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Raycore - is it the product for me?

I was pretty much on board with buying Raycore for the 4500 s.f. home I am building in downstate NY, which is steel framed, so I actually don't need any structural value out of the exterior walls other than for supporting the windows and doors (and supporting the walls themselves). I am also going with a wire lathe and stucco on the exterior - Raycore told me I could direct apply the wire lathe and did not have to use any sheathing if I did not need the shear strength, but I am hesitant to do so.

After reading all of these comments, I don't think Raycore is a smart idea as the R-value I would attain for a 5.5" wall doesn't seem worth it to me for the cost of $6/s.f.

I was thinking of just staggering two rows of 2x4 timber stick-built walls back-to-back, with 2' wide, 3 1/2" thick rigid polyurethane foam in between, so that I eliminate the thermal bridging, similar to what Raycore offers (with obviously not as good a seal at the 2x4's, but I would look to spray along the edges by hand). Would this achieve close to R-35?

Would I bond them together with adhesive? Vapor barrier/foil between? Or perhaps go 3" and 3" with 1" furring between to give an air pocket between (would give me a chase for wiring too that way)?


Asked by Joe McCarthy
Posted Jul 14, 2014 6:10 PM ET
Edited Jul 15, 2014 1:39 PM ET


15 Answers

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If you want to build a double-stud wall -- and it's not a bad idea -- the best insulation to use is dense-packed cellulose. Skip the rigid foam layer. You'll get better performance at lower cost with cellulose.

Answered by Martin Holladay
Posted Jul 14, 2014 7:21 PM ET
Edited Jul 15, 2014 1:39 PM ET.


Raycore is real close to dishonest in their r value claims. Polyurethane foam does begin life with an r value of 7/" but as it ages the r value declines. Most reputable polyurethane vendors use r 6/" as an aged value. However it can age below even that value and ultimately be no better than EPS. The second issue with the Raycore claim is that they have wood studs in all their panels and these drop the effective r value as well. using r6/" and 24" OC studs and ignoring top and bottom plates the 5 1/2" Raycore panel is r27 or less not the r35 you mentioned. An 8 foot wall with a top and bottom plate is just over r24, even worse. If you want r35 you'll need a thicker wall and if you are going thicker there are much less expensive site built alternatives. However if your goal is to simply have the performance of the Raycore panels and a 5 1/2" wall a 2x4 24" OC wall with mineral wool bats and 2" of continuous XPS is real close (r22.7 for the 8 foot example) A 6"thick wall again 2x424" OC filled with mineral wool bats with 2 1/2" continuous XPS will outperform the Raycore 5 1/2" wall.

Answered by Jerry Liebler
Posted Jul 14, 2014 7:46 PM ET
Edited Jul 14, 2014 8:32 PM ET.


Until and unless the rigid polyurethane (or polyurethane SIP) manufacturers will stipulate that only a low global warming potential blowing agent such as HFO1234yf (with a GWP ~4x CO2 ) was used rather than the far more common (really the current standard) HFC245fa, which has a GWP ~1000x CO2. using it at higher R-values is the antithesis of "green" building, and may do more environmental harm over it's lifecycle than the energy use it is offsetting (which varies by energy source too.)

EPS is far lower impact, blown primarily with pentane (~7x CO2), but it's same-polymer sister XPS is blown primarily with HFC134a (~1400x CO2). The higher R/inch you get out of XPS is due to the HFC blowing agent, but most of it (and the enhanced performance) is gone in 50 years, whereas the performance of EPS is comparatively stable over time. At the same density & thickness the thermal performance of EPS & XPS converges to the same R value over time. Where the thickness isn't a huge issue it's generally lower impact, greener, and cheaper to use EPS.

Polyisocyanurate is a first-cousin to polyurethane, but is blown with pentane like EPS. It has a very non-linear derating over temperature, with performance peaking at about 50F mid-foam temp, but falls off a performance cliff at mid-foam temps below 30F. In a sandwich situation with fiber-R on both the exterior and interior side it's wintertime performance will be pretty good in NY location, averaging between R6-R7/inch, and in summer would still deliver ~R6/inch. In cold-climate applications where it is the exterior (and thus colder in winter) layer its performance can be as low or lower than EPS (depending on climate & thickness, and the amount of interior-side fiber R.)

