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Attic Ventilation
By: Danny Lipford 
Attic ventilation is crucial to the longevity of your roof and can help to lower your energy bill as well. Vents can be located in gables, under eaves, along the ridge of the house, or cut into the roof itself.
Hot air in your attic may not seem like such a bad thing in the winter, but it contains moisture that can condense and cause long term problems. In summer, heat in the attic not only makes your air conditioner work harder, but it also cooks roof shingles from the underside and reduces their life.
Continuous ridge vents have become popular in recent years for good reason. Since hot air rises, it’s important to locate the vent as close to the peak of the roof as possible, and nothing is higher than the ridge. While they come in a number of different types, one system uses a fiber mat laid along the ridge with shingle tabs mounted over it. A narrow slot cut in the ridge allows hot air in the attic to escape while keeping insects and rain out.
In order for ridge vents to be effective, you need a supply of fresh air coming in from the soffit under the roof’s overhang. Soffit vents are available in a number of styles including round and rectangular metal vents, integrated vinyl soffit vent panels, or continuous trench vents. By combining a balance of both soffit and ridge vents, you can create a constant flow of cool, dry air through your attic in both winter and summer.
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18 Comments on “Attic Ventilation”
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October 27th, 2007 at 12:24 pm
Mechanical ventilation (fans).These are seldom checked most of them have a thermostat-which tends to fail over the years.These should be on the check list when your AC check up is due.some fans have dampers which open with the fan.If the fan tstat is broken then 0 air is moving and can buckle the roof around the fan opening,because of the metal,which expands and contracts at a faster rate than the wood.When you get the xmas tree down check the fan-its worth the 5 min.
John Cannamela
Go green with Infrared
http://www.infraredsurvey.com
November 14th, 2007 at 2:49 am
I think the best way is by install ridge vents,the full lenght of the house , LIVING QUARTERS. This way the heat in between trusses or rafters can escape throught the ridge vents.
November 14th, 2007 at 3:00 am
To get hot air from your attic is to install a ridge vent an check if there are thru vents an soffit vents .
November 25th, 2007 at 6:17 pm
we have round vents under our soffit they need to be replaced where can we buy them in fort myers florida or on line .thanks barbara
January 2nd, 2008 at 12:48 pm
Hi I have gable end vents and no soffit vents i intend to do a new roof soon with a ridge vent do i need soffit vents or what other procees should i use. Bob
February 5th, 2008 at 11:10 am
Within the past two years we had new roofing paper and shingles installed on our 9/12 pitch roof. This was not an overlay. At the same time we had the turtle vents removed and continous roof vents installed. We left the soffit vents and the gable end vent on the north east side intact (only one gable end because of chimney). Shortly after the shingles were installed we climbed through the access hole to check the inside of the roof. We found a great deal of mold, primarily over the bathroom located on the south west side of the house. However, we feel certain the mold was there before new shingles were installed.
We treated the mold with a solution of bleach and water which killed the mold. We checked a few months later and the mold had not reappeared.
Later, I was told that the gable end vent should be closed off as it did not work well with ridge vent. I did close the gable end with foil and duct tape. The soffits are vinyl and have very small vent holes that are not visible under beadwork that runs perpindicular to the house.
We have a r-19 factor attic insulation (at least) on 2nd floor celinig.
The bathroom fan vents empty into the soffit.
Now several months (7 or
after we last checked we find the mold is back.
We have questions.
1. Should I uncover the gable end vent even though we have ridge vent in place?
2. Do you feel the bleach and water solution sprayed on the mold with a garden sprayer will defeat the mold? Or are we going to end up replacing the sheeting and shingles?
3. Will an attic vent fan help?
4. Is attic mold a common problem in newer homes?
Thank you,
Bill
February 27th, 2008 at 5:31 pm
Check for leaks around your chimney if it is at that area. I think the issue may be your bathroom exhaust fan (assuming you have one). Sometimes these are vented directly into the attic. It should really have an insulated duct connected to it that goes to the outside wall through a weather-proof cover like on your clothes dryer vent. Keep in mind sloping the duct to the outside wall too because you are bound to get a little condensation in it. You want to drain outside, not settle in low spots or drain back into the bathroom. Keeping gable vent closed makes sense to me. Make sure your soffit vents aren’t plugged up with dust/dirt or bugs and you should be good to go. Good luck, Karl
March 9th, 2008 at 1:45 am
I AM INSTALLING INSULATION AGAINST THE ROOF DECKING IN MY ATTIC. I PUT STYROFOAM BAFFLES IN FIRST TO ALLOW AIR FLOW TO THE RIDGE VENT. SHOULD I BE ABLE TO FEEL THE FLOW COMING UP FROM THE EAVES? IF NOT PERHAPS I NEED BETTER SOFFIT VENTS. ALSO, HOW FAR UP FROM THE VERY BOTTOM OF THE ROOF SHOULD I PLACE THE STYROFOM BAFFLES?
