CoffeeGuy
Senior Member
I originally wanted to DIY closed cell spray foam, but the weather turned cold too quickly on us, so we pivoted and have been laying in layers of 1/2" polyiso board that we can press-bend into the ceiling contours. We are 3 layers deep now between the ribs. Next step will be adding 1"-ish furring strips front to back, and then adding more polyiso between them.
In addition to all of this, we're injecting foam insulation into the hat channel ribs (I found that it did add a couple degrees of warmth versus unfilled, using a contact thermocouple on a treated rib and an untreated rib) and we're going to add a thin layer of insulating tape to each rib before adding the furring strips. I should also note that there will be some small gaps between the roof and the first sheet of polyiso board. We used dabs of adhesive, but just enough to hold the board, not enough to seal with full contact.
Finally, we're going to attach thin plywood panels to the furring strips. There will be a thermal bridge from the ribs to the screw heads attaching the furring strips, but those will be covered by the plywood.
So what's the question? Condensation!!!!! Should I seal up all of the seams with aluminum tape before we get to that final layer of furring strips and polyiso? Should we add a vapor barrier? Should we add vents to the roof between each pair of ribs?
I honestly don't know what the safest course of action is. we will be heating with diesel heaters, not propane. We plan on chasing better weather, but there will be times when we're in colder stuff for short stretches. I don't want to do something that I have to tear apart and redo, so I'm looking for some guidance, especially from those who have been down this road and have had a positive experience using rigid panels rather than spray insulation.
Thank you in advance. I know this is the best community to ask something like this in.
In addition to all of this, we're injecting foam insulation into the hat channel ribs (I found that it did add a couple degrees of warmth versus unfilled, using a contact thermocouple on a treated rib and an untreated rib) and we're going to add a thin layer of insulating tape to each rib before adding the furring strips. I should also note that there will be some small gaps between the roof and the first sheet of polyiso board. We used dabs of adhesive, but just enough to hold the board, not enough to seal with full contact.
Finally, we're going to attach thin plywood panels to the furring strips. There will be a thermal bridge from the ribs to the screw heads attaching the furring strips, but those will be covered by the plywood.
So what's the question? Condensation!!!!! Should I seal up all of the seams with aluminum tape before we get to that final layer of furring strips and polyiso? Should we add a vapor barrier? Should we add vents to the roof between each pair of ribs?
I honestly don't know what the safest course of action is. we will be heating with diesel heaters, not propane. We plan on chasing better weather, but there will be times when we're in colder stuff for short stretches. I don't want to do something that I have to tear apart and redo, so I'm looking for some guidance, especially from those who have been down this road and have had a positive experience using rigid panels rather than spray insulation.
Thank you in advance. I know this is the best community to ask something like this in.
