I am curious as to how sip roofs meet the minimum r value requirements in certain areas. I haven't looked into the sip roofs much, but I don't believe any have an r49. This is the new code requirement for all attic spaces in michigan (as well as other states i believe).  I am curious to hear from some of the sip pro's as to how they meet the requirements for roof applications in these areas.

Thks......Bunt

our 12" steel/EPS -  SIPs are R-51,
it varies from state to state depending on which code they have adopted
R-19 is the minimum requirement in Florida.

In many cases combinations of products will get you there without going to SIPs (in most cases). For example traditional cellulose or fiber (like spider fiber) fill insulation (not batts) combined with a radiant barrier like LP TechShield will yield significantly higher R values than simply the fill insulation alone would and when you're simply covering attic space it doesn't always make sense from an economic perspective to use SIPs. But having a requirement of just under R50 is a challenge and I'd hate to have someone have to put 12" panels all over the roof of their house (sorry but I'm ONLY coming at it from a cosmetic issue - otherwise 12" or even 20" panels are GREAT). It just looks weird to me. Try a combination of insulations and radiant barriers or insulation in the attic deck with insulated panels. Oak Ridge Nat'l Labs is doing a fair bit of research in this arena as a low cost yet effective option. Discuss with the building code officials or if your local colleges have building programs call their faculty. Ask around, the truth will out. Good luck.

Thks for the replies!!

 

Bunt

Another possibility is an XPS 10" R-50 panel.

Jay Shultz
The Murus Company
800-626-8787

Great for Murus. Not many folks out there using XPS these days. I know Murus has a great product - how do the price points compare with PU and EPS?

With higher R values being required in certain parts of the US, choice of foam core becomes the key to building practically with SIPS. A Poly-Urethane foam core is the way to go, if you want to keep the SIP to a managable thickness. A well kown company I know of makes a 6" thick 26ga. steel skinned panel with a 2.4 density PU core that acheives R-54. I'm a SIP designer located in Florida and design homes and additions exclusively with metal SIPS. Metal skinned panels are the way to go in my opinion.

No doubt amoung SIPs on the market today PUR has the best R value per inch, but R-54 in 6"? Do they have data supporting that? Given that typical steel siding is only going to be about 1/8" (combined interior & exterior thicknesses) total we can approximate a full 6" of foam just to make the math easier. That would imply an R9 per inch of PUR foam. I would call that unrealistic but would love to see the supporting data.

Hi CHL,

They could be exaggerating slightly, but they quote a foam density of 2.4 lbs/cu ft, which is pretty high. They have test data, but most know that R-value quoted by itself is an incomplete determination of performance. I'm pretty sure it would be good enough for Michigan. As a designer, if the building department turned my permit down for missing the R-Value, I would then start adding up the drywall, roofing, air films and anything I could to jump the R-value hoop dictated by the building code. Actually, the company is Alumasheild Metecno, and the foam might actually be polyiso. They are based here in Florida where I am.

The pricing for XPS panels have not been finalized, however from what I have seen the price (for comparable R-values) is more than our EPS and close to the price for a Polyurethane panel.

Jay Shultz
The Murus Company
800-626-8787