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ridge vent / gable vent help

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26K views 53 replies 17 participants last post by  TimelessQuality  
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#1 ·
have a customer who just goyot a ridge vent. Currently have soffits ,gable vents and attic fan. Sshould they cover the gable vents? I would think the gable vents will now disrupt air flow. Home is in north east.
 
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#5 ·
The ventilation manufacturers and most widely accepted ventilation studies and theories show that the gable vent air flowage would interfere, also know as Short-Circuit the current soffit to ridge ventilation flowage.

It is a recognized short-coming by mold remediation companies that by having competing types of upper air exhaust systems, the probability of mold growth is increased and is recommended to cover up the gable vents when their is a properly functioning soffit intake flowage and ridge vent exhaust flowage already in place.

Ed
 
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#7 ·
I am doing a job next week where the lady has mold. Want to know what it's from? Having ridge-vent and gable vents. When I went in the attic, there were actual piles of snow under the gable vents.

I know Dennis doesn't think that you can short circuit ventilation but my own discoveries and research have proved me otherwise.
 
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#8 ·
When a Powered Attic Ventilator begins it's cycle, a great volume of CFM will look to be expelled.

Since the Attic Fan location is typically also located near the upper regions of the roof, nearest to the ridge, the Ridge Vents would then be induced into operating as a source of air intake to supply the exhaust fan, following the logic that the air flow will come from not only the nearest source, but also from the one which offers the path of least resistance.

It is not advised.

Ed
 
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#9 ·
Ed,

I honestly can not say, that any of the Air Vent videos that I have seen or own, (And Paul Scelsi of Air Vent has graciously allowed me to be privy to videos that are not publicly available), has not shown any with Gable Vents added to the mixture with the smoke tests.

Personally, just in my opinion, I do tend to put more weight in the theory of "Short-Circuiting" the attic ventilation flowage from lower soffit area vents to the roof top exhaust vents when gable vents are introduced to the scenario, but I have not seen conclusive evidence to either support or denounce that theory. Although I have read continual observations from respected Home Inspectors and Contractors that do support the "Short-Circuiting" aspect, those can only be taken at face value without due consideration of knowing all of the other factors that may have been in play at the time.

So, I guess I could have just taken the easier way of making my point by stating, "It Depends".
Click to expand...
The ventilation manufacturers and most widely accepted ventilation studies and theories show that the gable vent air flowage would interfere, also know as Short-Circuit the current soffit to ridge ventilation flowage.
Click to expand...
I take it you have found some new studies??? Care to share?
 
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#12 ·
BamBamm,

I recently finished this roof. This winter snow blew into this dormer vent that was installed by the carpenters. Enough snow got in to cause a leak in the ceiling.

Do I blame the ridge vent for causing a short circuit?
No, because there is no ridge vent.

I blame the poorly designed dormer vent.

You might want to look into other causes for your customers mold such as insulation and air sealing issues.

Image
 
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#14 ·
Hi Tom,

That was probably mine. Was it of low quality and budget and looked like it was filmed in a basement? :whistling

I don't think there are any other sites or sources of information relating to the issue. That's why I made the video. The short circuit concept didn't make sense to me.
 
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#17 ·
if the customer currently has gable vents, i would close them up if a ridge vent is installed. of course you would want to make sure there is enough intake from the soffits. installing ridge vent and then leaving the gable vents will interrupt the natural convection from the ridge. thats how it was explained to me and it does make sense. picture a vacuum and then putting a hole in the hose.
as far as an attic fan,i am not entirely sure about that. need to delve into it more.
 
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#18 ·
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#20 ·
Interesting videos Dennis,
Makes me wonder too about closing
gable end vents when ridge vents are installed.
I always wanted to do a similar experiment when
this argument first came up but figured that actual,
real life conditions would be hard to duplicate and
control.

One condition would be actual varying outside humidity
and temperature conditions in comparison to interior
attic humidity and the varying densities of heated
air as it left the conditioned areas of the house.

