Do gable vents work?

Originally Posted By: hvanderbeek
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Originally Posted By: gbeaumont
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Hi Hank,

good to see you around. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

Gable vents will work if thy are large enough to give adequate trough-flow of air, but ridge and soffit vents are much more efficient.

The real issue here is that the bathroom exhaust fans should be ducted to the exterior. Didn't I teach you ANYTHING ??



Gerry Beaumont
NACHI Education Committee
e-mail :
NACHI phone 484-429-5466

Inspection Depot Education

"Education is a journey, not a destination"

Originally Posted By: cmccann
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My experience with gable vents is they only work when the wind is blowing and blowing directly into a vent.


Originally Posted By: dedwards
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My part of the country they work fine, especially if they are equipped with a gable vent mechanical fan. It pulls air through the attic and dispels it out the other end. I had a ridge vent / soffit vent system on my own home until I went through HVAC school and saw the difference mechanical systems makes. The average temperature in the summer in an attic here in NW Florida is about 135 and up. I installed a set of gable vents, a mechanical fan with an inline thermostat and now the average temp is about 100 degrees. I set the inline thermostat for 95 degrees so it runs a lot. Mine is run off 240 volts and pulls only 1 amp so the cost benefit trade off is great. This also pulls the moisture out. I always recommend to folks interested to put the fan over the end of the house opposite the bedrooms to lessen the chance of noise. Mine is directly above the laundry room but you can still only barely hear it running. I have checked the air temperature coming out of the “exhaust” gable and it is usually 20-30 degrees warmer than the ambient air. For my money it is worth every penny. On ridge vent: I wish I had a dollar for every home I have inspected with a ridge vent where the roof sheathing and or the felt paper is blocking the ridge gap. Looks good but doing nothing. Same for soffit vents, unless baffles are installed I find over half are blocked off by the insulation. The heat build up in the attics is what shortens the life of the shingles.

Originally Posted By: bgentry
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I agree. If you have gable vents only, you need a fan. If the wind is blowing at perp. to the ridge, instead of parallel, the unassisted vents will defeat their own purpose. I still feel that soffit and ridge vents are the best for colder climates, though, because the air flow helps prevent ice damming and controls moisture build up on the underside of the roof decking.

By the way, mechanical vents in northern climates should also have a humidistat as well as a thermostat. The thermostat will never turn the fan on during the winter, but the humidistat will.

Originally Posted By: rmoore
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Roof or attic ventilation seems to almost an art rather than a science, and what is effective in one area, or home may actually cause problems in others. I?ve seen a whole load of ?articles? that imply that you can?t have too much ventilation. The following couple would suggest that preventing moisture entry by sealing the ceiling plane is more important. The second also points out that sometimes less is more when it comes to ventilation types.

I?m sure gable vents work well in some situations, but I should point out that I found the above links while researching a bad case of black mold, moist sheathing and warped hardboard gable end siding in a triplex attic where gable end vents were the main, and obviously inadequate, ventilation.

You probably can?t beat eave or soffit vents and a continuous ridge vent for a passive system (when possible).

Richard Moore
Rest Assured Inspection Services
Seattle, WA

Originally Posted By: kwilliams
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I don?t think this as a problem, but would like some feedback

on it. I have had this Ranch house for about a year. It has soffit vents

And 4 roof vents on the west side of the house. There are no signs

of any problems in the attic. The prevailing winds come from the west,

As it is on a hill it is blowing somewhat most of the time. When I

was replacing the soffit vents that where somewhat panted shut last summer

Hot air was blasting out of them, so the venting is reversed so to speak.

Any feedback would be appreciated.

Member - MAB

Originally Posted By: dedwards
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Excellent articles / links. Plan to re-read through them at first chance. I agree. It depends a great deal on where you are living and the time of the year. Also depends on the type of construction. There are a lot of lessons being relearned recently. What conventional wisdom used to think has caused some of the problems in the building industry today. One of the reasons I subscribe to Journal of Light Construction magazine. It is always got something timely written in it about the problems faced by the contractors. We have hundreds of very old well built homes in and around Pensacola because this used to be a lumber town at the turn of the century. The previous one not the last one. Those houses don’t have many of the problems with moisture, mold and rot that newer ones do. Mainly because they weren’t built so airtight.

This is one reason I contend that one test for Home inspectors isn’t good. We all live in very different environments and see where some things we take for granted in the South is very important to those who live in the North. Extreme weather conditions with the exception of a few hurricanes is not too common here. The only time you hear the words “ice” and “dam” is used in the same sentence here is when someone says. “Damn, my ice melted in my drink.” The reason I set the in line thermostat on 95 is to keep the attic hot enough to cook off any moisture. It works very very well. That along with the fan keeps it just hot enough but not too hot. I appreciate the links. Thanks

Originally Posted By: dedwards
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Sounds like the prevaling winds were strong enough to force the hot air back out the soffit vents once you opened them up. Check to see if you upper vents are not blocked and you have clear access up the roof to them. I find a lot of times the baffles are gone or covered up with insulation. Most of the home I inspect the number of soffits vents is woefully inadequate to move any real air out of the attic. If I can find the website for the formula to determine adequate ventilation I will post it.

Originally Posted By: kwilliams
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Thanks Doug, Nothing is blocked and in fact

it’s the wind that’s doing it, as I said, I checked

and there are no problems up in attic. I have just not

come across this before. The back of the house is

the west side, I am sure when they built the house in

1964 they put the roof vents there so you couldn’t

see them from the street. Just wondering if anybody

else has come across this. I do not think it’s a problem

as this is in the northeast with lots of snow and stuff.

and as I said there are no problems in the attic.

Member - MAB