All R-ratings of insulation-only products are the performance at standard ASTM C518 delta-Ts and mid-insulation temp of 75F. EPS & XPS performance monotonically rises at lower temps within the winter ranges you would expect in NY, outperforming their rated-R when the foam is on the exterior side of the assembly in colder climates. This is probably true of rigid polyurethane blown with HFC245fa too but I'm not sure about the derating curves of PU blown with water or HFO1234yf compare to that.

Bottom line, if you're going to use rigid foam, polyiso & EPS, placed appropriately in the stackup are your greenest options. Some day HFO1234yf and it's low-GWP cousins may be used for closed cell polyurethane & XPS, but SFAIK none of the major manufacturers of rigid foam board have gone there yet.

Answered by Dana Dorsett
Posted Jul 16, 2014 11:55 AM ET


Joe, I’m sorry you decided to go another route, but I hope your build went well and you are enjoying your home.

In response to Joe’s concerns about the accuracy of reported R-values: RAYCORE uses a state-of-the-art PU foam system manufactured in a proprietary method that produces a product with exceptional insulation values. RAY-CORE’s product R-values have been tested in a certified lab, utilizing ASTM C518 test methods, and the R-values fully represent the effect of aging on the product’s R-value, citing the long-term thermal resistance value of the product. Documentation can be found on the raycore.com website. RAY-CORE’s R-values are certifiably true.

There is a difference between a product’s R-value and the effective R-value of a completed wall or roof. RAY-CORE, as all insulation manufacturers and other Sandwich Panel SIP manufacturers report the R-value based on the product as it leaves the factory, prior to construction. All building systems will experience some R-value loss through the top and bottom plates and window framing. Walls need lumber to attach to the floor and roof, windows and doors - even sandwich panel SIPs and most use splines. There are steps that can be taken in the build process to minimize this. Design, materials used, framing and sealing practices, etc. during the construction phase, along with general quality of workmanship may have a significant impact, consequently each project will have its own effective or “whole wall” R-value.

RAY-CORE's Effective R-value Vs Others... Using Oak Ridge Laboratories Whole Wall R-value Calculator, a decent build with RAY-CORE’s Traditional 2x6 panel with studs 16” oc, will perform at an effective value of R31.41. That may seem like a significant decrease in R-value, but compared to other 5-1/2” insulated wall assemblies, this RC panel is: 58% better than Closed Cell Spray Foam; 61% better than an EPS Sandwich Panel SIP; 77% better than 2” Closed Cell Flash with 3-1/2” Fiberglass Batt; 81% better than Dense Packed Cellulose; 99% better than Mineral Wool (with 1" foam added). Even 10” EPS Sandwich Panels and 10” Double Stud Cellulose Packed Framed Walls have a lower effective R-value than RAY-CORE. I’m aware of a few builds where 1” of foil faced foam was added to the outside to cover the plates. In just 1 inch this adds 4.38 points to the effective R-value, boosting the RC Panel to 35.79, and 2" would bring it to an R-40. If this isn’t good enough, RAY-CORE does offer a staggered stud panel with a 2” foam thermal break in the panel, at the studs, and the insulation value of that break is about equal to the total between-the-stud R-value of most other traditional 5-1/2” walls. The effective R-value of the staggered-stud panel is 22.5% better than the traditional RAYCORE panel, and adding the additional 1" of foam brings it up to an R42.86.

As far as cost comparisons, it has been my experience that many builders just don't have a really good handle on their costs. Builder or DIY'er, I encourage you to get out your pencil and paper and do a real numbers to numbers comparison. A few reminders: remember that top and bottom plates and framing for around windows and doors are the same whether conventional stick framing or RC. Same with sheathing. There will be some savings on labor when framing the basic wall, as the RC panel system has the studs already in place. If you decide you need to beef up your stick framed wall's R-value, you will have additional materials and labor not required with the RC product. And don't forget, with RC your insulation is complete, so no need to put numbers in for that, materials or labor wise with the RC product. Although I don't have data to substantiate it, we are commonly told by builders and other users that using RAY-CORE SIPs cost less than any other building system of -apples to apples - equal R-value.

