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-   -   Attic venting - Ridge vents or fans? (http://www.diychatroom.com/f9/attic-venting-ridge-vents-fans-21400/)

jebmke 05-24-2008 12:43 PM

Attic venting - Ridge vents or fans?
 
Mid-Atlantic region (hot summers). House does not have ridge vent but gable fans instead. These are old fans and one recently died. It seems that there is a debate over active ventilation (fans) vs. ridge vents. I was thinking about replacing the electric gable fans with solar roof-top fans to reduce the noise and power consumption.

An alternative would be to have a roofer come in and install the ridge vents that were left out by the original builder.

Any comments on ridge vents vs. solar? We do have fairly extensive soffit vents to provide the intake.

Ed the Roofer 05-24-2008 12:58 PM

The drawbacks to the solar units are not only their limited potential to the sun exposure, but their limited CFM ratings per unit. You would probably need multiple solar units to adequately perform.

Ridge vents works passively and also ridge vents with external exterior wind deflecting baffles have increased performance even with a moderate 3 mph wind force.

As long as you actually do have the proper amount of intake NFVA ventilation calculated, then either would seem to be a workable solution.

Ed

johnk 05-24-2008 01:00 PM

I would go ridgevent all the way,IMO solar units would be expensive and you would probably need quite a few.Ridgevent is hidden and no power needed and will provide you with adequate exhaust.You must then plug your gable vents.

jebmke 06-23-2008 10:06 AM

Follow up question for Ed. I did some homework and everyone agreed that ridge vents were the way to go. I had a contractor (licensed roofer) come out an install Shinglevent ridgevents. HOwever, I think there is one section installed incorrectly. I'd like your opinion, if possible.

The ridge runs North-South so the roof faces east and west. When the house was originally built, on one section of the ridge, the sheathing had not been originally cut back from the ridge to create the vent opening. The roofing contractor who came in last week to install the shinglevent only cut the hole on the east side. It seems to me that this is going to be less than adequate for venting. Won't the ridge beam prevent good airflow from the soffits on the west side and block any outward flow from the west side. The east side cut is "generous" but based on what I have read, the air needs to flow up from the soffit vent along the sheathing to the vent opening to create a good flow along the roof. The presence of the ridge will block the flow from the west side (which will be the hottest side).

Am I missing anything?

The contractor made some excuse like the ridge vent will lay too flat but in the end he has agreed to come out an cut the west side vent in the sheathing. My only concern is that the east side may be too wide an opening when he recenters the vent.

Ed the Roofer 06-23-2008 12:35 PM

Since you used the Shingle Vent II Ridge Vent, I suggest that you go to the www.Airvent.com website and get a copy of the installation instructions.

They specifically state how the ridge vent product is to be installed, and have an alternative dimension for installation when a ridge beam is present.

Since you provided no precise dimensions cut, nor provided a photo with tape measure for reference, this is the best that I can suggest at this time and have it available for when he comes back.

By the way, every case of the Shingle Vent II has a written page of installation instructions included inside the box.

Ed

jebmke 06-23-2008 01:12 PM

thanks for reply
 
1 Attachment(s)
I did see the installation instructions.

Attached (I hope) is a photo of the cut made on the east side. The cut made on the east side is approximately two inches. The west side of the beam has no cut at all. I guess I am interested in two things:

First, am I correct in my assessment that the lack of a west-side cut will diminish the effectiveness of the ridge vent?

Second, the east-side cut being two inches, if they make a cut on the west-side to open up that side, is there any issue with the east side being somewhat over-sized relative to the installation guide?

Thanks again.

Ed the Roofer 06-23-2008 02:22 PM

I would tend to think that the bottom of the ridge board would slightly at least, if not more, interfere with the proper flowage, or fluid dynamics, of the air from the eave on that side to escape at its optimum efficiency.

The 2" slot, although wider than recommended, should not pose a great threat for water/snow entry from blowing winds, if the top of the shingles where the ridge vent connects to them, has a bead of geocel sealant installed, but other sealants will do nearly as good of a job, just as long as it is not real cheap inferior grade and not roof cement in a caulking tube.

The actual width of the ridge vent, from outside of each exterior baffle measurement to the other, is at or around 14", so it should still have enough coverage.

