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Community and Q&A

New house build, SIPs?

lance_p | Posted in Green Products and Materials on

New member here, we are planning to build a new house this summer and I’m exploring my options for wall systems. I plan to do the framing myself. House will be roughly 2500 sqft in Ottawa, Ontario Canada. Not the coldest place to build but not far off, and just for kicks it gets pretty hot and fairly humid here in summer as well.

I’m weighing my options as far as wall construction goes. I would like to build as much insulation into my walls and ceiling as is practical, targeting a cavity value of around R40 seems like a good goal, and a reasonable effort to minimize thermal bridging for good whole wall performance.

I’ve been thinking about a double stud wall and was leaning that way fairly strongly until I came across Raycore SIPs. I like the idea of having studs, and they make a version of their 5.5″ wall with offset 2×4 studs which should help significantly with the thermal bridging issue.

My question to the experts here: is this Raycore system worthy of a truly efficient build? Has anyone here used this system before? Are there other similar systems available?

My searching hasn’t turned up anything else besides the typical OSB/foam “sandwich” type panels, and I’m not sure I’d want to trust the OSB-to-foam bond for structural walls.

Thoughts? Looking for all the input I can get. The double-stud approach would likely be cheaper, but I will be doing this myself so simplified construction will be worth something as well. Thanks!

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  1. charlie_sullivan | | #1

    There are two big drawbacks of Raycore panels:

    1) The embedded studs result in thermal bridging. It looks like some of the thicker walls have staggered studs which reduces that effect, but it doesn't eliminate it, and the fact that their web site glosses over that fact kind of ruins their credibility in my book.

    2) They use foam made with a high global warming potential blowing agent. If part of your goal in building efficiently is to reduce climate impact, this will undermine that effort.

    If you are deciding between double-stud cellulose vs. SIPs, consider I'm not sure how much trouble it would be to deliver them to you though.

  2. user-2310254 | | #2

    They also seem to inflate the r-value of the closed cell foam used in their assembly.

  3. ohioandy | | #3

    Lance, speaking as someone who built a SIP house with a skeleton crew, just know that anything assembled with individual sticks is a simpler method. But there's something inarguably elegant about the totally studless (and therefore thermal bridgeless) panels, which are more than capable of bearing structural loads. With thicker panels comes more rigidity and increased carrying capacity. Most SIP manufacturers will generate a detailed set of stamped engineered drawings, whether you're cladding a timberframe or using panels as the structure. Presumably, they will also find or provide a skilled crew to assemble the thing, if that's in your budget.

    Well-grounded concerns persist on this site and elsewhere, but if your supplier is responsive to your questions and your installer is experienced, SIPs are legit. Whether you can find a responsive supplier and an experienced installer in your area, that's another matter!

  4. charlie_sullivan | | #4

    I just remembered a similar system, EZ-SIPS:

    Those are EPS panels slotted for studs. EPS is a lot more environmentally friendly than HFC-blown polyurethane. I would expect them to be cheaper than Raycor, and the R-value will be more stable long term.

    Still, I'm not sure I get why one would prefer them to filling a stud wall with cellulose. I think they have been discussed here before.

  5. drewintoledo | | #5

    Raycore looks like a neat product. I'm curious - how would one insulate the top and bottom plates?

  6. Dana1 | | #6

    Drew- until & unless Raycore starts using polyurethane blown with a much lower environmental impact such as HFO1234yf or H2O they're off my personal "green" list, (in fact it's in the other column.) The same performance can be had with a EPS core SIP at much lower impact without a gia-normously greater thickness. The raw amount of polymer per/R alone puts 2lb or denser polyurethane at the least-green end of the scale, to be used judiciously, only when necessary, and the HFC245fa blowing agent moves it off the end of that scale. When used for adjusting vapor permeance or for it's waterproof characteristic there are locations where some amount can be rationalized (say, retrofit insulation & air sealing of stone foundations). But making it the primary insulation material in a high-R assembly has negative environmental consequences that may never make it back to break-even on the avoided environmental impact of the energy use saved.

    This is in stark contrast to half-pound density sprayed polyurethane, which uses about half the polymer per R, and is blown with water. Half-pound polyurethane is arguably the greenest version of foam insulation in common use.

    All SIPs suffer the thermal bridging issues at the top & bottom plates, and at the window & door framing, as well as the internal structural splines/studs. It's an expensive way to build when going for high performance. The advantages are that it goes up very quickly and it's easier to air seal rather than stick-built construction, but the higher cost per whole-wall-R (=all thermal bridging accounted for) only becomes financially rational in high labor markets or situations where calendar-time-is-money.

  7. user-6179224 | | #7

    With respect for those who have posted regarding RAY-CORE Structural Insulated Panels, I will try to respond to unanswered questions and address concerns with accurate, informative and useful information, hopefully without giving too much of a “sales pitch”.

    Lance - Regarding the cost of double wall construction vs. RAY-CORE SIPs? We have no data to substantiate it, but we are commonly told by builders and other users that using RAY-CORE SIPs cost less than any other building system of equal R-value. Comparing apples to apples, we know that RAY-CORE is the least expensive per R-value inch SIP on the market… ok, sounds like a sales pitch, so compare.

    Charlie shares a good point - All building systems have some thermal bridging. Walls need lumber to attach to the floor and roof, windows and doors - even sandwich panel SIPs and most use splines. Drew asked about insulating the top and bottom plates. It seems that most do nothing, but I know of a few that added 1” of foamboard to the exterior as a thermal break. RAY-CORE does offer a staggered stud panel with a 2” foam thermal break at the studs and the insulation value of that break is about equal to total between-the-stud R-value of most other traditional 5-1/2” walls. Visit to learn more about this staggered stud panel.

    Talking 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 website. RAY-CORE’s R-values are certifiably true.

    The “hot” topic… polyurethane foams and their blowing agents. We get it. Reducing the long-term environmental effects of RAY-CORE products, components and processes are at the very top of our initiative. To educate those that don’t know… HFC-245fa is not classified as a “volatile organic compound”, and is “non-ozone depleting”, regarded as “environmentally friendly” under US Regulations. BUT, it is a global warming gas with a global warming potential. Not where RC wants be, but with time we will get there. If it’s any comfort, in the production process the HFC-245fa is trapped in the panel’s closed cell foam for the life of the structure. This is what makes it a superior insulation. Reducing a structure’s energy consumption directly reduces the global warming effects of CO2 emissions.

    Thank you Dana for weighing in, your knowledgeable comments and opinions are well received and I know my response won’t move RC onto your “green list”. But, please note all things “green” have been considered, and simply put, in RAY-CORE's case these products won’t work. The suggested blowing agents and density reduction cannot produce a product with the necessary properties of durability and strength (requires high density), stability of foam (it shrinks) and high R-value per inch (water based is about ½ the R-value) needed in a structural insulated panel. This is why they are 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 products are in RAY-CORE’s future.

  8. lance_p | | #8

    Hi Robert, thanks for your follow up.

    Given our budget, location (Canada) and insulation level goals, I'm leaning strongly towards the double stud with cellulose method for now. The current exchange rate plus freight from the US are two strong factors in my personal scenario which may not affect others, but even excluding those our budget would not allow for the SIP build.

    The greenhouse gas consideration is also part of it, and I was able to find a local supplier of cellulose insulation. Using what is mostly recycled local content to insulate our house has a good feeling to it.

    Thanks again.

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