Ammonium sulfate offgassing from cellulose
I’m trying to decide how to best insulate a 1950s cape cod style attic being remodeled. A local cellulose contractor proposes to put up scrim and apply stabilized (wet-spray) cellulose, but will not apply an all-borate product because, he says, it requires too much moisture to activate the binder. He insists on using a product with ammonium sulfate instead, and says that once the initial install has dried it cannot offgas further, even if it gets wet.
I am trying to avoid dry cellulose due to the concerns about the load it would put on joists that are already flexing enough to cause hairline cracks in the ceilings below, though the cracking may also be due to the cement board used in the ceiling — a product not nearly as flexible as modern drywall.
There are a few online articles warning against using cellulose with ammonium sulfate due to corrosion and offgassing, but there seems to be a dearth of hard science online about the consequences of using ammonium sulfate in cellulose insulation.
Can anyone point me to research on this and other topics related to wet-sprayed cellulose? Rather than trying to research the risk, would I be better off avoiding it altogether by looking for another contractor — one who is willing to install an all-borate stabilized cellulose? The first guy took a while to find, so I’m not enthusiastic about restarting the search, being way behind schedule already, but I’m even less enthusiastic about making the wrong choice at this point in the process.
Thanks for considering my plight!
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