All-borate cellulose in attic
stk
| Posted in Energy Efficiency and Durability on
My contractor is proposing to blow in (dry) a Greenfiber product that is primarily meant for damp-spray application (INS735). I see that Greenfiber also has a product intended for blow in application (INS765LD). It would appear the main difference is the level of dust, as the dry-blown product is lower dust.
Both products are all-borate.
Should I hold out for the dry blow product? Not sure why contractor did not voluntarily recommend it for my attic.
Thanks.
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Replies
When I brought up using the INS765LD product, the contractor proposed using INS735, saying it was basically the same thing. I'm taking that to mean they aren't interested in using INS765LD. I'm in the NW (Seattle area), so maybe not all the Greenfiber products are available here?
According to the material data sheets, the only difference is that INS765 has plant starch added. Coverage charts show that about 13% more material is required to reach the same R-value as INS735. Unless there are locations where you are trying to maximize R-value in a contained space, and they aren't charging you extra, there doesn't appear to be a problem with what the insulator proposes.
Thanks. I'm puzzled by why one would be that much less insulative than the other. All I can imagine is that the damp-spray product has so many fines (particles) that it has less cavities to hold air? I'm also not too keen on the added weight to get the same R-value. R-49 minimum, thinking of going to R-60, should not be an issue with sagging due the added weight? Joists 2 X 6, 16" o.c. with 1/2 inch drywall.
FWIW, I emailed Greenfiber, and they mentiond for me to see if the contractor was going to damp spray INS735 into the attic. I had never heard of damp spraying into an attic (only walls), but I don't claim to be the expert Greenfiber is. When I asked the contractor, they said they would be blowing it in dry.
Actually, looking more closely at the coverage chart (attached), for loose-blown in attics the two products are virtually identical when it comes to R-value per installed depth. I had been looking at the column for weight per bag. No surprise, the starch-treated version weighs a bit more.
Cellulose installed in relatively deep amounts over 16" o.c. ceiling joists is pretty self-supporting.