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Rigid foam insulation

We are doing rigid foam on 4500 sq. ft. of exterior walls at 4" thick and 4500 sq. ft. of roof at 8" thick in a REMOTE application.

We are attempting to find the best value for our exterior foam insulation.

So far the best value ($26 for 2"x4'x8') we could find was NeoPro TK. Seems to be a new product so not a lot of info on this "revolutionary" new material. http://www.permarproducts.com/insulsheathing.html

Our previous first choice was Foamular 250 http://www.foamular.com/foam/products/foamular-250.aspx, until we started getting quotes ($34 for 2"x4'8').

PolyISO is out at this point due to it's fluctuating R Values and our need for some below grade applications.

Can anyone recommend any other products?


Asked by Eric Burhop
Posted Aug 20, 2014 10:44 AM ET
Edited Aug 20, 2014 12:29 PM ET


8 Answers

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Double post

Answered by stephen sheehy
Posted Aug 20, 2014 11:18 AM ET
Edited Aug 20, 2014 1:54 PM ET.


Can you give me the information for your supplier?


Answered by Eric Burhop
Posted Aug 20, 2014 12:29 PM ET


Eric- I'm getting it from


They're near Worcester MA. Ron Gluck is the guy I've been dealing with:

Green Insulation Group

Answered by stephen sheehy
Posted Aug 20, 2014 2:04 PM ET


Graphite EPS has been around for about a decade or so now, and seems to be a pretty good product. EPS is blown with pentane which has a fairly low environmental footprint, and a global warming potential of about 7x C02.

Foamular 250 is blown with a mixture of HFCs, the predominant of which is HFC134a, with a global warming potential of ~1400x CO2. Worse still, as the blowing agent leaks out over the next 50-75 years it's thermal performance drops to less than that of the graphite loaded EPS at any given thickness.

Polyiso can be pretty good if it's the interior side 1/2-2/3 of the foam thickness, since it will stay in it's high-R range, well below the knee where it's performance drops off a cliff. For a 4" thickness in US climates zones 5 and up you'll get better performance out of 2" polyiso + 2" graphite loaded EPS than with 4" of either.

The NeoPro is a bit on the low-density side for use under slabs (1.15lbs per cubic foot, rated 13 psi ). It'll be OK in most residential slabs, but some local codes may demand higher compression ratings. When using lower-density foam don't skimp on concrete thickness or slab reinforcement- the more rigid the slab, the better the dynamic loads get distributed. But since space/thickness isn't at a premium under slabs, using standard Type-II or Type-IX EPS (no graphite loading) there might be cheaper.

Of course, reclaimed/recycled foam board is both cheaper and greener than any of the above. These folks have distribution over most o the US, but there are often local smaller-scale competitors: http://www.nationwidefoam.com/

Answered by Dana Dorsett
Posted Aug 20, 2014 2:13 PM ET


If you are going to use plain ole eps, these guys: http://univfoam.com/ quoted me a lower price for 1.5 lb 3-3/4" 4x8 sheets than your best price for 2" thick

Answered by Trevor Chadwick
Posted Aug 20, 2014 7:08 PM ET
Edited Aug 20, 2014 7:43 PM ET.


Thank you everyone for the thorough responses.

The prices I have been quoted in the last day have alleviated a healthy chunk of our budget concerns (insulation budget is down to 50% of the original).

Can anyone speak on the R Values one could expect from reclaimed XPS or Polyiso? (Mr. Dorsett?) From what I read, polyiso loses performance at lower temperatures, however, the actual characteristics of the material itself have not permanently changed from being at cold temps?

On a similar note, is reclaimed XPS or EPS still structurally sound enough to use underslab or is there a chance it has permanently degraded?

Answered by Eric Burhop
Posted Aug 21, 2014 7:28 AM ET


For what it's worth, I just received delivery of recycled xps for under my slab. Other than being dirty, it looks like new foam. Edges are square, only a few minor dents. I'm quite pleased at the quality.

Answered by stephen sheehy
Posted Aug 21, 2014 3:28 PM ET


Polyiso performace slips off a cliff when the average temp through the foam drops below 40F, but isn't damaged by the cold- when temps rise it comes right back. The ASTM C518 testing used for labeling any of this stuff is at an average temp of 75F, but polyiso's performance improves substantially, peaking at about R7/inch center-foam temp is about 60F (say 50F outdoors, 70F indoors, no other insulating layers.)

But it then begins to fall pretty dramatically with falling temp. At a center-foam temp of 45F it's running about R 4.5/inch, at a center foam temp of 25F you're looking at maybe R3/inch.

XPS loses R value monotonically over time, eventually reaching EPS performance when the densities are equal. So assume 1.5lb XPS will eventually perform at about R4.2/inch, depending on how long it has been in service, whereas 2lb XPS will be more like R4.3/inch.

Unlike polyiso, polystyrene performance continues to improve linearly with fallling temp well into negative digits. At a center-foam temp of +25F you can count on about R4.7/inch, even when fully depleted of it's blowing agents. At +40F mid-foam temp it'll be about R4.5/inch.

In REMOTE stackups you can get better overall performance at a given foam thickness by making the outer layers polystyrene, the inner layers polyiso. As long as the average mid-winter temp at the EPS/polyiso boundary is above about 40F it means the polyiso layer willl be averaging near it's optimal temperature, and the outer layer of EPS would outperform polyiso. A comparative view of the derating curves (looking at conductivity or 1/R) can be found here:


Compressive strength of foamed polystyrene foam does not degrade appreciably over time unless it's been left literally for YEARS exposed to direct sunlight (where the UV breaks down the polymer). If it's not all chalky on the surface and fully bleached out, it's pretty much good to go for sub-slab applications (even if it IS all bleached out & chalky it's probably still good enough from a compressive point of view, but may have a higher than desirable open cell fraction.) Density is pretty much the determinant of how well it will do from a compressive strength point of view. Almost all XPS sold is 1.5lbs density or higher, most EPS used in construction is 1.25lbs (Type-VIII) or higher. Perhaps the most common density used in construction is 1.5lbs (Type-II).

Answered by Dana Dorsett
Posted Aug 21, 2014 4:55 PM ET

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