# Vinyl Perf Soffit over Wood - No Vents



## Roofmaster417 (Jun 9, 2010)

I have never been a fan of vinyl anything but siding, If you can afford it go with continuous.


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## Gary in WA (Mar 11, 2009)

I agree with RFN, above. But if you have to use vinyl...... The perf sections are only +-4.5 sq,in. per ft., so the soffit would need to be 24" deep from the fascia to house to get the required 9 NFVA per ft. to match 1/2 the ( baffled hopefully) ridge vent (18 NFVA) for each side of the roof. http://files.buildsite.com/dbderived-f/owenscorning/derived_files/derived92755.pdf

http://www.oikos.com/esb/30/atticvent.html

I would pull wood soffit boards at the fascia to accept the continuous strip vent, add blocking for the vinyl "J" channels and cut the old to fit, Fig.s 63-71; http://www.vinylsiding.org/publications/0804_VSI_2007Manual.pdf

The con. vent needs to be next to the fascia to get optimum air pressure, not close to the house, page 616; http://books.google.com/books?id=Z8...page&q=attic airflow with gable vents&f=false

No fear on weakening the roof, soffits are usually non-structural. Your figure sound off..... Compare to this; http://www.airvent.com/homeowner/products/intakeSoffit-specs.shtml

Gary


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## nickelshine (Dec 13, 2010)

Thanks Gary, great information. My soffit is small, maybe a 6" width, so it sounds like the continuous vent is the way to go. While I was thinking to reuse the existing perforated vinyl if possible, you certainly made clear the more important requirements.


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## Roofmaster417 (Jun 9, 2010)

Well GBR in WA,I have to admit thats some impressive stuff.:thumbsup::thumbsup::thumbsup::thumbup:


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## Gary in WA (Mar 11, 2009)

RM, thank you. Feel free to use them when-ever.

Nickelshine, glad we could help! Any other questions, there are a lot of roofers on this forum that can help, just ask away.....

Gary


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## Roofmaster417 (Jun 9, 2010)

Thanks GBR in WA....,but I am starting to build my album under my profile, check it out.


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## beerdog (Dec 10, 2008)

Gary...do you have a picture of a combination soffit and continuous vent installation. I have ot do this same project on a 1foot soffit overhang. My overhang has vented soffit over the original plywood soffit. Someholes are drilled in the wood but I know it is not enough.


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## Gary in WA (Mar 11, 2009)

Sorry, no pictures. Just add framing dropped off the rafter/wall to the elevation you need. Install a 2x running with the cont. vent, next to, for a soffit nailer as well; http://books.google.com/books?id=E5...epage&q=structural ridge roof framing&f=false

Gary


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## nickelshine (Dec 13, 2010)

Spoke with my first roofer about an estimate for ridge vent, continuous soffits vents and two bathroom exhaust vents. Well, he never heard of continuous soffits vents. I tried to explain the concept. Even fired up the internet and showed him the product. He said that he was not interested in learning to install the vents on the job, and decline to estimate my work.

Is this a east coast/PA venting ignorance that I should expect from others?:huh:


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## nickelshine (Dec 13, 2010)

nickelshine said:


> Spoke with my first roofer about an estimate for ridge vent, continuous soffits vents and two bathroom exhaust vents. Well, he never heard of continuous soffits vents. I tried to explain the concept. Even fired up the internet and showed him the product. He said that he was not interested in learning to install the vents on the job, and decline to estimate my work.
> 
> Is this a east coast/PA venting ignorance that I should expect from others?:huh:


Second roofer was more open to the continuous soffit install, but also suggested the option to install perforated vinyl the entire length instead. He seemed to feel that would be even better than the say an Airvent continuous soffit. I believe from the responses above this may be incorrect, and the continuous would still beat the entire length in perforated vinyl...

- Soon to install a 34' ridge vent @ 18" NFA = 612" or 4.25' NFA for ridge.
- Soffit width (one side) = 37' x 6" - With 37' of C-soffit @ 9" NFA per ft = 4.625" total, after including both sides of the house. Seems slightly better than 50% intake :thumbup:

- Perf vinyl @ 4.5" NFA per ft, so total vinyl would only be like 333" or 2.3' NFA intake - not enough intake even with the full length of perfed vinyl...

