Air sealing abilities of spray-in Spider fiberglass?
More and more, it seems like clients in my area are hesitant about open and closed cell polyurethane foams. I’ve never had an issue with them, though having a minor background in polyurethane chemistry through a family connection, I dislike the narrow tolerances for field conditions and component mixing. I’d like to try spray-in Spider (the sticky stuff) for a current project but have been unable to find good information about its air sealing capabilities compared to open cell foam – just a minor comparison of the loose fill variety spider to blown cellulose, which showed them as about equal. I’ve also found a couple message board anecdotes from folks who believe the performance is worse than JM indicates. JM seems to leave air infiltration test results off most product literature – but they include it on the literature for their open cell foams.
Anybody have good (hopefully 3rd party) data about air infiltration through spray in spider? I would assume it’s worse, but just wondering if we’ll need to spec any precautions beyond what we’d do for open cell foam in a mixed humid (zone 3/4 border) climate.
Much thanks.
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Replies
Chris B,
For a little more information on this issue, you may want to read the comments on this page: Getting to Know Spider Insulation.
In Comment #5, Dana Dorsett wrote, "Can they really hit 1.8 lbs density without netting? I'd previously been led to believe that open-sprayed Spider ran about 1.0-1.2 lbs density, and that it took netting or wallboard to hit 1.8 lbs, due the highly springy nature of the fiber. This would be an important distinction in assemblies that are not meticulously air-sealed, since air retardancy of 1 lb Spider is fairly lousy compared to damp-sprayed cellulose, or even open-blow attic density cellulose, whereas @ 1.8 lb density Spider's air retardancy is up there with dense-packed cellulose, and @ 2.2 lbs+ is measurably more air retardant than dense-packed cellulose."
I'd be interested in reading input from GBA readers with any experience to share.
Here's my conclusion: for new construction, I can't imagine that any architect or builder who cares about airtightness would depend on Spider insulation to provide an air barrier. Every wall and ceiling needs an air barrier, and it's not going to be Spider. It's going to be something else: taped exterior sheathing, specially detailed drywall, or a European membrane.