Answered by Robert Brusman RAY-CORE SIPs
Posted Apr 22, 2017 3:43 PM ET
Edited Apr 22, 2017 3:51 PM ET.


Robert, looking strictly at cavity plus studs (ignoring top plates, window framing etc.), an R22 mineral wool batt framed 2x6 16" OC should work out to about R20. Adding 1" of EPS (R4) or XPS (R5) brings that up to R24-25. Using industry accepted R6/inch for polyiso, how does a 5.5" RC panel come out 99% better? Just curious.

Answered by Lance Peters
Posted Apr 24, 2017 10:41 AM ET


All that verbiage (responding to a nearly three year old thread, no less!), and no mention of the blowing agentsused for Ray-Core's polyurethane. We can only assume it's the high global warming potential stuff unless given updated information.

Ther are now multiple closed cell polyurethane vendors using HFO1234ze (which has extremely low global warming potential) for ~R7/inch polyurethane foam. It can also be installed in fairly thick lifts (4"+) without quality problems or fire issues. Maybe somebody at Ray-Core who cares will get the memo on that even before HFC245fa is banned in the US for blowing foam...

Until then Ray-Core's polyurethane SIPs are still on the "opposite of green building" product list.

Answered by Dana Dorsett
Posted Apr 24, 2017 5:04 PM ET


Dana, thanks for your comments. To avoid the possibility of misunderstanding, RAY-CORE PU System is not a free-rise spray foam. It is a contained, true high pressure injection moulding system, and is a very different blend from spray foam.

Now, let’s talk HFC-245fa, at least in the case of RAY-CORE’s system and manufacturing process. This data comes from the chemical engineers, speaking specifically of our system… 1-5% of the 245fa escapes during our production process. Once the panels are installed, the loss is very minimal because the foam is completely cured, and most everything is trapped in the foam or by the material put over the panel. If the foam is left undisturbed, maybe another 1-5% loss will occur over the life of the panel.

Let’s try to break down the math here. RAY-CORE PANELS: Our foam contains about 6.4% of HFC-245fa. If we’re conservative and a total of 10% of the 245fa off gases over the lifetime of the foam, then 0.64% (0.0064 lbs) of every 1 lb of foam escapes into the atmosphere. The GWP of 245fa is 1,030 times that of CO2. If 0.0064 lbs of 245fa (or every 1 lb of foam) is equal to 6.59 lbs of CO2 (.0064 x 1,030)… then, for an example, a 2,000 sq ft house with RAY-CORE panels at 6” thick would be (2,000’ x .5’) 1,000 ft3. At a 2.3 pcf density that’s 2,300 lbs of foam. 2,300 lbs of foam is equal to 15,157 lbs of CO2.

YOUR CAR: Let’s compare now to a car. The average CO2 emissions from burning a gallon of gasoline is 19.5 lbs CO2/gallon. The average car has a fuel economy of 21.6 MPG, so driving 1 mile emits 0.9 lbs CO2 per mile. The average driver drives 11,400 miles per year, so that equals emitting 10,260 lbs of CO2.

GWP OF RAY-CORE PANELS COMPARED TO A CAR: So, driving a car for 1.5 years would have the same GWP as a 2,000 sq ft house built with RAY-CORE panels. And that’s the GWP of the LIFETIME of the house!

Finely, my response probably won’t put RC on your side of the “green list”. But, please note all things “green” have been considered, and simply put, in RAY-CORE's case HFO1234ze won’t work. It cannot produce a product with the necessary properties of durability and strength , stability of foam - it shrinks, and high R-value per inch needed in a structural insulated panel. This is why it is not found anywhere in the SIP industry. But there is good news - with the ongoing evolution of blowing agents and promising developments with products such as HMO currently on the horizon, I can assure you more environmentally friendly products are in RAY-CORE’s future.

Answered by Robert Brusman RAY-CORE SIPs
Posted Apr 24, 2017 11:20 PM ET


HFC245fa WILL be going away- hope there's a plan for that!

