Latest Discussions : Roofing & Siding

magnumPA

06:04PM | 06/21/04
Member Since: 06/20/04
1 lifetime posts
I'm having a house built and they've just shingled the roof including the caps. But they haven't installed any ridge vents. I know we are getting continuous ventilated soffit, but it seems futile if the heat and moisture have no where to escape at the top. Ridge vents are listed as a standard feature in the builder's plan. But on the particular model we are having built, the roof has several sections at various heights with dormers and shed roofs and valleys, oh my! The highest point of the main section only has about 4 ft of actual ridge. And the other large sections are separated by valleys. Does each section have to be ridge vented? Would a couple powered vents remove the excess heat more effectively? I've considered calling the builder, but I don't want to jump the gun. Is it possible or remotely logical to put ridge vents in after they've finished shingling? I've done my fair share of general construction in the past 20 years. And I've always been under the impression that the ridge vents go on before the last courses of shingles. But that was in PA. Maybe they do things differently here in SW FL. Any input is much appreciated.

-M.

homebild

07:11PM | 06/23/04
Member Since: 01/28/03
693 lifetime posts
Poster asked:

" But on the particular model we are having built, the roof has several sections at various heights with dormers and shed roofs and valleys, oh my! The highest point of the main section only has about 4 ft of actual ridge. And the other large sections are separated by valleys. Does each section have to be ridge vented? Would a couple powered vents remove the excess heat more effectively? I've considered calling the builder, but I don't want to jump the gun. Is it possible or remotely logical to put ridge vents in after they've finished shingling? I've done my fair share of general construction in the past 20 years. And I've always been under the impression that the ridge vents go on before the last courses of shingles. But that was in PA. Maybe they do things differently here in SW FL. Any input is much appreciated."

Bottom line is that ridge vents are not always the best vents.

Ridges that are too small to vent the full attic also do not help in venting.

Sometimes gable vents, power vents, turbine vents or other vents are the BEST vents under different circumstances.

And what your were used to in Pennsylvania has little to do with what happens in Florida.

All that said, roof vent theory says that for every 100-150 sq ft of attic space you need at least 1 foot of vent.

Do the math.

Figure it out.

Vent to attic floor space is the key.


Piffin

07:06PM | 06/29/04
Member Since: 11/06/02
1278 lifetime posts
That formula of 100-150 floor spacew for every fot of vent is correct, but that is for each foot in at the soffit and out at the ridge or at a power vent, or at gable vents. It can do almost no good to allow air in at soffits if no exhaust is allowed at the ridge.

But....

There are two reasons for venting attics. One is to allow heat to escape so shingles can enjoy a slightly longer life. The other is to allow moisture to escape so that it doesa not condense on the interior of the attic spoace and cause rot or signs similar to roof leaks in the ceilings. The altter is more common in cold climates while the former is the more pressing need in southern climates.

if there is a good vapour barrier and adequate (R40 or so) then there is less need for attic venting.

This is a part of building science that has seen many arguments and has many variables. Your local codes enforcement people and the builder may have already planned for this or the builder may be lacking in understanding. There are many possible designs that would make this procedure OK, and others that would make it completely unacceptable. best to simply ask him about it in an unchallenging manner, and possibly ask the building inspector separately as well.

Excellence is its own reward!




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