Poor Comforboard availability. Alternatives?
We’re building on the Southwest corner of climate zone 5A (Northwest Kansas). Hoping to be able to heat and cool with electricity from solar so we’re trying to build for efficiency.
ICF walkout basement
2×6 walls
external insulation
ZIP sheathing for the air barrier (shooting for less than 1 ACH50)
We were going to do Rockwool for both the exterior insulation (3” of Comfortboard) and inside the external wall cavities but the walls are going up very soon and we didn’t expect comfortboard availability to be so poor. Now we’re looking for alternatives. Haven’t really researched alternatives much so I don’t even know where to start. My builder has never used external insulation before so he doesn’t know what to think either.
Any suggestions?
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Replies
Call rockwool and tell them, many times they have a wholesaler in your area that you would not think to call that can supply you. Owen Corning also makes a mineral wool board insulation, again call them and see who in area supplies Owen Corning insul and they can probably get it. Otherwise foam is the other option. But I would start with calling Roxul
@freyr_design, Dane Edelman has posted on this site from time to time and he used to work with Rockwool.
He would post his email address on here pretty regularly so I contacted him in August in regards to finding Rockwool. He pointed me towards a distributor and the distributor said 8 weeks was the availability back then.
Now that we’re getting closer to using it we called the distributor again to order and they’re now saying September or so.
So I emailed Dan again to ask him if he had any other sources and the email bounced making me wonder if he no longer works for Rockwool.
ya I'm not sure about him but you can just call their corporate office and they will put you in touch with you regional rep who will have the most up to date info. When I did this on my last project the supplier had what I needed in stock, as well as a few commercial customers who had over bought that were attempting to offload their extra stock.
One note, you may have different luck with different sizes and thicknesses. Generally they are all the same price per sq ft, will just take different install time and perhaps more temporary fasteners. You can always layer if other thicknesses are available. I know 2x4' sheets are available in my neck of the woods (inquired last week) currently, but I am far from you and have no idea what is over there.
Called corporate today. They directed me to a different distributor as well as one of their sales reps.
Basically sounds like availability is currently as bad as it has ever been. I think I’ll just go another direction.
There are two places you can get it readily available, one shipped for free.
Google Roxul instead of Rockwool and SKU 40220.
So you're googling "Roxul 40220"
1", 1.5", and 2" is more available. Per Comfortboard 80 install specs, stacking and overlapping are both fine.
Polyiso and EPS are both lower GWP than Rockwool. And polyiso has a much better R-value than Rockwool. And cheaper. So why wouldn’t you choose one of those?
@matthew25, like I said, I haven’t really looked into anything other than Rockwool for whatever reason.
Your reply prompted me to look into polyiso and EPS. It kinda looks like maybe the GWP commonly associated with those products maybe does not include the mfg process of said product and that maybe Rockwool is better in that regard?
Also, it looks like polyiso gets worse on its r-value as temps go down. When temps are low is when insulation is most valuable so I am a bit skeptical of that being a good course to pursue without more research. Maybe it’s so cheap that you can afford to do a lot more of it than Rockwool?
Looks like EPS R-value actually increases as temperature decreases so maybe that would be a good path?
Not sure what source you are looking at for lifecycle analysis, but manufacturing is definitely included (A1-A3). See Page 5, Figure 1 in the below link for an LCA overview. The GWP values for polyiso and EPS are on Page 9, Table 1.
https://www.efficiencyvermont.com/Media/Default/docs/white-papers/The_High_GHG_Price_Tag_on_Residential_Building_Materials.pdf
Looking up the Environmental Product Declaration info for Rockwool Comfortboard 80 (link below) I see 4 kg CO2e. Comfortboard 110 is 5.6 kg CO2e. Polyiso is 2.3, and EPS is 3.5. This is only including A1-A3. Because that’s all Rockwool made easily available. So possibly double the GWP depending on which product you choose.
https://www.rockwool.com/siteassets/o2-rockwool/documentation/technical-bulletins/commercial/epd-gwp-look-up-tables.pdf
Also, as others have mentioned numerous times on this forum, the cold weather performance is misunderstood. It is referring to the average temperature across the foam, not the outdoor temperature. And even with the derating in cold weather, the R-value of polyiso will always be higher than both EPS and Rockwool. So again, why would you choose Rockwool.
I’m not upset at you specifically, but the fact that the general public thinks melting slag at over 1500 degC to create Rockwool somehow makes it environmentally friendly is certainly the greatest marketing con of our generation. They have fooled everyone I think.
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I forgot to mention, one thing I really liked about Rockwool was its fire resistance and of course the fact that it is way more vapor permeable than foam.
Around me Lowes carries it[or did] so maybe they can get it? Not like you are looking for one package
Lowes is out of stock as well (at least near me). Everyone I've called has months-long wait times. The big downside to non-rockwool products is the lower permeability. Comfortboard has a perm value of 30 while EPS is only 5. Still, plenty of homes are designed well with EPS or polyiso. @dpilot83, take a look at https://basc.pnnl.gov/building-assemblies/5a for some ideas.
I looked up my local Lowes and sure enough, no comfortboard, but two other brands of mineral wool. Is there a reason that the brand is important?
You can (and should) use mineral wool batts from any company for the stud wall cavities. It's the exterior insulation where you would want/need Rockwool Comfortboard 80. It has a higher compressive strength for installing fasteners/strapping. If you used batts on the exterior, it would be very, very difficult to avoid over-driving your screws, leading to siding installation issues.
I believe Johns Manville makes their own rainscreen mineral wool called Cladstone or Curtainwall, but I'm not very familiar with its availability or use.