I live in northeast PA on the side of a ski slope. My house is a modular which is 2 years old. Last winter we had a problem with moisture under the insulation due to the fact that the ridge vent was not working properly. This was because air was not going from the soffit to the ridge vent as there is a double joist that runs parallel to the ridge. The insulation was removed. However we have a cathedral ceiling in our great room and it was not possible to remove the insulation from that area. The ridge vent was replaced and we thought that the problem was fixed that only because this winter the temps were quite moderate. As soon as the cold temps came and variations in the temperatures we are having leaks coming down from the cathedral ceiling. Our contractor is investigating a remedy. One recommendation was to put in foam insulation. What is your recommendation? Thank you.

I'm confused. Why did you remove the insulation? Why did you replace the ridge vent? What kind did you have, and what kind was installed as a replacement? Do you have condensation, as you describe in your title, or a leak, which you refer to in your message? Where is the "leak" and how much does it "leak"? Why is there a double joist parallel to the ridge? Does the same double joist exist in the vaulted ceiling area? Where and how does the contractor propose to install foam insulation? What type of insulation does he propose, and how much of it?

As you can see, there are many more questions than answers. This is an issue that probably needs some thorough on-site examination to resolve. By all means, be sure you diagnose the problem correctly before a solution is selected. It needs more than guesswork.

Thanks for your quick response and additional questions. You mention an on-site examination. Is it possible that we could arrange that since you are in my area? To respond to some of your questions: Apparently and due to the modular construction it was necessary to fold the roof down (?) to bring the house to site. The house is 64' long and the cathedral is approximately 15' from one end, then a valley to the cathedral (20 foot high) and 26' long then another valley and the roof backs down again for the additional 23'. The house is oriented on site to run in length north/south with the portion of the house that has the cathedral ceiling facing north and parallel to the ski slope (approx. 40 feet from the house)where man made snow is made and at times blows back on the roof. Initially our contractor thought that the problem we were experiencing (water leaking down along a joist that comprised the cathedral and running down onto the walls of the room) was due to a combination of the man made snow sealing off the ridge vent and additionally possibly melting snow leaking through the valleys. The original ridge vent used has since been taken off the market (corrugated paper) due to possibility of some type of collapse. To go back to the installation of insulation in those areas of our attic space that were accessible. I found after noticing water dripping onto the attic flooring that a significant amount of moisture was collecting under the insulation. Insulation installed was Certainteed, R-22 with vapor barrier. The insulation contractor had drilled holes through the double joist and installed foam vents to allow air to flow from soffit to vent; however, upon inspection these did not always line up properly. The underneath sheathing of the roof was very wet. It took months after the removal to dry out the sheathing. At the time the new ridge vent was installed last April, the entire back half of the roof was removed and replaced with an underlayment over the whole area of ice and water shield. Sorry to mislead with leak v condensation but I make an assumption that the leak is condensation which is happening in the cathedral since their is no air flow from the soffit to the ridge vent due to the joist that runs across about 5-6 feet from the ridge. This is a sandwich made of the roof/sheathing and sheetrock with the insulation between and no way for the air to flow through. The open attic spaces now have very good air flow since we did not replace the insulation. I hope that I have responded to your questions in a manner that makes the situation clearer to you.

It sounds like you have some major design issues with the manufacturer of the modular home. You might ask them how they expected the roof to ventilate?

I'm still not clear about a lot of things, and I hope you are not saying that part of your roof in uninsulated, with this cold spell we're having?

Do you have a detailed set of working drawings for the house? Without those, it would be difficult to properly assess the problems, and even more difficult to suggest good solutions.

You can email me discuss on-site examination.

This message has been edited. Last edited by: Richard Hetzel,

For those who may have been following this thread, I had the rare privilege of being able to examine this particular house in person, and this what I think:

There are two quite large triangular areas of roof which are insulated but which have no soffit vents, and the path to the ridge vent is blocked by a double 2x10 running perpendicular to the 2x10 rafters, so that these areas are completely unventilated. They are each adjacent to a valley rafter, and it is along the valley rafters where water has appeared on the vaulted ceiling.

The first attempt to solve the problem will be the installation of dome-type roof vents, one in each rafter bay. About a dozen will be required. This is a relatively inexpensive process, and hopefully, it will ventilate the now-sealed rafter bays and allow moisture to migrate to the outside, and not condense and appear on the ceilings.

If that fails, then the ultimate choice will be to remove the gypsum board on these ceiling areas, remove the existing fiberglass insulation, and spray polyisocyanurate foam insulation, completely filling each rafter bay, and then replace the ceiling, some of which is 20 feet high. This will give an R-value of something like R-66, and this foam is closed-cell, which will not absorb and retain moisture. WE are hoping this "ultimate" solution will not be necessary.