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klbf 08-13-2008 08:00 PM

roof ventilation
 
We are putting on a new roof. we have gable vents only no sofitt vents. The roofer suggested putting on a ridge vent as well as 3" diameter sofitt venting. They accidentally put on roof louvers. They will take them off, but said the more ventilation the better and that it will be ok since we have a 12/12 pitch. they have not done the sofitt or ridge ventilation yet. what would be best for ventilation.

Ed the Roofer 08-14-2008 12:56 AM

Quote:

Originally Posted by klbf (Post 148572)
We are putting on a new roof. we have gable vents only no sofitt vents. The roofer suggested putting on a ridge vent as well as 3" diameter sofitt venting. They accidentally put on roof louvers. They will take them off, but said the more ventilation the better and that it will be ok since we have a 12/12 pitch. they have not done the sofitt or ridge ventilation yet. what would be best for ventilation.



Are they filling in the holes from the accidental roof louvre mushroom vents with solid sheathing spanning from rafter to rafter or just bracing a small piece in the location instead?

The Gable Vents need to get closed off to prevent Short-Circuiting of the attic ventilation flowage.

You will not be able to obtain the necessary and required amount of Intake Ventilation from the mini-circle vents.

You need to consider a more efficient product for intake, which should have been considered prior to the roof being installed, which would have left you the option to install the Smart Vent Fresh Air Intake Vent, by DCI Products.

How wide are your soffit overhangs?

With the Ridge Vent providing 18 square inches of NFVA per lineal foot, you would havwe to match or exceed that quantity from the Intake Vents you use.

A 2 1/4 inch diameter provides only 1.50 square inches per vent plug

A 4 1/2 inch diameter provides only 3.00 square inches per lineal foot.

You would need to install 3 of the 4 1/2 inch diameter plugs every lineal foot of the soffit on both sides of the roof to only equal the amount of the Exhaust NFVA.

What wrong with that picture?

3 x 4 1/2 inches = 13 1/2 inches, plus, that would require them to be one hole right next to each other and you would never get enough in place.

Those specs are from the C-Series Under Eave Cornice Vents, also known as Mini-Louver Vents, from Lomanco.

www.lomanco.com/ProductPAGES/CirkVents.html

Ed

klbf 08-14-2008 08:10 AM

ventilation
 
bracing a small piece. (metal) there have been no problems in past with ventilation as far as moisture (mold) etc. would we be better off just keeping gable vents only?


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