Attic Ventilation

Attic Ventilation

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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  1. 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

  2. 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.

  3. 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

  4. 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 8) 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,

  5. 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


  7. I have a 3 year old house in fla,suppoidly has a ridge 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

  8. 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

  9. 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

  10. 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.

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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 ?

  16. 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?


  18. My bedroom has an odor that seems to be coming from the ceiling and the attic has the same odor. The smell is not defined at night but is extremely strong beginning between 10:30am-11:00. I’ve had my attic checked for leaks and mold but nothing was found and the odor was obvious. Any suggestions on what could be the problem?

  19. Hi,
    I have 2 ridge vents, several soffit vents, and a large attic that could be a second floor. The attic hatch is in the hallway and is blocked with a piece of heavy board. Since heat rises, I was wondering if I replaced the board with a screen in summer, would my house be cooler? If it matters, my house is about 1,000 sq. feet, and the hatch screen would be about 3.5 feet x 4 feet. Thank you, Jean

  20. I asked above about leaving the attic hatch open with just a screen there. I meant without my AC being on and with all my windows open.

  21. I live in Kailua, HI, and Our home was built in 1955. the attic builds up tremendous amounts of heat, especially in the summer. There are soffett vents around the roof overhang, but not many.. and there are no ridge vents. the attic smells pretty musty . I want to add ridge vents, and additional soffet vents. Are there preferred “ridge vent” options for warmer climates?
    thanks! Jim

  22. I have just insulated my 19 x 11 foot shed that has an aluminum roof. It also has soffit vents but other than that no other venting. I am planning to install Gable vents at either end. Can you comment on if that is enough ventilation. There is an insulated ceiling as well in the shed. I want to avoid having to put any type of venting into the aluminnum roof such as a ridge vent or whirl vent.
    Thanks for your time

  23. Hi Ben, Danny,

    The house I bought had a 3 season porch added on years after it was built. I’ve since enclosed it to make it into a playroom. I need to add a ridge vent and some soffit ventilation, throw up some roof baffles from the soffit to the ridge vent and insulate. However, there is a portion of the addition that is built over the exiting roof. I plan to block that off.

    So my question is, how do I ventilate that portion of the roof?

    I’ll extend the ridge vent on the roof addition to within a foot of the existing roof. But somehow I don’t think that’ll be enough ventilation. Perhaps some sort of vent on either side of the roof?


  24. We have mold in our attic now, we have a lot of moisture up there we are not sure why one thing is our bathroom vent is being vented up to the attic we know now that it needs to go outside this is a new home so we weren’t sure at first…. We have ridge vents on top of roof and we also have the sofit holes for vents i’m not sure if it’s just the bathroom vent issue that has caused all our mold or if it’s something else. It’s very hot up there and a lot of mostuire and now mold.

  25. Hi, I alive in Colorado. Temps can go from 104 to below zero in a given year. My house has a basement and main floor. The man n floor is 2300 sq ft. I have 2 gable vents and no soffit vents. I used to have 2 of those round vents that moved when the wind let them. My kids would cover them with the cover I purchased. Due to hail damage, my roof was replaced 2 years ago and they insisted I did not need the round vents. Instead they put 3 vents that are low to the roof. It sounds like I need soffit vents, how many? Should I get a whole house fan? What all do I need? Thank you in advance, Peggy

  26. My roofing contractor is suggesting a Positive Pressure Attic Ventilation system to drive excessive heat from my attic. I have ridge vents, soffit vents and 6 convection vents on the house. The contractor states that if I put a powered fan that is connected to a thermostat low on my roof (close to the edge of the roof on the south facing side) it will draw outside air into the attic creating Positive Pressure Ventilation and force the hot air up and out of the attic. In theory this makes sense. However I am concerned that there may be hidden issues with doing this. Any thoughts are most welcome.

    • Hi, Marc,
      Here’s “Today’s Homeowner” host Danny Lipford’s answer to your question:
      “A thermostatically controlled attic exhaust fan can move a lot of hot, moist air out of your attic. However, you have to consider that it is using electricity to do this. And will not work properly if you still have ridge venting in place.”
      Thanks for your question.

  27. I have a 2000 sf single story home in Bedford Texas w/ 33 soffit vents around the perimeter overhanging roof line. It’s very hot in the attic and on closer inspection , I find most of the soffits are Blocked by kraft backed insulation resulting in very little ventilation. I’ve tried to move and open up the areas but at 77 yrs old, I’m not having any luck. Found mold in A/C plenum( now replaced), but really need much better ventilation. I don’t mind paying a fair price to get my soffits opened but, finding someone to help is a big problem. I’m in 76021 area code. Can you help me please? Thanks very much for your time. David C

    • Hi, David, features home improvement advice from the nationally syndicated TV show “Today’s Homeowner” and its experts.
      We don’t offer information on individual home builders and suppliers, but we encourage checking your local phone listings for this information.
      Good luck, and thanks for your question!

  28. Thanks for helping me learn more about attic ventilation. My uncle gave me one of his old properties and it seems like this house is … shall we say … somewhat skeletal since it lost most of the functions that make it a house. The idea of installing a type of ventilation that can increase the lifespan of one’s roof and lowers our energy bill is great! I should discuss this first with my mom before jumping the gun.


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