Venting Gambrel Attic with Cathedral Ceiling

dustbunniesDecember 17, 2006

I have a Gambrel house (barn roof)that has a small attic on one end of the house and cathedral ceiling on the other end. There are 3 small roof vents near the ridge spread along one side of the house. My husband installed a power vent on one gable end near the top. There are NO soffet vents of any type. It would be difficult to retrofit and install soffet vents because the roof was hand-built. Each angle of the roof was built separately. There is a 2" x 6" running the length of the roof at each "bend" in the roof. Thus even if I get air into the soffet, it can only travel up to this board that seals off the attic spaces. To make matters worse, the second angled part of the roof is actually the walls to my upstairs. Thus my walls are really "roof". These walls are built and insulated as if they are walls. They have about 6" of insulation in them with no venting.

We have a problem with mold in our attic, ice dams forming, and water leaking in around the skylight and in the seams between the OSB sheets. Water is tracking down the rafters, pooling on the first floor ceiling, and raining out of a light fixture in the bathroom. It is also "raining" in the second floor bathroom.

My attic did not have a vapor barrier and it had some sort of loose highly combustible insultation in it. We removed this fire hazard and installed 12" of fiberglass. We know we need to install more insulation.

The second floor bathroom walls were covered with tongue & groove pine nailed directly to the rafters. I removed all of this to check for the source of the water. At least now the water can drip straight down into buckets.

Most of the remaining roof walls have been drywalled. Oh, and for good measure I found that mice have been living in the eaves.

Any suggestions how to properly vent this mess without tearing out the roof? And how to insulate?

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sierraeast

Having a hard time picturing your situation, but could you concentrate your efforts inside? Removing wall board to access drilling venting holes, sliding styrofoam air channels up the rafter cavaties, adding insulation,etc.

You could take on sections at a time and not have to worry about the elements,although it will be a lot messier inside.
If you can access the 2x6 and get some venting holes drilled at the top of the 2x and run your soffit venting, this should help some, but agin,im not fully understanding your ordeal.

    Bookmark   December 21, 2006 at 11:06AM
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blackdogarch

Hi. Couple of things: Is this a very old house, i.e., had joined, minimal struture, no consideratin of insulation requirements...?
1. All appliances, bathrooms, sources of moisture MUST be mechanically vented, period, and vented outside, not to attics or eaves. This is critical!
2. The attic space must have a way in for the air or the fan will suck the moist house air through it, to condense on the roof and rafters;
3. Check for roof leaks, bad flashing, just in case this is a bad roof issue;
4. The side roof/walls (top of the gambrel) are too thin for good insulation, and are not moisture resistant or vented. If the insulation is fiberglass, it must be vented or extremely well sealed (almost impossible), especially at a bathroom (see #1);
5. You may well have to take extreme measures. Based on your description, I would suggest removing the interior wall/celing finishes and the now-wet insulation and using a closed cell spray foam insulation. This is impermeable, will not pass moisture and will exceed any r-value of other products. This may seem extreme (it is) but the moisture, mold and rot will do it for you if you don't. Please note that the roof sheathing must be inspected and replaced if rotted;
6. The earlier suggestion of drilling the 2x6 "mid-ridge" might help if the bottom of the eaves can get a soffit vent like a circular vent in each rafter bay or continuous strip vent installed, and if the insulated upper portions have a channel between the insulation and roof sheating and the main ridge can get a vent (or perhaps a small gable vent with a fan if there is a small attic space at the ridge. But this puts you into step 5 for a better result.

Good luck. This is extremely serious (as I am sure you know)and will be a lot of work to fix right. But if you do it well, your energy costs will drop, and your roof won't rot away. Also, if your recessed lights are going into unconditioned space like the attic floor, they must be air-tight and insulated cans, not standard units.

    Bookmark   December 21, 2006 at 11:01PM
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