Generic / unbranded EPS foam insulation
Hi everyone –
Was just in the process of getting quotes for EPS foam for footings and under slab. Prices are all over the place, so I went by a yard of a big material supplier to investigate and found they stock totally unmarked and unbranded 4×8 EPS in 1”, 1.5”, and 2”. I didn’t get much info from the guys in the yard but they said they just delivered a bunch to my area for a new house.
I understand that EPS (Type II vs IV vs XPS) below grade/under slab is a bit contentious, but I was curious if anyone could comment on the importance of rated R-value, brand, etc in terms of longevity and compression strength for type II. Is EPS just EPS? Is 1.0 pcf equivalent to 15 psi? Is it all about R-4 per inch? In your experience, do inspectors want to see a brand and rated R-value or are they more concerned in seeing the specified thickness? And I guess most of all, is it worth saving 50% verses a name brand like insulfoam?
Thanks for the input
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Zane,
If you visited the "yard of a big material supplier," someone working at that business -- a supervisor or manager -- knows where they got the EPS that they are selling. You need to find that responsible employee to learn the name of the EPS manufacturer. Once you have that information, you should be able to track down basic information, including the type of the EPS, as well as its rated R-value.
Building inspectors sometimes care about the labels on the insulation installed between studs or in attics, but I can't imagine that a building inspector will ask too many questions about the rigid foam under your slab. But I would well be wrong on this point, so it never hurts to call up your local building department to get their take on your questions.
Thanks Martin!
Funny thing is, I asked around and finally was directed to the head honcho. He had nothing, absolutely no information on the foam. He said if I need something branded and rated, he sells DOW XPS. I want to stay away from XPS because of its high environmental impact, not to mentioned expense. I will try calling their other yard and see where that gets me.
Perhaps the better question is, when you lay EPS for foundations/slabs, does it usually have some kind of brand/R-value marking or is totally blank white foam normal?
I've seen a fair share of sheet EPS, and aside from faced sheets I've never seen any markings on them.