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Old 03-15-2010, 04:24 PM   #1
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Attic Ventilation. Just double checking before I start ... :)


Hey all,

I have a house built in 1975 that is 50' x 31.5'. I'm wanting to add more attic ventilation. The current attic ventilation is 2 triangular gable vents and two wind turbines. I live in DFW Texas, and the summers are hellish. lol ... I'm thinking about adding 8 soffit vents (there are none now) after doing some calculations found on the internet. (1 ft for every 150ft) Will the Soffit vents work with my current gable/wind turbine setup??? I don't think it should be an issue, but want to make sure. thanks ...

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Old 03-15-2010, 06:43 PM   #2
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Attic Ventilation. Just double checking before I start ... :)


Gable vents switch off & on from intake to exhaust, meaning if the winds come westernly than the gable facing west becomes an intake and the gable facing east becomes exhaust and visa versa.

Intakes at the eaves "soffit" will always be intake,
exhaust at the ridge "turbines" are almost always exhaust.

Two sources of intake can conflict with one another, the same way two sources of exhaust will.

I would close/block off the gable vents once you install the eave intakes and add additional exhaust. Maybe double what you have now, with out pictures I'm giving an educated "blind" guess.

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Old 03-15-2010, 06:51 PM   #3
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Attic Ventilation. Just double checking before I start ... :)


Is it ever bad to have too much intake with more soffit openings?
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Old 03-15-2010, 09:12 PM   #4
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Attic Ventilation. Just double checking before I start ... :)


I agree with sly for the most part. You can have all the gable, ridge, or other vents up top you want but there just decoration if there is no air coming in from the bottom (soffits). The only part I disagree with and this is only from a budget standpoint (if budget is an issue) is blocking the gable vents off now. Ridge venting is the way to go but if a new roof is in the foreseeable future then soffit and gable vents are at least venting and are way better than you have now which is nothing. When you re-roof, add all the top side vents you want.
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Old 03-15-2010, 10:00 PM   #5
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Attic Ventilation. Just double checking before I start ... :)


http://books.google.com/books?id=Z8a...20NFVA&f=false

http://www.fureyco.com/content/image...ng_The_Air.pdf

http://www.ronhungarter.com/black_mold.html

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Old 03-16-2010, 08:16 AM   #6
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Attic Ventilation. Just double checking before I start ... :)


I guess the question, it appears, is to block the gable vents or not. I'll get up in the attic today and see if the gable vents can fold shut. I suspect they don't .... Lol. I want more ventilation especially with my upcoming radiant barrier, but I don't want to have a moisture problem. Honestly, I've seen answers across the board about mixing exhaust vents. I know for sure not to add ridge vents with other kinds though.
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Old 03-16-2010, 02:22 PM   #7
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Attic Ventilation. Just double checking before I start ... :)


In Atlanta everyone advises leaving Gables when adding ridge vents. (Except the manufacturer of the ridge vents) To me it seems that this is bad advice, as the ridge vents might end up sucking air from the gables rather than from the soffits, so the cool air would not be circulating through the whole attic as intended. Also, wind could be forcing air into the gables, again diminishing the efficacy of the soffits.

It seems logical that the most efficient airflow would be to intake cool air at the lowest possible point (soffit) and exhaust at the highest possible point (ridge).

I plan on testing this by leaving my gable vents in, and blocking them with plastic sheeting, taking a temperature reading at the center of the attic, then removing the plastic and watching the temperature. This will be a few months from now when we get hotter weather. I'll post results here.
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Old 03-16-2010, 02:34 PM   #8
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Attic Ventilation. Just double checking before I start ... :)


Quote:
Originally Posted by echase View Post
In Atlanta everyone advises leaving Gables when adding ridge vents. (Except the manufacturer of the ridge vents) To me it seems that this is bad advice, as the ridge vents might end up sucking air from the gables rather than from the soffits, so the cool air would not be circulating through the whole attic as intended. Also, wind could be forcing air into the gables, again diminishing the efficacy of the soffits.

It seems logical that the most efficient airflow would be to intake cool air at the lowest possible point (soffit) and exhaust at the highest possible point (ridge).

I plan on testing this by leaving my gable vents in, and blocking them with plastic sheeting, taking a temperature reading at the center of the attic, then removing the plastic and watching the temperature. This will be a few months from now when we get hotter weather. I'll post results here.

