My ceiling is sips panels, and due to bad advice they were installed as straight edged 4x8 sheets with 1/2 gaps, the idea being to blow foam in the seams. Although I'd never recommend it, it did work for the first couple of years, but the earthquake this summer ( I am 45 minutes from the epicenter in Quebec) must have broken my foam seal and now I have some condensation issues. The ideas I am throwing around are:

-2x3's on edge and blowing an inch and a half  of urethane, but this is an expensive solution. I am also considering (wondering if people here think it will work) stripping it down to the plywood and laying 2 inches of rigid, taped and  held down with the strapping. In my mind this could allow for more of a floating sort of vapor barrier, not succeptible to any leakage caused by shifting.

the question:

I think the ratio for a vapor barrier is not to have it further than 1/3 of the way through your insulating wall from the inside, so will the two inches of rigid after 91/2 inches of foam be too far past the freezing point to make a difference?

other than that any suggestions are welcomed, wondering if anyone else has seen condensation leaks in ceiling sips and how they might have dealt with it.

thanks.

Dear Mc Bain, there is something to learn from your problem, i would like to know more of it, and perhaps we could find a solution to your problem.

Call us please, we are in Acton Vale, Quebec, and we make SIP'S, ans we do not want to make that mistake.

Pierre Desjardins
Banerpan

Do your panels have lumber splines in them or are the joints just the panels with the foam core flush to the OSB skin edges and then spaced 1/2" apart?

thanks Pierre, I'd love to get in touch. I have worked with several different sips joint designs trying to avoid the very problem I have, I did mine about 6 years ago.

Simon-

No lumber splines, It is a timberframe roof with a 6/12 pitch. The way we did it back then (never again, not my idea) was drywall on one side, 9 1/2 inches of foam, and osb. Straight edge panels all around, the crane would drop them on the roof, we'd nail them down with half in spacers in the joints. so you could see straight through to the inside of the house. Since then, the four homes our small company did like that all had condensation issues. Mine we did in summer compared to colder temperatures with the others, so I think that helped because the foam expanded properly. I did the whole thing, let it expand then did it again, 3 times.

As I say, it worked fine until that earthquake this summer, now I have 3 problem spots. I caulked some spots inside along the beams so that the air wouldn't travel through, it helped a bit but I want a permanent solution.

thanks.

I think the problem is the cold air seeping in through the gap created by the gap filling spray foam shearing away from the panel during the quake. How about resealing the split with an elastic chaulking (solvent free) then use a flexible elastic membrane type adhesive tape on all the joints to make them air tight again. The problem is you have rigid foam joints, but they are not rigid enough (urethane spray foam is brittle) to resist the movement, so design flexible insulated joints that allow movement. Flexible poly styrene foam backer rods could be used too.

I'm pretty sure covering up your OSB in a cold climate with foam sheeting can cause moisture damage to the OSB

interesting idea Simon, thanks. it is definitely air seeping up that is my problem, but whatever the solution unfortunately I have to remove the tin, since it is a timber frame with purlins and rafters, the majority of the joints fall on top of the beams. I was just talking with Pierre, and I think with your ideas and his, I think I might have come to a solution. I think at this point I will chainsaw out the gaps, find a flexible accoustic seal type product to fill in as the vapour barrier, put more insulation and tape it up with Resisto.

So thanks, and thanks Pierre as well.