The only attic ventilation now is passive through the soffits and ridge vents. Active ventilation was on my list but now I've struck it off based on your post. 3/4 of my attic space is vaulted -- I can't get flats up there, maybe it can be blown, but if it's blown how do they go about inspecting it for proper application? Or is it more like BGA assembly without X-ray inspection (spray and pray?)
For blown insulation (I think you mean fibers, not expanding foam), I think the installation method integrates a basic check, i.e. you cut small access holes on both ends of a space you are filling, and it is pretty obvious whether bulk material makes it to the other end to spill out. You probably need a stud-finder or similar to map the spaces between rafters, fire blocking, etc.
The best way to plan or inspect an insulation job is to use an infrared camera to observe temperature gradients. You can see hot or cold spots where heat is conducting or convecting through the structure.
Maybe I'll luck out and the vaults won't need remediation. Yes I was thinking fibers, not foam. I'm sure I'm underestimating the effort eeded to do a proper job on the vaults within the things' narrow confines: Access to two of four vault edges doesn't seem possible without punching through the gables from outside.
Thank you for the practical suggestions on moving forward. Email me in profile if you're in Largo or Sarasota FL sometime and I'll buy you a brewski or coffee or something.
For retrofit, I think it is more common to cut 1-2 inch openings through the ceiling or wall face (i.e. cut through plaster or remove pieces of paneling), blow the insulation, and finally patch those holes. And, this pattern will repeat every 5-10 feet, since the bays should be physically divided along their length by fire-blocking if built to code. Each blocked section will have to be filled as a separate step.
Disclaimer: I'm not an HVAC professional, but I did apply closed cell foam insulation to one of the rooms in my house.
In my experience, the spray does a very good job of sealing the joints where applicable. That's probably not the right type for an attic, but more insulation would generally be better than less.
That's not a particularly scientific approach, but when we're talking about old houses, you're almost never going to be able to do everything the way you want 100%.
I'm trying to envision what you did. Were you sealing up penetrations in an exterior surface or along a joint edge or were you filling voids in for ex the wall? I had good results filling a nasty opening around a water pipe with the spray but it didn't last because I failed to observe the warning about UV degradation and the material eventually flaked away.
