12:51PM | 04/23/05
Member Since: 04/22/05
2 lifetime posts
I will try to make this as clear as possible.

Well, I just finished my new roof (tore 2 layers of old shingles off, added GAF Timberline 30 Arch shingles). I also added a ridge vent the entire length of the roof (73' long).

My next step is to replace all the aluminum on the windows, doors, soffits and gutters. I decided to start ripping some of the soffits today to see how the house vented currently. Aluminum soffit was used with 1 vented piece for every 3 solid. When I ripped the solids there was plywood running the entire length of the roof. Wherever there was a vented aluminum panel, a 6"x6" hole was cut into the plywood and I could see up into my attic (I have a ranch).

Since I would like to install new soffit (either vinyl or aluminum where each piece has a vent in the middle), what would be the easiest way about this?

I could use a circular saw set to the depth of the plywood and cut a strip out of the plywood the entire length, but that would be difficult to do upside down, especially where I have an area where the soffit climbs to 20+ feet high.

I also thought of just pulling all the plywood, then just covering it with the new soffit. This would basically leave me the entire 16" of overhang around the house to be totally open to the outside with only the soffit pieces blocking it. Would this be acceptable?

I installed a GAF cobra vent across my entire roof (73' long minus 1.5' at each end, or 70' of vent). According to the GAF webpage, it has an area of 16.9 sq inches of NFA (net free area) per foot, or 1183 sq inches in my case for air leaving the attic. I have read that your incoming area should always be greater than the outgoing, meaning I need more than the 1183 sq inches.

I plan on using a Triple 4" Center Vent for soffit (see following link)

Per that page, it only provides 1.56 sq inch per foot. I have 73 feet of soffit in the rear of the house, and 45 feet in the front. This would equate to only 184 sq inches of incoming air. This seems very small. The soffit vents on the GAF webpage are only 1.75" wide and are supposed to flow 82 sq inches per 8 feet of vent.

Would this still hold true if I totally removed all the plywood under my old soffit, thus having 16"x73' feet of total opening in the rear and 16"x45' in the front under the new soffit?



01:16PM | 04/23/05
Member Since: 01/30/05
361 lifetime posts
From what I'm gathering from your post, your previous attic system did NOT have a ridge vent, and your eves were open (sofit vents).

Now you have defeated the previous open eve system by adding a ridge vent.

Whether or not you are in a hot/cold climate, and especially if you are in a heating season climate, you have now taken what was a cold attic that used convection to move air and keep the attic cold during the heating season (and I'll assume that the insulation was only on the attic "floor") and will vent out of the ridge vent your heat from the home in the winter (you'll have the first roof to melt snow in the neighborhood)!

If this is the're going to need to now vent between the trusses/rafters an enclosed system from each sofit/eve opening up to the ridge vent and insulate around it to keep your roof cold. When it is hot outside your sofit vents will have limited ability to draw cooler air from outside now as well with this ridge vent if you don't channel the sofit vents to the ridge vent.

Expect condensation on your upper ceilings whereever a ceiling (attic floor joist) exists come this winter, dark streaks, mildew in upper bathrooms, and lots of nail pops now if this is the case.

Additional information as to the cubic feet of your attic (square footage, roof pitch, height, etc.) will be needed to calculate the size of the openings etc. to determine the CFM required to ventilate the attic.

Your location /climate zone will be helpful as well.


03:05PM | 04/23/05
Member Since: 01/30/05
361 lifetime posts
read through these posted strings completely. some have useful information which will help you determine the cubic feet of your attic area, some regards to various climate zone issues regards to attic venting.

The words that were escaping me in my prior post regards to "channeling" the air flow from your sofit vents to your ridge vents, were BAFFLES (usually made out of foam).

Your roof ridge vent can only vent the amount of air that comes in through the lower sofit/eave vents. It will not create a vacuum effect in your attic.

Also may have some useful information for you, and a nice zone climate tool regards to specific issues in your area.

See if those posts and some related links posted therein are helpful.


03:46PM | 04/23/05
Member Since: 04/22/05
2 lifetime posts
I live in central NJ, so it does get quite cold here.

My attic is roughly 32'x73', with a height of approximately 4 feet in the middle (not a very steep roof at all).

My current 16" soffit overhang consists of many solid pieces, then 1 vented piece. For example, the entire rear soffit of 73 feet in length has only 5 vented pieces. Under the aluminum soffit is 1/4 plywood, and a 6"x6" hole cut under the 5 vented soffit pieces.

My attic currently has insulation across the ceiling joists (I own a ranch), but no insulation along the roof rafters. I planned on pulling back the insulation at the top plate and installing the 48" long Owens baffles, then pushing the insulation back against the baffle. This would allow the inflow into the attic.

My concern is having enough inflow area since I already added 70 feet of ridge vent.



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