How do I vent a low slope cathedral roof system


#1

Sorry for the previous post, hope this makes more sense!

I live in upstate NY and have been asked to remedy a low pitched cathedral roof section that has noticable signs of water damage at the ridge where it meets a steeply pitched section, on the other side. The wall board tape is peeling, etc. The owner says that when there is a warm up, the water starts dripping. I suppose that moisture is entering the roof cavity through the can lights and freezing. The cathedral is less than 2:12 and meets a 14:12. The cathedral is insulated with 12" bats and has a vapor barrier between insulation and sheetrock, but no air space for venting. The ridge is not vented on the cathedral side, but has soffit venting. There are also can lights that are probably leaking heat and moisture, not helping the matter. If I gut the ceiling and insulation, pull the can lights, provide air space with styrofaom baffles to the ridge, add vapor barrier, **how do I than ventilate this tricky low slope situation.**There is currently a ridge vent situation that goes from the steep slope over the top to the low slope, but there is no way for the air to get into it from the low slope, no air space cut into the ridge on the low pitch. I think the the ridge vent might also leak where it comes over onto the 2:12.


#2

I would remove the canlights and use spray foam insulation, if youre going to go through all that. You shouldnt need to vent this configuration. What type of roof is on it?


#3

Roof has a torch down membrane on it in good shape. Can the spray foam be sprayed on the bottom of the roof decking? without an air space on underside of roof deck?


#4

Yes, but the airseal it creates often times requires the addition of a dehumidifier. This may not be the case since you already have a vapor retarder and insulation in place.

If you have it done, be sure to insulate every space that contacts the outside (fascias or eave closures). You also have to follow local building codes for fire safety barriers.


#5

Also, be sure to use a 2# closed cell foam.