Enercept 16 inch structural insulated roofing panel

16" SIP

I just took delivery of a 16″ SIP panel sample piece courtesy of Enercept. As you can see in the picture, the sample includes a TJI spine—this piece came off a run they did for a roofing job. Enercept offers thermally broken studs for wall panels as well as the pictured TJIs. They claim that the EPS foam is made largely from recycled content. I am looking to verify that.

The seam tape is labeled as Ashland’s Structural Insulated Panel (SIP) Sealing Tape, a  patented, pressure-sensitive, vulcanized butyl rubber adhesive laminated to a polyolefin carrier membrane. This sort of product is of interest not only to SIP construction but would be useful for any wall assembly that utilizes OSB as an air tightness and/or vapor retarder.

What is the relevance of a 16 inch SIP, you may ask? Well, it turns out that for Passive House walls in Minnesota climate, this panel provides nearly adequate R-value. For those not familiar with the term, SIP stands for “structural insulated panel” and basically describes a sandwich product that can be used for building envelopes: floors, walls, and ceilings/roofs.

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  • Charles says:

    ICS-RM (www.ics-rm.com) can provide an 8in PUR panel exceeding R56 in insulation value at 1/2 the thickness. AND there are no thermal wicks in the entire envelope. The above SIP will have more than 32sqft of thermal wicking across even a small house. EPS is a thermoplastic – it can be melted and reformed, though there are almost no industrial scale recyclers in the US. But this same property of melting (at low temps) makes it illegal or cost prohibitive (much higher insurance) in Europe and Australia. There 90% of the construction panels sold are of PUR. There are as many people recycling PUR as do EPS – not many. But I believe the best use of a petroleum product is a permanent one and both products will survive for millenia (except PUR that degrades over time when exposed to UV light).

  • Tim Eian says:

    Thanks for the comment, Charles. I believe that EPS has less embodied energy than polyurethane (PU), and that is something that appeals to me as a designer. EPS is highly recyclable, too. I would need to do more research to do an apples to apples comparison of the stats on both EPS and PU. If you, or someone who reads this post has that available, please post it to this blog.
    Just FYI, the panel pictured delivers close to R-60. For a current design I am looking for about R-70 to R-75, so the interior of the panels will be furred in with 2×2 or 2×3 strips to allow for electrical, as well as another layer of PU insulation. The interior OSB sheathing will become the air tightness and vapor retarder layer of the assembly.

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