Ed

His User Name Is: Apple Roof Cleaning
with the spaces in the name. He has posted on this forum 16 times, so is not a regular, but you can try his PM box or e-mail if he has it set up to accept them.

parkerfairfield 06-27-2008 08:08 PM

Quote:

Originally Posted by Ed the Roofer (Post 132976)
I would tend to think that the bottom of the ridge board would slightly at least, if not more, interfere with the proper flowage, or fluid dynamics, of the air from the eave on that side to escape at its optimum efficiency.

I would definitely think that it'd have "an impact" ... but how much ... that's anyone's guess.

On a scientific level, one could get a fog maker or smoke bomb and try to observe the differences between the side with the cut vs. the non-cut side. (bring extra water as it'll get hot 'observing').

On a practical level, there are multiple options. Your end objective is really what will drive you down any one path ... and of course as I 've never met you, I've no idea.

On a 'did the roofer do his job right', you could get with the representative...

On a 'is it going to leak' front, you can poke your head up there when it's raining (spraying a hose is NOT the same as a rain ... and is not recommended as the force of the water can often create a leak which did not exist previously.)

On a 'is my west side roof field going to degrade more quickly than it would have, had the roofer followed the instructions', I'd guess no. As you've described your roof system, with the gable vents plugged (they are, right?) there is going to be a LOT of air movement on a hot day up the west side.... and as your beam isn't a 2x20 or something extreme like that ... the idea that the hottest air (which is obviously at the ridge) is going to be occluded by the 2x4 ... well, I don't think that's going to happen. The air is going to move in the correct way ... and while you may bake a one inch wide strip at the very ridge of your west roof ... that section is covered by the airvent.

On a 'do you wanna worry the roofer' - yeah, if he's licensed, he should worry. I know I'd be over the explaining my thoughts, etc. If you didn't buy my logic, then I'd be offering to cut back another 5", stripping in a 6" wide piece of OSB, felting, and then putting in a few courses on the east side ... and then following the directions for the west side. IF YOU HAVE older shingles - then I'd be explaining there's going to be a color discrepancy - and I'd have you sign a color waiver - while giving you a 5yr no leak warranty for the 'repair' that I'd just performed.


Peace.

(Greets Ed)

Ed the Roofer 06-28-2008 12:27 AM

Greetings back at you Parker.

I already said Hi to you on the other forum you just posted in regarding the trade show.

Ed

comp 06-30-2008 02:43 PM

i want ridge vent,,,and a fan i can contol :thumbsup:

Ed the Roofer 06-30-2008 07:36 PM

Quote:

Originally Posted by comp (Post 134872)
i want ridge vent,,,and a fan i can contol :thumbsup:

If you had both, a PAV and continuous ridge Vents installed and operational, you would screw up the ventilation flowage, big time. Unless you were referring to a whole house fan, to exhaust the interior heat into the attic and out of the ridge vents.

Ed

parkerfairfield 06-30-2008 11:24 PM

Actually Ed, as I recall, one CAN put (but WHY?) an additional fan within 3 feet of the ridge and not screw up the venting with ridge vent.

Where most DIYers / numbskull roofers screw up is not closing off the gable vents.

Ed the Roofer 07-01-2008 12:11 PM

Parker,

I think you misread the instructions from Air Vent Corp., if that was your source.

They state to not install any additional ridge vents on any plane that are more than 3 feet difference in elevation, unless the attic chambers are sealed off from each other.

Specifically, in their Hip Roof Brochure, which discusses the issues pertaining to PAV's, they state to NOT use contrasting Exhaust Ventilation Systems, as they would short-circuit the air flowage. This would be even more evident, if the PAV were closer to the ridge vent.

If you have a different source, I would be pleased to review it.

Ed

parkerfairfield 07-01-2008 02:10 PM

Quote:

Originally Posted by Ed the Roofer (Post 135147)
Parker,

I think you misread the instructions from Air Vent Corp., if that was your source.

They state to not install any additional ridge vents on any plane that are more than 3 feet difference in elevation, unless the attic chambers are sealed off from each other.

Specifically, in their Hip Roof Brochure, which discusses the issues pertaining to PAV's, they state to NOT use contrasting Exhaust Ventilation Systems, as they would short-circuit the air flowage. This would be even more evident, if the PAV were closer to the ridge vent.

If you have a different source, I would be pleased to review it.

Ed

You're right ... I recall what you've written now.... less that I misread, more that its been too long since I've read it.

Thanks Ed!

bob22 07-03-2008 08:46 AM

Not to hijack the thread, I think this is relevant: what is the best way of closing off the gable vents when a ridge vent is a retrofit? Would metal duct tape applied to the inside of the gable vent last?
tia,
Bob


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