EPS insulation
Hi everyone. I have been following GBA for years . It’s been a great source for building info and advice and I have learned much, and sometimes just made me more confused[LOL]. I am getting ready to build a home for myself. It will be a timber frame hybrid and I am going to use sheets of EPS for a lot of the exterior insulation. I have done quite a bit of research and have decided this product would be the best for my situation. Here’s my questions I can’t seam to find answers for.
1. does EPS with recycled contend used along with virgin material change the R-value?
2. I want to use Neopor in the foam, does it make sense to just use it for the first or last layer and the rest regular EPS ?
Thanks, Ron
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For #1, there shouldn’t be any difference although I’ve never seen EPS specifically mention if it’s made from recycled or virgin material before. About the only difference between recycled plastics and virgin plastics is the length of the polymer chains in recycled plastics tend to be shorter, but that only affects the physical properties of the material in a few circumstances. I’m not aware of any issues with EPS specifically, or polystyrene generally which is the polymer EPS is made from.
I don’t have any info for you on #2.
Bill
Ron, EPS and Neopor (generic name GPS) are unique among foam insulation in that they maintain a constant R-value over time, so if you are using recycled sheets in good condition they should insulate as well as new material. If you are talking about new insulation that includes recycled content, it should be consistent with the product type--in other words, the same as other EPS or GPS of the same density. The manufacturer should provide the tested R-values of their products.
I can't think of a reason why it would matter where in the assembly you use EPS vs. GPS--unlike polyiso, EPS and GPS performance does not degrade as the temperature drops. I would look at the cost per R-value and consider the overall thickness.
> does EPS with recycled contend used along with virgin material change the R-value?
At any given density the R-value of EPS is stable over time, but R-value varies by density. A lot of reclaimed EPS is 1.25 lbs per cubic foot density "Type-VIII" goods, which is typically rated about R4/inch @ 75F mean temp, R4.3/inch @ 40F mean temp, R4.5/inch @ 25F mean temp. This is about 5% lower than typical numbers for 1.5 lbs density Type-II EPS.
If you look carefully through the specs for Neopor you'll also see performance differences dependent upon density.
I have been talking with several different manufactures of EPS and what they all tell me is that the increase you get in R-value doesn't warrant the cost increase for higher density foam. For example type 1 foam has a minimum density of .90 lb/ft3 and a R-vaslue of 3.85 at 75 degrees and 4.17 at 40 degrees. If you double the density you also pretty much double the price and only gain .65 in R- value. I am using it for roof and wall insulation so I am told type 1 should be fine, I was worried about compression from the sleepers that will be installed over the foam on the roof, mainly at the edges but if I am carefull at install this shouln't be a problem.
I stumbled upon GPS foam by accident while hunting for suppliers. What I am told about adding the graphite to the foam is that it increases the R-value to 5, but also has a reflective ability that increases its performance by essentially reflecting heat either out or back in towards the structure depending on the season.[marketing hype?] It would be made with type VIII foam[1.15] minimum density.
So my question about the GPS foam is does it really work, and if so do I need all the layers to be GPS or just 1 layer strategically placed in the layering?
The low density stuff is much more of a pain to work with since it’s crumbly and breaks easily. The higher density stuff is closer to XPS in terms of the physical structure. That’s something else to think about. If you go with type I EPS, you’ll want to cut it with a hot wire type cutter, anything else will make a mess of things.
Bill
I'll second what Bill said. Type 1 EPS (10 psi) is so crumbly that it's hard to work with. Type 2 (15 psi) is more like working with typical XPS, just a bit more crumbly at the edges. It has enough compression resistance for most situations. Other types with higher densities can work under larger structural loads.
GPS is available up to R-5/in, depending on density--about R-1/in higher than EPS. I have not heard the claim about reflecting heat and I do not believe it is accurate unless it has a reflective coating such as aluminum foil.
If you aren't concerned about the assembly thickness, I would not spend extra for GPS. But if the added R per inch is worth it to you, it does not matter where in the assembly it is located.
While I haven't used it on a project yet, I've been looking at GPS vs EPS, and our local (PNW) Insulfoam rep quoted GPS as being slightly cheaper than EPS on a per-R-value basis (R-10 GPS was cheaper than R-10 EPS). Insulfoam sells both EPS and GPS, so it seems like a fair comparison as far as I can tell.
Hi Michael, I'm a little stuck on Type VIII GPS vs. Type II EPS as well, considering ease-of-use and compression during installation...
...Is GPS a similar crumbli-ness as Type 1 EPS
Also I asked about the the recycled content because 1 supplier says it s about 1/2 the price as all virgin foam. I don't know if the recycled ground up foam they mix with the virgin material during processing is the same density or not. I will have to look more into that.
