Tips for obtaining recycled scrap insulating board?
woozy
| Posted in Energy Efficiency and Durability on
I was able to obtain a truckoad from a roofing company several years ago, but now I’m having trouble sourcing it.
Any hints from the experts? I’m in North Texas.
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Search the local craigslist for rigid + insulation eg:
https://dallas.craigslist.org/search/sss?query=rigid+insulation
Thanks!
Also on craigslist, look for it by name "EPS","XPS"or POLYISO".
Old foam is a hazardous waste (ie, it costs them money to dispose of it properly) so every once in a while there is a great deal BUT the catch is usually that you have to arrange transportation. I scored 125 sheets of R14 EPS from a refrigerated building reroofing, including delivery, for $10 per sheet, but that was freaky good luck,
Good luck. For under-slab, recycled roofing EPS foam is the way to go.
Ken
One of those suppliers is very close, and I have both a trailer and an 8 ft, deep bed Tundra, so I'd just make some trips. But yikes, a lot of the Craigslist stuff is expensive.
I'm thinking about doing the whole envelope, not just under-slab. Does an older production date, or damage to the recycled product, make this this a bad idea?
Older polyiso blown with CFHCs is actually higher performance than newer stuff. But since you don't really have a good way of knowing, assume any recliaimed fiber faced roofing polyiso is about R5.7/inch.
DON'T USE POLYISO UNDER SLABS OR IN CONTACT WITH SOIL!
Polyiso is hygroscopic, and can become saturated, losing performance when used in direct contact with the soil. It's fine for the INTERIOR side of crawlspace foundations & basements, but not the exterior.
EPS & XPS are fine for soil contact. The performance of EPS doesn't change much over time. Most reclaimed roofing polyiso is 1.25lbs per cubic foot density "Type VIII" goods which runs about R4.0 per inch. Some is Type II (1.5lbs nominal density), which runs R4.15- R4.2/inch. The compressive strength of either is fine for under slabs, slab edges, etc, but not for under grade beams or footings (unless an engineer has done the math.)
XPS starts out at R5/inch, but over time drops to R4.2/inch when the HFC blowing agensts are fully depleted. From a design point of view assume no more than R4.2/inch for any reclaimed XPS.
In North Texas (the warm half of climate zone 3A) subsoil temperatures are in the ~70F "Goldilocks Zone", and there is little benefit to insulating under the slab. R4 is fine, R8 is overkill, except perhaps for the first couple of feet of slab along the perimeter. But insulating the slab edge with R8 or more down to at least a couple feet below grade is usually worth it from a wintertime comfort point of view even though the IRC doesn't require any sub-slab or slab-edge insulation. So, 1-1.5" of reclaimed EPS or XPS under the slab, 2-3" of EPS on the slab would pretty much do it in that region.
Foam reclaimers have caught onto the fact that scarred up dinged and broken foam board isn't worth much. Most lots of reclaimed foam is in pretty good shape, with most sheets nearly-perfect, and perhaps 10% with superficial damage, and fewer than 1 in 20 that are too messed up to use. If you buy 15% overage to account for damage and scrap you'll usually have plenty of good material left over.
I was planning to only insulate the perimeter of the slab, and if it isn't horridly expensive, use stay-in-place insulated forms. Perhaps I should consider R-4 under slab?
Then, very good exterior sheet insulation on walls, with superior sheet insulation thickness on roof. Hoping for ~R-60 or better overhead. Oversee air sealing like a shrew.
My heart's desire has always been ICF (maybe even wood-chip cement forms). I even went to ROC a few years a ago. But it just doesn't cool off much at night here, so I'm undecided, since there doesn't seem to be a big advantage from the thermal mass in this climate.
I also considered metal framing combined with foam sheets, but with highs of 115* and lows to 0*, I decided against that.
My goal is the best, "box", possible for my climate, within a budget. I appreciate this help very much.
Even the thinnest ICFs are overkill here, at ~R16. Installing a couple inches of reclaimed roofing EPS (~R8) edge insulation down to the footing on the exterior of the stem wall after waterproofing the stem wall is cheaper, and just as effective as a minimalist ICF. It's also allows easier quality-inspection & waterproofing of the stem wall.
With a reasonable design and good air sealing it's possible to hit Net Zero Energy in North Texas with (termite-proof) steel stud framing insulated with cheap low-density fiberglass between the studs and 3" of exterior polyiso in the walls, as long as you have the right windows and R50+ of cellulose in the attic.
I would be so happy to call the steel building guys and do steel framing. I had a misconception about how much exterior foam it would take to nullify the metal.
I also have some ideas that would benefit by a span that would accomodate very few few-to-none interior support walls. I want to do moveable walls, among other unusual features that would benefit from a nice span, like having free air movement for just a few mini-splits.
I'm pretty excited to do metal framing. Thank you!
The thing to stay on top of with metal framing is to be sure the window bucks and door framing aren't highly conductive steel penetrating the exterior foam layer. Any steel that penetrates through the foam is robbing it of quite a bit of performance- details matter! A continuous layer of foam connecting wall foam to roof foam would avoid some of the potential thermal bridging issues at the wall to roof transition, but it makes for a fairly expensive roof insulation. Even with 5.5-6" of fiber insulation applied under the roof deck you'd still need ~6" of roofing polyiso to hit the R45-ish whole-assembly R for a cathedralized ceiling ("compact roof") recommended in Table 2, p10 of this document:
https://buildingscience.com/sites/default/files/migrate/pdf/BA-1005_High%20R-Value_Walls_Case_Study.pdf
A 2x6/R20 steel studwall with batts designed for steel framing (they're wider than those designed for milled lumber) will come in at around R9 for that layer after thermal bridging. A 2x4/R13 steel studwall comes in at about R7.
A continuous 3" layer of reclaimed roofing polyiso over the exterior adds another R16+ to the stackup, bringing the total performance to something like R23-R25 whole wall.
By contrast, a milled lumber 2x6/R20 16" on center studwall comes in at about R15 whole-wall.
Most steel framing in commercial construction is sheathed with fiberglass faced gypsum board (GP DensGlass or similar), and that would be appropriate here.
I don't really mind spending most of my budget on the envelope. I've collected at lot of stuff for the interior, including a European-style kitchen that isn't taxable; (not permanently attached :) Texas property taxes are so vile.
I've scrounged a lot of stuff from remodeling fancypants houses. For me, it's all about the energy savings. I hate it when women care only about the granite. {{{Look at the windows, you dope!! }}}
This information is priceless to me; to get it straight from an A++ expert.
Project documentation?
@ Lynda, sounds like an interesting project, different than many that are featured here; southern, steel framed, exterior insulation, moveable walls, and scrounged components (at least some of them). If you have a chance to document or at least photograph the project as it progresses, this is something that I think many readers here would like to see.
Good luck, and have fun.
I have very nice camera equipment. I hadn't really thought about actually documenting this from the beginnng, I guess I thought a box would be boring, but I like this idea. I'm sure my many mistakes alone would be useful to document.
I'm going to try to do central core utilities and the most economical runs possible, plus a lot of things, "out of the box", for both economy and for avoiding the illogical features that we accept so readily. Really, why do we flush our toilet right by our toothbrush and towel? Eww.
I think my biggest challenge will be oversight of the workers to make sure that the insulation and air sealing is done well.
Dana,
What's the consensus on using polyiso/polyu on the exterior of a building's walls (ie. on top of the sheathing)? For discussion, presume it's taped, under building wrap (ie. Tyvek), has a rainscreen and some sort of cladding (ie. vinyl).
I ask due to this statement:
"Polyiso is hygroscopic"
Thanks.