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casey_wa 05-04-2006 02:40 PM

Vaulted Ceiling Insulation Problem
Our family room has a large vaulted ceiling. There is bat-fiberglass insulation in the ceiling. We are in the process of getting bids for a composition re-roof. There are ventilation issues that need correcting.

One problem that I notice was when I went into the second floor attic and shined a flashlight down at the top of the insulation for the vaulted ceiling below. There is very little to no gap between the insulation and the underside of the roof sheathing.

I can see how this can create a problem with convection air flow from the eave vents upward to the topside roof vents. What I am looking for is ideas on how to correct or improve this issue. I can gain access from the attic or from the eaves...the eave access would be much easier is expect without dealing with a cramp space, heat and roofing nails poking.

Is there some type of product that can be slid upward from the eaves between the insulation and the roof sheathing to ensure adequate air flow?

Thanks for any thoughts and ideas, Casey

casey_wa 05-04-2006 05:23 PM

Have similar problem with two small (5 wide by 7 deep) peaked roof dormers at the front of the house. The side ceiling is also vaulted. Even though the two dormers have soffit vents there are no other means for air to exit. The roof framing creating separate voids further complicates this issue. Additionally these voids are filled with insulation. Even with ridge venting the insulation obstructs the air circulation. I suppose that a way should be found to vent the dormer roofs?

MJW 05-04-2006 05:45 PM

Get chutes made for soffits. It is made to hold back insulation and let air througn on the top. They are made of foam or cardboard. Install them all the way from the soffit to the peak between most if not all the rafters then cut the sheathing and install a ridge vent. A qualified roofer would know how to do all of this, although you may be installing the chutes yourself.

casey_wa 05-04-2006 08:44 PM

I was thinking kinda the same thing MJW...and really appreciate your response. We are having a pro roofer come in and install a new comp roof. We are still deciding on the use of the can vents or the ridge vent (wondering if the ridge vent is worth the extra $8 per foot).

There is cardboard baffles at the attic and the soffits. It is the space in-between the is a bit tight...maybe it is loose enough, but seems a bit close. With the nails protruding down from the roofing, I was thinking that the card board baffle might be tough to slide up the approx 16 to 18 feet to the attic. I wonder if there are cardboard tubes that might be easier to slide up. But then again, nothing is easy. Thanks again....Casey

redline 05-04-2006 09:05 PM

How wide are the ceiling rafters? (6",8",10",12"...)

MJW 05-04-2006 10:06 PM

If there is some space a ridge vent will work very well. I would definitely opt for the ridge vent on any vault.

casey_wa 05-05-2006 10:55 AM

Redline, the ceiling rafters are 2x8 on 24 inch centers.

MJW, I agree about the ridge vent on a vault...if it goes all the way to the roof peak. However, our family room vault ends at the upper attic above the second floor. It does not stop at the roof peak. I can nearly stand in this attic space that is about 10 feet wide. The roof pitch is 10:12. I am debating the extra cost of using ridge venting ($800) vs can vents since the vault is venting into the upper attic space. If the vault had terminated at the peak then the ridge vent is a must...

redline 05-05-2006 04:47 PM


Originally Posted by casey_wa
Redline, the ceiling rafters are 2x8 on 24 inch centers.

Do you know what r-value is need for your roof (attic)?

If not, then tell what state that you live in and I will look it up.

casey_wa 05-05-2006 10:34 PM

Redline...I live in Washington State, Seattle. Thanks

redline 05-06-2006 04:20 PM

It appears that for a vaulted ceiling it should be R-30 insulation and for an attic area it should be R-38 insulation.

What is the R-value that you have now?

redline 05-06-2006 04:23 PM

You indicated that you are having a "re-roof". Does this mean that you are having another layer put over top of the first layer of shingles or are you having the older shingles removed and new plywood installed?

casey_wa 05-07-2006 10:11 AM

Redline...I will get up into the attic today and check on the thickness of the insulation. Re-roof is having the old single layer removed down to the plywood decking. The only new decking is replacing what is damage. The rood is 10:12 with the single vault of the family room ending at the second floor attic. The living roof is a peaked vault but has a shallower vaulting that creates its own little attic space...meaning, I can remove our second floor built-in bookcase and look into the space between the roof decking and the living room ceiling. I could just be able to crawl over the peak of the living room to the other side within this space underneath the roof sheathing...if I want to, but dont.

redline 05-08-2006 07:56 AM

One possible solution would be to have the roofer create the space (air gap/venting) by by raising (shim) the new roof. This would be more expense for new plywood to cover the roof area.

casey_wa 05-08-2006 09:55 AM

Both the vault and the attic are R-30 insulated. There are batts in the vault and blown for the attic. The attic could use more insulation due to the insultation being disturbed and compacted in places from being up in the attic periodically over the years.

Raising and shimming the roof is not an option since would have to do the whole side of the roof on the backside of the house since it is one large expanse of 20 squares. I have recently read, but not looked into yet, of products that can be used to slide up from the soffit vents between the roof sheathing and the insulation to ensure an air flow channel.

The length of the backside of the house is 65 feet. Inside the family room is 24 feet of vaulted ceiling with a fireplace taking up 6 feet. The remainder is 18 linear feet of soffit to insert some type of air channel...along the 14 feet from the soffit to the attic. The only clear obstructions are the four can lights in the vaulted ceiling.

I am going to explore this closer with a friend having one of us in the attic and the other shining a bright flashlight up from the soffit and see what or any light that can be seen. Maybe there is enough of an air gap between the insulation and the sheathing, I believe it only needs about an inch.

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