Have I passed?


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## Gary in WA (Mar 11, 2009)

Yep! "The perf sections are only +-4.5 sq,in. per ft., so the soffit would need to be *24" deep* from the fascia to house to get the required 9 NFVA per ft." From post #3. You always want equal or slightly more intake than exhaust or the negative pressure will pull gas flames, house conditioned air, etc. first, rather than soffit air.

Gary


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## jmiller (Nov 19, 2010)

nickelshine said:


> Have I passed?


Did you calculate the needed ventilation for an attic your size? The ridge vent may not need to be continuous to get the minimum exhaust, which solves the problem of lack of room for intake if you can leave some uncut. It's better to have more intake than exhaust, than it is to have 'continuous' ridge vent, so long as you satisfy codes.


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## beerdog (Dec 10, 2008)

Isn't the intake volume supposed to be equal to or greater than the exhaust? Sounds like the contractors are recomending what is best for them, not you. My experience so far when dealing with roofers is that the only ones who understand ventilation are the ones on these discussion boards.


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## nickelshine (Dec 13, 2010)

beerdog said:


> Isn't the intake volume supposed to be equal to or greater than the exhaust? Sounds like the contractors are recomending what is best for them, not you. My experience so far when dealing with roofers is that the only ones who understand ventilation are the ones on these discussion boards.



Yes, after only two estimate visits and trying to explain what I want, I feel like I am being a difficult customer. Maybe a "Ventilation Snob" even ... Just trying to educate myself on the site; figured they would already be aware of this info.


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## nickelshine (Dec 13, 2010)

jmiller said:


> Did you calculate the needed ventilation for an attic your size? The ridge vent may not need to be continuous to get the minimum exhaust, which solves the problem of lack of room for intake if you can leave some uncut. It's better to have more intake than exhaust, than it is to have 'continuous' ridge vent, so long as you satisfy codes.



The attached image is the suggested (50/50 NFA @ 150) ventilation for my attic space. So this would work. But more is better if available, right? What if I wanted to maximize my full soffit intake area... i.e., run it the full 37' on each side of the house instead of just the 26'. So, instead of 52' of intake I go 72' (almost the entire length). That would of course up the ridge vent length too. Again I have approx. 37' of ridge to work with. So a 30' ridge vent seems to work well...?

Also I figure if I go with the 60/40 vs 50/50...

72' (INTAKE) x 9" NFA = 648" NFA
30' (EXHAUST) x 18" NFA = 540" NFA

648" NFA (approx. 60% soffit)
+ 540" NFA (approx. 40% ridge)
________
= 1188" NFA

That's 9 total pieces of Continuous Soffit Intake Vents - 9 sq.in./foot NFA 
(4.5 each side) - OR - 648" NFA / 9 sq.in./foot NFA = 72' / 8' pieces = 9 total vents

I THINK :huh:


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## beerdog (Dec 10, 2008)

There are many many threads on attic ventilation. Based on pro commentsit sounds like it is very common for roofers and estimators to not be knowledgeable about ventilation.


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## Gary in WA (Mar 11, 2009)

NS, you need to have soffit vents across *every *rafter bay to move the heated air with moisture from the rooms below. Otherwise there will be dead air spots that will get condensation on the roof, framing or insulation. The 150/300 rule is an older one, if you ventilate on a 1/100, you are still fine. 
Working backward;

37 x 9 int. = 333 / 144" = 2.31 x 2 sides = 4.63 total int. + 4.63 exh. =* 9.26 * total 

37 x 18 exh. = 666 / 144" = 4.625 exh.

Gary


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## jdmorman (May 28, 2012)

*Resolution?*

Over the weekend I discovered that our house, built in 1986 and just purchased the week before, has exactly the same problem that nickelshine described: vinyl siding covering solid wood soffit, so no ventilation.

I'm curious to know: did you solve your problem?


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