My current car averages ~55 miles/gallon in real-world use, and my next car will be electric, using only renewable grid sources. Using a generic car is a bad comparison, but it does scale the problem.

Comparing it to the carbon footprint of another insulation/construction method of equivalent thermal performance is more appropriate.

By that standard using their own numbers, just the blowing agent component of building with an ~R30 whole-wall Ray-Core SIP (ignoring the impact of the polymer production & disposal) instead of a 9.5" thick cellulose double studwall (also ~R30 whole-wall) is like setting 527 gallons of gasoline on fire.

Answered by Dana Dorsett
Posted Apr 25, 2017 6:56 AM ET
Edited Apr 25, 2017 7:49 AM ET.


Dana, I appreciate your side of the argument, but instead of comparing the RayCore carbon footprint to a relatively uncommon double-stud with cellulose build, how would it compare to a code built house? Then, assuming the RayCore is more efficient once built, how about comparing the lifetime carbon footprint of both houses?

When we discuss reducing the impact of cars on the environment, the pro-green side never uses a 55 mpg hybrid as a baseline, the average vehicle fuel consumption is used. I think we should do the same when comparing home building techniques. Sure there may be a greener way to do it than RayCore, but is RayCore better than the average? I'm asking the question because I don't know, but I would be interested in knowing.

I'm not defending RayCore, I have no loyalty to them. I just like to see a fair argument. Please note this is coming from someone who is currently planning his own double-stud cellulose home, and who aspires to own an electric car for daily transport. The lifetime average for my 6spd Chevy Cruze Eco isn't 55 mpg, but at 44 mpg isn't too shabby considering my climate. :-)

Answered by Lance Peters
Posted Apr 25, 2017 8:13 AM ET


Comparing the lifecycle footprint of the energy use of a house is complicated, and fraught with large error bars. A code-min house uses more energy than an R30 whole-wall house, but the thermal fraction of that energy could be from #2 oil burned at 85% combustion efficiency, natural gas a 82-97% thermal efficiency, or it could come from the power grid with heat pumps or resistance electricity, from coal fired generators or all-renewables.

If grid-sourced that energy has a rapidly evolving carbon footprint, now that variable output wind & solar are beating new fossil burners on a raw levelized cost basis. Both wind and solar (and batteries too) are on a double-digit percentage learning curve, and what's break-even now will be far cheaper (advantage renewables) well within the lifecycle of a house.

Keep in mind that cellulose insulation is a form of carbon sequestration. By some accounting methods it's net carbon negative, but in my prior post I gave it the equivalent of setting ~0.8 gallons of gas on fire n the comparison with the HFC245fa impact of Ray-Core's 527 gallon impact by rounding down instead of up. (11,400 miles/21.6 mpg= 527.777 gallons.)

There is an arithmetic error though- I used the annual number for mileage whereas Robert stated " ...driving a car for 1.5 years would have the same GWP...".

So the difference is really more like setting 790 gallons of gas on fire, not 527 gallons.

OK so it's ONLY like setting 790 gallons on fire- that's pretty green, right? :-)

Answered by Dana Dorsett
Posted Apr 25, 2017 8:34 AM ET


I completely understand your point. What I'd be interested in knowing is how much gasoline are we setting on fire when building a 2000 sqft code-built home using 5.5" R22 fiberglass and 1.5" of rigid foam insulation (or whatever would roughly approximate the energy performance of a 5.5" RayCore wall). I believe the difference between the two is where we should be making the comparison.

With the wild variation in energy source and consumption efficiency, it would only really make sense to figure out the best case, worst case, and average scenario for energy usage and come up with a worst, best and average break even point, no? Otherwise you could drive yourself mad trying to fit region-specific energy scenarios to different construction methods!

Answered by Lance Peters
Posted Apr 25, 2017 9:32 AM ET


Lance, you ask, " What I'd be interested in knowing is how much gasoline are we setting on fire when building a 2000 sqft code-built home using 5.5" R22 fiberglass and 1.5" of rigid foam insulation (or whatever would roughly approximate the energy performance of a 5.5" RayCore wall)." The answer is that as long as that rigid foam is not XPS (i.e., if it's EPS or polyiso), the embodied emissions are essentially negligible. Ideally I'd be able to quote you specific numbers for that whole wall, but the reason I don't have that is that they are small enough that it's not really important to nail them down. HFC blowing agents have crazy high global warming potential and so any time it's involved, it outweighs the other embodied emissions. It ends up that the really important ones are just the energy consumption of the building and the HFC blowing agents.

