Got a bid to foam the cathedral ceiling of my walk up attic. For $2800 bucks. A dollar a board foot. Three inches of foam.

The other bit of good news is that I would have to remove all the existing lath and plaster-then rerock it-which is a real PITA since its third floor. (Can’t even get full sheets up into the attic, not to mention grief from wife over dust)

The foam guy, who also does dens pak btw, strongly advised against drilling and denspaking my cathedral ceiling, on account of having only 5 1/2″ of depth in the cavity.

He said his cellulose reps say that anything under eight inches is asking for moisture issues. Which I dont really get-I though that if its denspaked, it wont allow moisture through to condense, right?

What would you do-bite the bullet and demo/rehang?

Cut out the sheating when I reroof and foam from above-if the insulator would do it that is?

Or just drill the existing ceiling and denspak it?

Airsealing is much more important to me than r-value, given the limited depth I have in the joist bay.

Also, lowering the ceiling to add more insulation isnt at all desirable as you can only stand up right below the ridge….