We have a 1800 sq ft cape with a 26ft continuous ridge vent. For some reason there are no soffit vents. We just got a new roof last spring because we thought there was a leak and the old roof was 20ys old. Now with the new roof we are still getting what we believe is condensation on the under side of the plywood on the north side of the house. Frost is visible, then it melts when the sun beats down on it in the middle of the day. It almost seems the problem is worse with the new roof possibly because the new roof is tighter? We had the roofer come back and redo the ridge vent and make sure there were no gaps or leaks.

I now realize we need soffit venting in order to have enough air flow. I think right now warm air is being drawn into the attic from the house. We have vaulted ceilings with eaves on the sides. (no attic) The frost melts and we see water dripping from the plywood, and stains on the sheetrock on the bedroom wall where the eave begins.

I recently had a bathroom fan installed and I asked the electrician to cut a hole in the eaves and vent it out of the house. After going in the crawl space, she came back and told me that we had soffit venting, that was a different type hidden behind the gutter and that she didn't need to cut a hole. She then vented the fan down in the area where she claimed the soffits were. Has anyone heard of this type of soffit venting?

If we put soffits vents in, how do we know which type or how much? Should we get a continuous soffit which would mean replacing the wood the entire length of both sides of the house? Or can we use the 4 inch round ones every 3 ft or so and put screens in? If we go with the round ones how many and how far apart. We would like to do it right. Any help would be greatly appreciated.

 

Technically, continuous soffit and ridge vent is the way to go to remove attic condensation.
Cutting down humidity in your home may be easier if you don't mind a little dryness or static.

 

Bebop, the bathroom vent should be vented directly to the outside, usually with as short a vertical pipe as is practical. This way, the moist air in the pipe will be outside before it can condense. With the situation you described, there is an excellent opportunity for the condensation to happen inside the exhaust tube, and with the pipe pointing down, for the condensation to accumulate and cause all kinds of problems.

As for how much soffit vent, see my post on this subject for another poster today.

 

Thanks so much for your reply. We read your posts carefully and have some questions. Regarding this paragraph:

"Site, if the soffits are covered with insulation then the insulation has to be removed. No ifs, ands, or buts about it. While it is not scintillating type of work, it is something that most homeowners can do (especially if they want to be sure that it is done right). Once the soffit cavity is clear, you have to ensure that the air gets into the attic by using the styrofoam channels (noted both by Xsleeper and me), and use these to keep the insulation from obstructing the air flow. These styrofoam channels look a bit like giant egg cartons, with a "W" shape, about 24 inches wide and usually about four feet long. They are easiest to install with the soffit off and you pushing them up between the insulation and the roof sheating, between the rafters."

We went in the crawl space, and after pushing the insulation aside, saw light at the area where the soffitt should be. We don't have soffits; maybe just a smart vent. However, the insulation is completely blocking the air flow. We think our plan should be to install individual soffits every 3 feet, as well as the styrofoam channels. This sounds like the best way to insure that the air flow stays unobstructed. We love our house and every time the frost melts we watch our bedroom wall become wet and stained. It's heartbreaking!

In your quote above you say these channels are easiest to install with the soffit off - are you talking about 4 inch round soffits or a continuous soffit? Or do you mean the facia board as well?
If we're talking about the 4 inch round soffits with screens and the styrofoam channels, this is something we could probably do ourselves. If we're talking about a continuous soffit that means taking the gutters and the facia board down, then it's a little out of our league as DIYSers.

Also, we're not sure how much of the insulation to remove. If we use those channels, do we need to cut any insulation back? If the styrofoam channel goes in between the insulation and the plywood roof sheating, how can air flow up to the ridge vent? It seems like the insulation would stop the air flow. Might it go on the paper side of the insulation, in the attic area itself?

We would appreciate any advice you can lend. thanks, bebop and wife

 

If you don't have soffits but a "smart vent", then you need to figure out exactly how big it (they?) is and how many of them you have. That will help you determine if you have enough intake air.

The styrofoam channels are inserted between the deck and the insulation, usually compressing the insulation a bit. They are designed to give you 2-3 inches of clear air space, not the 4 inch channel that I like to see, but it's better than nothing. Yes, I'm talking about continuous soffit, which is removed to allow the channels to be inserted, then reinstalled. It is usually NOT necessary to do anything to the fascia board. Given that you do not have continuous soffits, the other way is to try and insert them from inside the attic, but that is a messy, itchy, and uncomfortable job. If you ARE going to do that, make sure you cover your skin to avoid contacting the insulation (fiberglas insulation can make you very itchy), and wear a breathing mask, since insulation fibers are not good for your lungs.

Besides the condensation issue, you also need to check whether you are getting leaks in your new roof. When your ventilation is poor, it is common to get ice-damming, which then blocks meltwater from running off the roof and allows it to back up between the shingles. If you did not have any underlayment (tar paper) installed under the shingles, then this backup will be going directly onto your sheating, and into the roof. Improving the ventilation will not always fix the problem. On the other hand, I did a low-slope roof for a neighbour (and friend), where we fixed a long-standing problem of horrendous ice-damming and frequent leaks, and there the solution was to greatly increase the ventilation as well as to install a proper leak-proof membrane. Now he has no ice-damming of any kind (not even a few icicles), and the roof surface is "tight as a drum".

Step back from the situation, and think carefully about what is cause, and what is "effect". The roof is a "system" that interacts with the house. Starting with the inside, you should have an effective vapour barrier, then insulation appropriate for your climate, then adequate ventilation, then a supportive sheathing surface, then roofing underlayment (which catches any water working its way past the shingles), then the roofing shingles and flashings. A defect in any of these will cause problems.