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Old 10-14-2010, 01:59 PM   #1
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New roof with ridge vent. Enough venting???


Location: North Texas
Climate: averaging 95 F most days for 3-4 months each year.

I recently had a new roof put on with about 30 feet of ridge venting. I have read about not mixing ventilation methods, so had one small exhaust fan removed when the new roof went on. I have soffit vents avery 4 feet. They are approx. 6"x12" and seem free of insulation/other debris.

Should this provide enough venting?

One time (not at band camp) my fan motor died on the attic exhaust fan and the temperature in the attic shot up to 150+ degrees. With the fan installed it peaks at 118 or so.

Would adding an intake fan low in the attic be useful, to push in cooler air and force the hotter air out the ridge vent? Or would that end up blowing the cooler air out the soffits as well and creating chaos in the air patterns?

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Old 10-15-2010, 12:17 AM   #2
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New roof with ridge vent. Enough venting???


hi this is Brandon with let it reign construction and my question is how much living space do you have and what is the weather like ware you are at this is some thing to look at and see if the fan is a must for you

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Old 10-15-2010, 12:30 AM   #3
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New roof with ridge vent. Enough venting???


Living space is irrelevant to attic space and he said where he was from and average temps.Knowing the sq footage of attic is important as well as pitch,height,etc.I would increase intake,and no to the attic fan.Need to know more info to help calculate ventilation requirements though.
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Old 10-15-2010, 12:55 AM   #4
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New roof with ridge vent. Enough venting???


What I meant to say is living space has nothing to do with attic ventilation requirements.
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Old 10-15-2010, 10:10 AM   #5
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New roof with ridge vent. Enough venting???


johnk,
Actually, the code requires 1 sq ft of venting per 150 sq ft of living space, so there is a connection.
Reduce the venting to 1 sq ft per 300 sq ft of living space if the venting is both top and bottom of the roof.
The ridge vent should have a rating on it to say how many sq ft of venting it supplies per foot of length.
One third of the required venting (min) should be in the top third of the roof.
And you can't have too much venting.
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Old 10-15-2010, 12:45 PM   #6
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New roof with ridge vent. Enough venting???


30' might or might not be enough. The minimum calculations are based upon the square footage of the attic floor space, the recomended calculations take pitch into account and are based upon cubic footage. Intake is also a must when using ridge vent, without intake an infinite ammount of ridge vent is useless. All vents work better with an intake, a ridge vent simply will not work without an intake.

jlhasip, I'd like to see that code in writing where the words "living space". I've never once read living space. If I had a 2,000 square foot foot print but had 4 stories making it 8,000 square feet of living space; seems flawed.


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Old 10-15-2010, 12:47 PM   #7
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New roof with ridge vent. Enough venting???


Your Codes may be different than ours in the U.S.
From the 1994 UBC: Attic Ventilation
Enclosed attics and enclosed rafter spaces formed where ceilings are applied to the under side of roof rafters shall have cross ventilation for each separate space per UBC Sec. 1505.3. From: http://www.mcvicker.com/resguide/page010.htm
From the 2009 IRC: R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow.
R806.2 Minimum area. The total net free ventilating area shall not be less than 1/150 of the area of the space ventilated except that reduction of the total area to 1/300 is permitted provided that at least 50 percent and not more than 80 percent of the required ventilating area is provided by ventilators located in the upper portion of the space to be ventilated at least 3 feet (914 mm) above the eave or cornice vents with the balance of the required ventilation provided by eave or cornice vents. As an alternative, the net free cross-ventilation area may be reduced to 1/300 when a Class I or II vapor barrier is installed on the warm-in-winter side of the ceiling. From: http://publicecodes.citation.com/ico...9_8_sec006.htm
Outside front porches, back porches and attached garages require ventilation if a ceiling material is applied. No distinction about living spaces, (just attic spaces), though the whole idea of ventilation is to get rid of condensation from the living space and asphalt shingle manufacturers require it for most of their products.

Do not go with the power fan idea. In coastal areas you can have too much ventilation (even meeting the minimum code) but for your location you could add more soffit venting. With your 6x12 vents = 28sq.in.NFVA divided by 4’ = 7sq.in.--- could be 9sq.in. if figuring 150. Where are the soffit vents located in relation to the barge board?

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Old 10-15-2010, 07:22 PM   #8
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New roof with ridge vent. Enough venting???


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Originally Posted by jlhaslip View Post
johnk,
Actually, the code requires 1 sq ft of venting per 150 sq ft of living space, so there is a connection.
Reduce the venting to 1 sq ft per 300 sq ft of living space if the venting is both top and bottom of the roof.
The ridge vent should have a rating on it to say how many sq ft of venting it supplies per foot of length.
One third of the required venting (min) should be in the top third of the roof.
And you can't have too much venting.
So like grumpy said,I would like to see this code you speak of,doesn't make sense.
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Old 10-15-2010, 07:26 PM   #9
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New roof with ridge vent. Enough venting???


http://www.askthebuilder.com/B335_Ca...of_Attic.shtml This not a copy of code but general knowledge. http://www.articlesbase.com/home-imp...s-1866882.html heres another and one more http://www.renovation-headquarters.c...alculation.htm

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