thick sheet of plastic and says it is R4 *per inch* (hoping you will forget to divide by 100).
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