I don't have a ridge vent system, but it Im trying to decide whether or not to block the gable vents on my existing gable vent/wind turbine set-up after adding soffit vents.
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Old 03-16-2010, 03:33 PM   #9
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Attic Ventilation. Just double checking before I start ... :)


I wouldnt find it necessary to block off your gable vents after adding in the new soffit vents.
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Old 03-16-2010, 06:24 PM   #10
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Attic Ventilation. Just double checking before I start ... :)


Quote:
Originally Posted by echase View Post
In Atlanta everyone advises leaving Gables when adding ridge vents. (Except the manufacturer of the ridge vents) To me it seems that this is bad advice, as the ridge vents might end up sucking air from the gables rather than from the soffits, so the cool air would not be circulating through the whole attic as intended. Also, wind could be forcing air into the gables, again diminishing the efficacy of the soffits.

It seems logical that the most efficient airflow would be to intake cool air at the lowest possible point (soffit) and exhaust at the highest possible point (ridge).

I plan on testing this by leaving my gable vents in, and blocking them with plastic sheeting, taking a temperature reading at the center of the attic, then removing the plastic and watching the temperature. This will be a few months from now when we get hotter weather. I'll post results here.
True to a certain extent, but warm air does rise. It will be caught up in the flow from the gables up the ridge vent.
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Old 03-16-2010, 06:38 PM   #11
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Attic Ventilation. Just double checking before I start ... :)


Quote:
Originally Posted by matjam68 View Post
I don't have a ridge vent system, but it Im trying to decide whether or not to block the gable vents on my existing gable vent/wind turbine set-up after adding soffit vents.
On a scale of 0-10,
ridge vents rank a 9,
pot vents rank a 8,
turbines vents rank a 7,
when properly installed.
The turbines rank lowest because of the mechanical movement some times reversing and sucking wind/moisture into the the attic.

If you install intake ventilation now and have unobstructed air flow from the intake to the turbines they will work, assuming there is enough of them in place now.

As far as blocking off the gable vents, leave the exterior part of them alone and simply block them off from the inside using plywood.


A few years ago I roofed a home that had been rebuilt after burning to the ground, nothing but the foundation was saved.
The fire marshal started off thinking it was burnt on purpose at first, but after investigating the situation he determined the cause for the accelerated fire was due to the roofing ventilation.

This home originally had gable vents period, nothing in the eaves or roof.
When they had the home re-sided they installed intake vents in the soffit.
Years later the re-roofed the home and added pot vents in the roof.
Both times the left the gable vents intact.
When the fire started in the kitchen and went up the wall, once it hit the attic "on a high wind day" with soffet intakes and gable intakes both let winds in at different angles and created an upward surge for the fire.
The fire marshal said the homes damage would have been contained to the back of the home if not for that freak situation.

The mixture of vents did not cause the fire, but, it surely increased the damage caused by the fire.
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Old 03-16-2010, 08:38 PM   #12
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Attic Ventilation. Just double checking before I start ... :)


Quote:
Originally Posted by Slyfox View Post
On a scale of 0-10,
ridge vents rank a 9,
pot vents rank a 8,
turbines vents rank a 7,
when properly installed.
The turbines rank lowest because of the mechanical movement some times reversing and sucking wind/moisture into the the attic.

If you install intake ventilation now and have unobstructed air flow from the intake to the turbines they will work, assuming there is enough of them in place now.

As far as blocking off the gable vents, leave the exterior part of them alone and simply block them off from the inside using plywood.


A few years ago I roofed a home that had been rebuilt after burning to the ground, nothing but the foundation was saved.
The fire marshal started off thinking it was burnt on purpose at first, but after investigating the situation he determined the cause for the accelerated fire was due to the roofing ventilation.

This home originally had gable vents period, nothing in the eaves or roof.
When they had the home re-sided they installed intake vents in the soffit.
Years later the re-roofed the home and added pot vents in the roof.
Both times the left the gable vents intact.
When the fire started in the kitchen and went up the wall, once it hit the attic "on a high wind day" with soffet intakes and gable intakes both let winds in at different angles and created an upward surge for the fire.
The fire marshal said the homes damage would have been contained to the back of the home if not for that freak situation.

The mixture of vents did not cause the fire, but, it surely increased the damage caused by the fire.
What's an "intake vent at the soffit?"

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