Since any moisture laden warmer air leaving
the conditioned area of the house may be heavier
than outside air,I can't help but think that there
may still be a possibility to have a short circuit
by leaving in the gable end vents.
I like the demo but feel it has to be taken a couple
steps further to really prove this point.
Burning incense is just dry heated smoke which
I don't think can be a substitute for actual attic
conditions.

Just saying............
 
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#22 ·
I have always removed the gable vents when I install new ridge vents.

Having said that, I have found nothing in the lit. anywhere that says it is imperative to do so.

I have never liked powered vents, exception being is if I lived in the south. My opinion is they are highly unnecessary for most applications.
 
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#24 ·
[QUOTEI always wanted to do a similar experiment when
this argument first came up but figured that actual,
real life conditions would be hard to duplicate and
control.][/QUOTE]

I agree. We can design the perfect house on paper, but it may not look anything like what gets built. One size does not fit all.
The videos are not perfect scientific studies, but I think they illustrate the basic concept. I will leave it to better minds to figure out the humidity problem.

i see many opinions. however, IF THE GABLE VENTS ARE REMOVED after putting in ridge vents, can that cause any harm ? or is removing the vents just a waste of time at that point?
what about removing the vents but keeping the attic fan ?
Click to expand...
That depends. If you live near me, your ridge vents could be covered in snow for weeks at a time and the additional gable vents are a plus. If you have a mcmansion with hips and short ridges,or live in the south, the attic fan would be a plus.
 
#25 ·
The gable vent is usually closed off when there is soffit and ridge vent system. If you have a ridge vent, it might draw the air from the gable and not from the soffit, and being gable vent considered to be the worst attic ventilation source, you could have some serious problems.

Take a wood burning fireplace for instance. When you burn the fireplace, it takes all the heat from the room out. If you crank a near by window, it will draw the cold air in, leaving the hot air in the room.:thumbsup:
 
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#27 ·
Take a wood burning fireplace for instance. When you burn the fireplace, it takes all the heat from the room out. If you crank a near by window, it will draw the cold air in, leaving the hot air in the room
Click to expand...
Hi Greg,

Not a very good analogy, but;

The way you are thinking about it, that fireplace is heat gain in the attic with a small roof vent, and no other vents.
A very warm room(attic) until you open the window(intake).

To make that analogy more meaningful.
Cut short vents all along the exterior wall at the baseboard to simulate soffit vents. Enough to compensate for the draft of the fireplace. Now open the window.
 
#28 ·
It is very simple... the outside air enters your attic space at the bottom edge of your roof and is being exhausted at the highest point of your attic. This makes ventilating systems use wind and thermal convection to always move and exchange air in the attic with outside air. When you have a windy day, wind blowing across the top of ridge vent and creates a vacuum which pulls the air out of the attic. On the days when there is no wind, hot air builds up in the attic, and leaves through the ridge or roof vent which always located at the top of roof and that is why Ridge and Soffit vent system is the most efficient ventilating system.
 
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#29 ·
that is why Ridge and Soffit vent system is the most efficient ventilating system.
Click to expand...
I agree, unless ,
a. your ridge vent is plugged by debris or wind driven snow ( I have pictures)
b. your ridge vent is covered in snow for long periods( I have pictures)
c. your roof is made up of hips and valleys with no room for ridge vents

I am not against using ridge vents. Just trying to clear up the "short circuit " myth.
 
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#30 ·
dennis said:
I am not against using ridge vents. Just trying to clear up the "short circuit " myth.
Click to expand...

From all the reading I've been doing,
it seems more fact ,than myth.
Your demonstration just shows what
dry smoke will do.The whole purpose
of ventilation is to remove any moisture.

One day after finishing a reroof where the HO
insisted on keeping his gable end vents,he
called to say something wasn't right.
When I arrived I noticed a mist in the
attic space.It was because the ridge vent was now
drawing outside fog in through the gable vents.
We closed the vents off,he never had a problem again.

Here's something I found on damage done by
short circuiting.Although part of the problem was
the lack of adequate soffit vents,the gable end
vents greatly added to the damage:
http://www.ronhungarter.com/ventilation_repairs.html
 
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