By the way, my reaction to the "only 5% will leak out over the life of the panel is "I'm sorry to hear that you expect the life of your panels to be so short. Maybe that's another reason not to buy them."

Answered by Charlie Sullivan
Posted Apr 25, 2017 10:06 AM ET


Lance, if you're interested in doing some back-of-the-envelope calculations, the "Inventory of Carbon and Energy" is a decent resource for finding the embodied energy and embodied carbon of common materials. The spam filter won't let me link it, but you can google it to download a copy. It's a giant excel spreadsheet with tons of sheets full of all sorts of info.

Big caveat: I don't think ICE accounts for the global warming potential of blowing agents in foamed plastics, so you will have to consider that in addition to the embodied energy metrics.

Taking a quick peak at ICE, from an embodied energy point of view (all units in MJ/kg), Cellulose 0.94-3.3 and Rock Wool at 16.8 and Fibreglass at 28 are much more low energy choices than Expanded Polystyrene at 88.6 or Rigid Polyurethane at 101.5.

This is before you account for the tremendously high global warming potential of the blowing agents in XPS, polyurethane foams, etc.

Short answer is that 5.5" of fiberglass + 1.5" of foam is going to be way more low energy than 5.5" of foam, even before you account for the additional problems from high GWP blowing agents.

If you're gonna use foam, the best choice is recycled foam. The next best choice is foam with relatively low GWP blowing agents like EPS and Polyiso. There really is no good reason to use new XPS or Polyurethane blown with high GWP blowing agents, especially considering all the alternative options available these days.

Answered by Brendan Albano
Posted Apr 25, 2017 10:27 AM ET
Edited Apr 25, 2017 10:31 AM ET.


You can burn a 2000' 2x6/R22 + 1.5" polyiso overcoat house to the ground and it still might not hit the same greenhouse gas emissions of setting 790 gallons of gasoline on fire. (Think of a 3 x 5 array of 50 gallon drums of gasoline- that's quite a volume of high carbon density hydrocarbon!) It might be close if you're using 1.5" of HFC134a blown XPS for the 1.5" foam-over (due to the higher GWP of HFC134a.)

Getting rid of the HFC245fa it will bring polyurethane core SIPs down to the same order of magnitude of lifecycle emissions of conventional building, but it still has a high polymer per R content making it considerably less green than a half-pound open cell polyurethane double-studwall approach to hitting comparable performance points, which is still higher than cellulose.

If the current administration guts EPA or curtails any new regulation on HFC use as blowing agents it may take awhile for HFC245fa to go away, but it would be silly at best to assume that they'll be in use for the foreseeable future- it really IS going away, it's only a matte of when, and Poly-Core is well advised to be working on a low GWP next generation, which will both move the product a long way toward the green zone, and give them a better shot at a long term future. SIPs have many advantages over stick-built (ease of air sealing, speed of assembly, etc) .

If as 95% of the HFC245fa is retained at end of lifecycle, the disposal methodology of the PU-SIP is absolutely CRITICAL to it's ultimate impact.

EPS core SIP foam is blown with pentane, which has a much lower impact even if released. Most of he pentane is released during the manufacturing process, and in most EPS blowing operations the lions share of that is recovered (to meet local air pollution standards), often burned for process heat, displacing other fuels for that heat. Polystyrene feedstocks have a different footprint from those used for polyurethane & polyisocyanurate (which are very similar to each other), but those differences are small in comparison to the blowing agent issue.

Hopefully we can look forward to Ray-Core's press release on the launch of their new low-impact product in the near future (and the retirement of their HFC245fa blown goods)!

Answered by Dana Dorsett
Posted Apr 25, 2017 11:37 AM ET


Charlie, Brendan, Dana, thanks for the insight.

Answered by Lance Peters
Posted Apr 26, 2017 8:46 AM ET

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