Reclaimed rigid insulation – what to look for / ask for
Hello GBA Community:
I’ve engaged a builder to build a house in Guilford, CT (Zone 5). I’m looking into exterior rigid insulation and hope to purchase reclaimed insulation from one of the regional reclaimers. The house will have hardie board siding if that is relevant.
I have few questions:
1. What should I be looking for in terms of type of foam? We are on the warm edge of Zone 5. Is EPS preferable due to permeability? Can we get away with 1 inch of polysio even with cold-value performance issues? Must it be foil-faced or will any rigid insulation do?
2. Upon inspection, what should I look out for? Upon calling reclaimers, what questions should I ask? Is there any form use that is not desirable due to its effect on the insulation?
3. Is there any type that will be faster to apply than others? (I know my builder will be concerned about time.)
4. Is it acceptable to mix and match types / sources of insulation? What are the risks? I would only do so if I cannot find enough of the same type from a reclaimer.
5. Given that a minimum thickness to the exterior insulation is required to avoid moisture issues inside the walls if we end up using batt insulation, should I be over compensating on thickness due to degradation in R-value?
6. Given that the house will be on the warm end of Zone 5 (closer to 4A), can we cheat a little on the minimum thickness/R-value required for Zone 5?
Thanks in advance (and apologies if these questions have been collected elsewhere).
–Adam
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Replies
Adam,
Q. "Can we get away with 1 inch of polysio even with cold-value performance issues?"
A. One inch of polyiso will work in your climate zone for a 2x4 wall, but it's not enough for a 2x6 wall. More information here: Calculating the Minimum Thickness of Rigid Foam Sheathing.
Adam,
You may want to read these articles:
Choosing Rigid Foam
Thermal Drift of Polyiso and XPS
Cold-Weather Performance of Polyisocyanurate
All types of rigid foam will install in the same way -- some types aren't easier to install than others -- but foil-faced polyiso is the easiest type of rigid foam to tape.
What you are looking for is clean foam without damaged edges or corners. Ideally, the thickness of the foam will be consistent.
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Reclaimed goods thinner than 2" are fairly rare- most roofing foam starts at 2", and thinner stuff is more fragile and more likely to be damaged during demolition.
Any facer will do- most roofing polyiso is either fiberglass faced or more commonly asphalted paper/felt.
The higher permeance of EPS isn't going to make a lot of difference. Having more than the absolute minimum R value does.
If the lot of the stuff is in really rough shape with lots of broken off corners or obvious water or boring-insect damage (ants will sometimes tunnel in rigid foam, all type are susceptible) you might want to pass. Assume ~10% will have some damage, but even damaged goods are often usable when you are cutting out for windows & doors, etc.
Tapered foam is often used to give flat roofs a bit of slope, and that stuff is nearly impossible to use in a wall sheathing application. Foam that has spend a couple of decades in service often shrinks slightly, and not always evenly, but for 3" foam there is usually less than 1/4" of difference between the thinnest & thickest edges, but measure a few sheets near each corner just to be sure, to avoid having to shim out the furring for reasonable wall flatness.
It's fine to mix & match types, as long as the R-value is sufficient for dew point control.
If you're going to cheat the R a bit, be sure to run a WUFI simulation. In most cases you'll be better off with cellulose rather than batts when cheating.
Thanks Martin and Dana. Have you ever come across reclaimed Roxul Comfortboard, Thermafiber Rainbarrier or the like?
Rigid rock wool hasn't been widely distributed for long enough to show up as a reclaimed material just yet. It's also a bit more fragile and more likely to be damaged during de-construction.
There has to be a square mile of 2" roofing polyiso passing through the hands of southern New England reclaimers & factory seconds traders every year (a statistic I just made up! :-) ).
You'll notice that this factory-seconds trader shows tapered insulation (that you DON'T want), but I'm sure they have flat sheets too:
https://hartford.craigslist.org/mad/5900690664.html
Green Insulation Group in Worcester MA will always have something in stock, as will Nationwide Foam in Framingham MA, if the reclaimer in Bristol can't cover your needs.