I have samples of type 1, .90 lb type IX 1.8lb and type XV 3.0LB. I agree the denser stuff would be easier to work with. I originally had the type IX quoted, but it was almost double the cost of type 1. I haven't checked on type VIII yet. Where do you draw the line between ease of installation and cost? The R-value is to close to even consider in my opinion.
The less dense stuff is a tiny bit more vapor open compared to denser materials, but not enough to make a huge difference in most cases. With a hot wire cutter, they all cut pretty easily. With a saw, type I is a nightmare to cut — the little beads and shredded saw fluff goes everywhere and sticks to everything. Type I is also more brittle and more likely to break if bent or fit too tightly into an opening. Type I is especially susceptible to broken off corners.
I would try to avoid EPS in full sheets that need cutouts to fit around things. Full sheets used uncut, the way you’d use them for exterior rigid foam in most places, is not as much of an issue until you get to openings for windows, doors, and anything else.
EPS works just fine in smaller spots like between joists along a rim joist. I used it myself for that spot because I wanted a bit more vapor open insulation there since I have foil faced polyiso on the exterior. I cut the pieces with a homemade hot wire cutter, then loose fit them and sealed them in place with canned foam.
Carrying full sheets of thin EPS is asking for breakage. You have to be careful and carry the sheets sideways the same way you have to handle hardi plank siding boards. If you’re careful, use a hot wire cutter, and know the spots where the material is most likely to be difficult to use, low density EPS works just fine.
If you have a lot of details to cut, the denser types of EPS are easier to handle. You could potentially use high density EPS in places where you have a lot of cutting to do, and maybe on exterior corners where the material is more likely to be damaged, and then use low density EPS everywhere else to save money.
If you have any doubts, buy a sheet of the low density stuff and play with it a little. If you get frustrated and yell at it a lot, get the higher density stuff that is easier to work with :-)
Bill
Michael, thanks for the input.
neopor is a brand name by BASF, the creator of the process. would you mind going to this sight and read the brochure and let me know what you think http://www.neopor.basf.us
Thanks
Ah, I see--I had not looked into how GPS achieves its higher R-value per inch than EPS. It makes sense that the silvery graphite reflects energy within the material, on a micro-scale. But I don't believe it also has a radiant effect on a macro-scale, the way foil facers gain about R-1 when they are within an assembly (and with an air space on one side of the reflector).
I also noticed another foam company gaff--they can't seem to help it:
"Most polymer-based foams exhibit a greater ability to slow the movement of heat as the temperature decreases. Neopor GPS is in a unique class because it increases in R-value as the temperature outside drops."
Correct me if I'm wrong, but aren't those two phrases describing the same effect?
thanks for the reply Michael. Got to love the double speak !
So do you think the GPS is worth the added cost over regular EPS?
On another note I just read a post about exterior foam on a timberframe and it seems that anything over R- 38 of foam on the roof is wasted money?
I am in climate none 4 in that little bump that reaches into south eastern Pa.
>"On another note I just read a post about exterior foam on a timberframe and it seems that anything over R- 38 of foam on the roof is wasted money?"
It depends on what your total goals are, and the design of the rest of the assembly. If the goal is meeting code minimums, R38 c.i. on the roof is usually going to make code minimum, and there are usually other places where the bang/buck is better than an additional few inches of EPS. Virgin stock EPS foam is pretty expensive, R for R.
But using reclaimed roofing foam makes it a lot more cost-rational to go better than code at the roof. Reclaimed roofing polyiso or reclaimed Type VIII roofing EPS is often cheaper than mid-density fiberglass batts, R for R, though not as cheap an installed price as 1.5lb open blown cellulose on the attic floor.
Dana, I have been exploring a ton of different EPS options. The most economical I have found is virgin EPS with about 25% recycled content mixed in. I had concerns that this would affect R value or density and was told it shouldn't. It is almost half the cost of all virgin foam. I also looked at GPS FOAM, I can get this for .28 cents a board foot 1.25# density. I would consider rock wool but the cost monetarily is more than I want to pay. This is our retirement home and I would like it to be a[pretty good home] so I am trying to find the right balance. I am open for opinions.
Do you have any aversion to using reclaimed materials? Reclaimed insulation such as the reclaimed roofing foam Dana mentions is a great option in places where it’s hidden so no one will see any scuffs or crunched corners. The insulating value is essentially the same as new material, but it’s cheaper and didn’t get wasted filling up someone’s dumpster. It’s easy to deal with any crunched edges by injecting some canned foam between sheets when you put the material up.
Bill
To be honest I haven't looked into reclaimed material, I should. I just think it will be hard to find the quantities and specific sizes I am looking for , but it can't hurt to look!
I did a quick search online for reclaimed material and almost all of it is the same or higher price than what I can get new for. The quantitiy of enough in the same size seems to be a problem also. I will check with some comercial roofers on Monday