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soffits blocked, but other vents there


Peanut
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So I see this 1946 house here in FL today. It still has the old gable vents. It's a very small house, barely 1200 sq ft. Someone added a ridge vent. I presume that it has the soffit vents, but after being in the attic, I see that the insulation is blocking the soffit. I see no daylight at the eaves, and looking with the flash, see no baffles and insulation is right to the eaves.

The roof is 2.5 years old, and so far shows no real sign of deterioration. I understand that the ridge vent is meant to work with the soffit vents, and I understand that the ridge vent should not be used in conjunction with gable vents. But how is this bit going to work with no soffit vents and only the gable and ridge? Am I missing something? Was this done on purpose?

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Hi,

Obviously, whoever the roofer was who installed the ridge vent doesn't understand why/how ridge vents are there - he just installs them. He probably never bothered to educate the homeowner about the need for good airflow from the soffits to the ridge or explained why the gable end vent will defeat the soffit vents.

Right now, you're pulling air from the gable end vents. If you close them without opening the soffits, you'll increase the amount of moisture-laden air pulled into the attic from the home. If they want it to work correctly, they need to close the gable end vents and adjust that insulation at the wall plates to facilitate good airflow.

ONE TEAM - ONE FIGHT!!!

Mike

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Alex, the other way to correct that blocked soffit problem is to install baffles at the soffits to allow air flow past the insulation. If you aren't familiar with baffles you can see them at any home improvement store. They're cheap, but installing them isn't going to be a lot of fun. As it is that house has air outlets, but no air inlets; 1/2 a ventilation system.

Brian G.

"Baffled" By Numbskulls Who Block the Soffit Vents [:-dunce]

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So there is no good way to correct this, other than installing the baffles. The HVAC ducts prevent access to much of the attic space. No, it wouldn't be fun. My client poked his head up into the attic as I sat on the ceiling beam, and I explained the venting system to him. He saw for himself that there was no daylight at the eaves, and saw the ridge vent.

I am writing the report now. I believe the only thing I can do here is recommend the proper thing (baffles), no matter the PITA to install. It would have been better to have not bothered with the ridge vent! Just left the old gables as they were. Maybe added a non-powered turbine vent or something....dang.

That's the first time I have seen the soffit vents covered (I have been lucky). Thanks guys!

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Originally posted by Chad Fabry

I'd seal off the ridge vent. Remove it and shingle the ridge with caps. It'll take like an hour and cost 40 bucks. It's been working with gable vents for 50 years...why screw with that?

I wouldn't recommend changing a thing unless I could see a problem that was the result of the existing set up.

It ain't broke.

- Jim Katen, Oregon

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I thought about the ridge vent thing--removing and shingling. But I think I will take the conservative approach--wait and see. I discussed this with my client. Told him that the roof should be inspected every year, and the condition of the shingles monitored, as well as an attic inspection (there are some rafters pulling from the ridge board anyway). See what happens, if anything. He doesn't plan to keep the house--sell it in a couple of years (it's some else's problem, he says). I will make darn sure that I am covered here, though! I'm nearly done with the report--think I will review my comments in that area....

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Gable vents basically work by providing cross ventilation.

Ridge vents along with eave vents utilize the process of convection.

A closed gable vent and blocked eave vent/rafter bays, with only an opening at the ridge vent can cause your attic not to ventillate properly. Along with moisture/mold/ice damming problems it can also cause a negetive pressure effect in the summer which can cause conditioned air to leak into the attic.

Try reading

Structure, Interior and Roof Inspections of Existing Dwellings by Michael Casey and Kevin O'Mally

Housebuilding by R.J. Cristoforo

These will give you a basic understanding of how and why.

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Originally posted by Haubeil

I was not aware that a ridge and gable vent combination was bad...or let say, does not provide adaquate ventilation.

The conventional wisdom is that gable-end vents short-circuit the "wash" of air that's supposed to take place with a combination of soffit vents and ridge vents. In reality, no one knows exactly how any ventilation system will behave until it's installed and tested under a variety of weather conditions.

The best way to learn how a particular ventilation system will work in the future is to study how it's worked in the past.

Is there a publication that lists all the variations ventilation combinations and scenarios...and the respective pros & cons?

I believe that Certainteed has a excellent ventilation manual on their site.

- Jim Katen, Oregon

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Originally posted by Haubeil

I was not aware that a ridge and gable vent combination was bad...or let say, does not provide adaquate ventilation.

Is there a publication that lists all the variations ventilation combinations and scenarios...and the respective pros & cons?

Thanks,

Haubeil

Go here: http://www.airvent.com/professional/education.shtml

Take the online ventilation course. It's free.

OT - OF!!!

M.

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  • 2 weeks later...

Hi Mr. Cat,

Don't know about where you are, but here those will only pull more moist air and fungal spore into the attic through the other gable end vent(s). I've gone up into attics where those are installed and found that the side of the rafters/trusses away from the end of the attic where the fan was installed was discolored and fungi was growing on the framing and underside of the roof. It's definitely not a good solution in this temperate climate with our long rainy seasons, and spore-rich atmosphere.

OT - OF!!!

M.

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Nice as an aside to inform the client, but with no visible signs in the attic after 2.5 yrs of use = no problem. Also, I'm not sure what adding baffles w/out soffit ventillation will do (unless it is an old balloon framed structure which may allow air to be pulled up and through). In NE, I would include a picture w/basic fundamentals of attic ventillation & recommend a continuous soffit vent be installed. Basically this would entail cutting a continuous channel & the soffit (if none present). As an aside I would mention the necessity of each bay being equipped with a soffit vent (ideally). This would be necessary if the soffit was not wood & could not be channelled, then individual vents would need to be added @ each bay. All CYA in my opinion. If this were my own home I'd be taking the wait & see approach, but legally I'm more comfortable with recommending adequate soffit ventillation be added.

Only caveat I'd include would be the difference in ridge venting systems. Baffle type (W in cross section) exceeds cheaper mesh type ridge vent systems. Inadequate ridge vent will allow wind driven rains into attic. If your going to recommend a product, this would be a far superior/minimal extra cost addition.

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  • 3 years later...
Nice as an aside to inform the client, but with no visible signs in the attic after 2.5 yrs of use = no problem.

Not necessarily. What if the existing owner is the only one living in the home. What if the buyer rents the house to a group of college cheerleaders women. All of the sudden, there's gonna be a whole lot more moisture introduced into the box.....

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