November 15th, 2008 at 7:39 am
I have a 3 year old house in fla,suppoidly has a ridge vent.it seems they definitly cut the ridge and put paper thin mesh and then the shingles on top water tight so the ridge vent is sticking up1/8 of inch,how could this possibly vent or is this just a contractors cut and you are responsible to install the actual vent.its impossible to get any air out when the shingles are nailed down tight as normal.the cobra vent is an inch thick looks to be ok
November 17th, 2008 at 7:53 pm
I had paperlike insulation blown into my attic recently. There is no roof vent and I was told that 2 soffits were left open but there are no baffles and I’m not sure they protected the two soffits they say they left open. There is a very small vent in the top corner at each end. A contractor looked at the other soffits from outside and said they were of no use because they don’t go directly into the atic. The pulldown for attic access has no cover and I was told by the contractor there is not enough ventilation and that I will get mold and roof and beam damage. Please respond with your advise as soon as possible so that I can get back with the contractor that installed it and take care of the problem. It gets pretty cold here in New York and although I feel insulation is necessary, I would rather not have it done incorrectly and create a problem later on. I’m an elderly widow and need your expert opinion and advise. Thank you for your quick response. Mrs. Pringle
December 6th, 2008 at 12:55 pm
Thank you Dan for reading my e-mail concerning the insulation in my attic with not enough ventilation and my concern of what the results will be like mold or anything else. I am also concerned also for any health problems that can occur. I have been waiting for your response to my request but have not seen it yet. It’s so very important to me. I’ll be looking for it and thank you again. You are a help to so many people like me. Mrs. Marion Pringle
Ben Erickson Says:December 9th, 2008 at 11:53 am
Hi Marion,
Inadequate attic ventilation in a cold climate can lead to condensation and mold in the attic. The rule of thumb on attic venting is approximately 1 sq. ft. of vent space for every 150 sq. ft. of attic area. So if your attic is 1,500 sq. ft., you would need 10 sq. ft. of vent area. Ideally, half the vents should be located in the soffit at the bottom of the roof and half in gable or ridge vents near the top.
December 26th, 2008 at 1:47 pm
Dear Ben,
Thank you for answering my request for information of my concern for what would happen without proper ventilation and exhaust in my attic and the insulation. I was told by a contractor(not the one that installed it)that I would get mold and you confirmed it.
Taking your time to help me is so much appreciated. Again, thank you.
Marion Pringle
December 26th, 2008 at 2:10 pm
Hi Ben, I just finished reading some of the other problems people are having and one of them was the bathroom exhaust.
My bathroom exhaust is directly into the attic which is covered with insulation. Now I will have another problem which I don’t know why the insulation installer did not alert me to this and the other situations before installing it. If the installer told me he left two soffits open, then shouln’t I see a baffle in that area?
Your help or anyone else who reads this can jump in with their reply.
Thanks, Marion Pringle
January 24th, 2009 at 11:01 am
Hi Ben,
I haven’t received your response to my e-mail 12/26/08.
What is your recommendation as to what I should tell the installer and is he accountable for installing the insulation before explaining what happens if there isn’t the proper amount of ventilation and exhaust and not installing it before the corrections were made.
Thank you Marion Pringle
Ben Erickson Says:January 26th, 2009 at 9:50 am
Hi Marion,
The insulation installer should check to be sure there is proper ventilation in the attic and take precautions to see that any soffit vents are not blocked by installing baffles, which should be visible above the blown insulation. You should also run a vent pipe from your bathroom fan to the outside to keep the warm, moist air from condensing in your attic.
February 5th, 2010 at 7:04 am
I have a bonus room (400sf ) with that had gable vent and 4 turtle vents on the back side of the house. During recent re-roof , the roofer did away with the turtle vents, left the gable vent and installed ridge vent (cutting the decking only of the steep pitch side ). It appears that there are only 2 soffit vents for this area and any addition make up air would have to come from the main part of the attic which has 8 soffit . Any opinion on whether I need to install turtle vents for this area ?
January 28th, 2012 at 10:24 pm
my house is 1300 sq. ft.I have 3 gable end vents with a attic fan on thermostat at 105 degree and 3 daomer vents on the roof. i have no vents into the attic such as soffit vents along the sides of the house. Do I need any and how many?