Is anyone familiar with this product? It's eps with polymeric facers on both sides for strength.

I've seen it. While it turns the EPS into a better air barrier, it also reduces vapor transmission/ability to dry.

So, as a sheathing layer the facers are problematic?

Probably not, but more drying is usually a plus. EPS with a durable, highly breathable, easily taped, adhered air barrier film would be interesting, but I haven't seen it.

I can't tell you how frustrating this has been. My timberframe is complete, light frame built and I can't find an insulation supplier - other than lowes- that carries eps sheets. Trying to avoid xps because of the gwp warnings but I need to button up before snow.

try looking for a company that makes packaging material, thats how I stumbled across my eps supplier. A couple emails and suddenly I can get any type eps, any thickness, shower preslope pans, shower benches, shower niches, attic access plugs, all at competitive prices just down the road. I pick it up right from their plant, and had no idea they could do the construction products for the past 13 years until i picked up the phone and asked.

I noticed you posted on Greenbuildingadvisor with addtl info that you're going to have only foamboard sheathing with a cellulose densepack, you might run into problems densepacking against foamboard and getting the density you need without cracking or outright snapping the foamboard.

I would use a higher density eps, at the very least its going to bow out between studs, if your strapping studs for a rainscreen that will help alot from the sheet blowing off the wall. An alternative is a fiberglass dense pack, less than half the density of cellulose.

In his location with 5.0" of cellulose it needs to be at least R10 for dew point control, which takes 2.5" of EPS. With Type-I EPS it still might bow a bit even with the facers, but it wouldn't break. But Type-II is plenty stiff enough to dense pack against at 2.5". After all, 2.5" of Type-II EPS is good enough to hold back the concrete in insulated concrete forms at reasonably wide reinforcement spacings.

Reclaimed XPS is greener than virgin stock EPS, at any density. On GBA I pointed him to a reclaimer about 90 minutes away that is advertising a stockpile of used 2.5" XPS at a price lower than 2.5" of Type-I EPS. At outdoor temperatures that matter from a dew point control perspective, 2.5" of XPS or Type-II EPS is well north of R11, and more than adequate for dew point control on 5" of cellulose.

With 2.5" thick sheets I would be putting up one layer and wonder how critical it is to have multiple layers with the ability to stagger seams. I'm unfamiliar with adhesives that work well with unfaced foam. Would detailing that aspect for a tight finish be possible?

Dana,
Icf has form ties holding both sides together keeping it from spreading, foam attached to studs doesnt enjoy that benefit although exterior strapping will help exponentially. Concrete slumps in slow even pressure, dense packing loads pressure in a smaller footprint around the nozzle, the surrounding insulation only concentrates the pressure, even with the netting. I just handled 2000 sf of type ii for an underslab and you could definately snap that if you got careless with a big blower. Type ix gets quite a bit stiffer from type ii.

My krendl can come over to your house and easily blow the drywall or plaster off your wall, it can also blow and or crack foamboard with insulweb on the other side. Im not saying it will, im saying it can and I've seen it and Ive done it when ive pushed density too far against 25 psi xps, polyiso, as well as a variety of other materials. FYI, ive also cracked plaster, popped drywall, blown mesh out of the staples, broke open band joist bags, snapped ceiling tile (huge mess) among other infractions. Most of these were retrofits where you are going by feel and cant see, only hear whats actually happening, some were open bays with myself actually watching the failure so Im not saying it cant be done, but your stackup isnt a sure bet with cellulose.

So to the OP, get a good installer, and slow and steady wins the race. If you cant get density, you have a real big problem.

Posted By greentree on 21 Sep 2016 10:39 PM
So to the OP, get a good installer, and slow and steady wins the race. If you cant get density, you have a real big problem.

That's a whole other topic of greater concern than anything else I've had to consider. Every aspect of this build has literally been in my hands so there's been no compromise or having to look over the shoulder of a hire. Every insulation contractor I've had out to bid the job primarily advertises for and advocates and pushes for sprayfoam. The response to my request for cellulose has unequivocally been (and on a couple occasions only after a brief argument when I have to insist I want cellulose and not foam), "oh yeah, we can do that too if you want". When I ask what product they use and if it's all borate I get a blank look. No idea what they're using. If I'd of known this when I stated this project I would have gone out and gotten trained to spray cellulose myself.

Damp spray may work for you without the dangers of dense pack.