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  1. #1
    Larry Hood's Avatar
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    Default Attic Ventilation

    In an older home I was told that the gable vents should be sealed.The attic has R-30 insulation,a ridge vent and soffits that are vented.Came you advise me if this is a good or bad direction.

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  2. #2
    James Duffin's Avatar
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    Default Re: Attic Ventilation

    My opinion is they should not be sealed. The closer you can keep the attic temperature to the outside temperature the better off you are. I'm sure other folks will not agree but that is my thinking on the matter.


  3. #3
    Ted Menelly's Avatar
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    Default Re: Attic Ventilation

    Quote Originally Posted by Larry Hood View Post
    In an older home I was told that the gable vents should be sealed.The attic has R-30 insulation,a ridge vent and soffits that are vented.Came you advise me if this is a good or bad direction.
    You know, honestly it is to difficult to say with out the home at hand and the pitch of the roof and how much soffit vents and such. In all I would have to agree with James.

    When I only find gable vents at the far ends of the home and there is that hot or cold and damp stagnant air day the air just sits in that attic and may slowly vent all the way to the ends of the home I advise my client to evenly space out a couple turbine type vents or add ridge vent on most of the ridge. If the home is in a high wind area and windy most of the year then the gable vents may take care of the ventilation.

    Again, the home, the area, the roof pitch, north, south, east, west layout....much to consider but just adding the ridge vent is a safe bet and not close the gables


  4. #4
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    Default Re: Attic Ventilation

    Seal gable vents and use properly spaced and balanced soffit and ridge vents... most of the time. If the roof is simple, then keep it simple, cool air in the bottom and hot air out the top. A gable end vent can act as an inlet slightly pressurizing the attic defeating the air flow strategy of drawing cool air in through the soffit and exhausting it out the ridge.
    A more complex roof structure with multiple gables might yield a different answer.

    Last edited by Jim Luttrall; 10-07-2010 at 07:53 PM.
    Jim Luttrall
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  5. #5
    chris mcintyre's Avatar
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    Default Re: Attic Ventilation

    I agree with Jim.

    Here is (IMO) a good document on attic ventilation.

    Attached Files Attached Files

  6. #6
    James Duffin's Avatar
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    Default Re: Attic Ventilation

    Good info in the pdf. But I'll stick to my idea that the more openings into the attic the better off you are. The pdf said numerous times (I think) that the goal is to keep the attic as cool as you can in the summer and below freezing in the winter. You can do it using their products or by any other method available. What you are after is lots of holes into the attic that will not let in rain or snow.


  7. #7
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    Default Re: Attic Ventilation

    Logically the attic needs a convection current to vent when the wind is not blowing to assist it. If there are gable, eave and ridge vents, the air will take the path of least resistance and enter through gable vents and exit the ridge vent leaving the lower reaches hot or cold. However, Jim's logic is also sound. The more vents the better. For me the jury is still out on the matter.

    I have come to realize that turbine vents are not a good thing though and no longer recommend them. I have seen several attics with kiddie swimming pools placed under the turbines because if the rain is driven hard enough or if there is no wind and the turbine does not spin and it's raining, rain water comes in through the turbine openings and saturates the insulation causing it to settle and become of less value or totally ineffective. If a catch basin like a pool is placed to catch the water, insulation is packed down and becomes less effective as well.

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  8. #8
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    Default Re: Attic Ventilation

    I agree the more venting you have the better to cool and reduce moisture. However if you have " properly" installed ridge vents which are open evenly and to the max. on both sides of the ridge board along w/ soffit vents and rafter baffles you shouldn't need gable vents. As JL and JD said it can only confuse air flow when you have ridge,soffit and gable vents.


  9. #9
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    Default Re: Attic Ventilation

    When an attic is balanced correctly (right number of openings at the soffit and ridge) You can actually feel the pressure sweeping air to the ridge. In an older house you might not really have enough soffit vents that gives enough air flow. I do agree the gable vents should be covered, however, it does depend on how well the ventilation of the soffit and ridge is working.

    Randy Gordon, construction
    Michigan Building Inspector/Plan Reviewer

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    Default Re: Attic Ventilation

    There are numerous variable involving air flow and the size of the vents. I suggest trying both and seeing what happens, and then let us know. Is it your house?

    Jim Robinson
    New Mexico, USA

  11. #11
    David Valley's Avatar
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    Default Re: Attic Ventilation

    When ridge and soffit vents are properly cut-in...then gable end vents can/should be sealed.

    Massachusetts Home Inspection: Attic Ventilation


  12. #12
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    Default Re: Attic Ventilation

    Unless there is very little ridge vent, having both ridge vents and gable vents will confuse air flow and I would say the gable vents should be sealed. Also make sure there is enough soffit ventilation, to balance ridge vents with typically 18 sqin/'nfa you would need 9sqin/' nfa continuous soffit venting.


  13. #13
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    Default Re: Attic Ventilation

    Florida is hot and very humid most of the year. It is important to get that heat and moisture out of the attic. To that end, I would never tell someone to remove attic ventilation. Keep in mind that hot air rises. As it rises to the vents, it is going to be displaced by cooler air from the soffit vents. That is basic physics.

    Since all the vents are static air vents, one vent is not going to confuse the other. The air is going to move through the vent whether it is a ridge vent or a gable vent. Yes you will have air entering through one or the other vent under certain circumstances, such as wind blowing at the vent, but that is going to happen even if you have one small vent at the top and soffit vents. Wind blowing against the gable is going to blow into that gable but the other vents will allow it to get back out. But keep in mind that that will happen with the ridge vents or the soffit vents if the wind is blowing in the correct direction.

    Having the combination of both just gives the hot air more opportunities to get out of the attic. I will bet that going into that attic was much more comfortable than going into the same attic if the gable vents were covered. I have yet to find an attic that was comfortable with ridge vents alone.

    I would be more likely to recommend someone add ventilation than to ever recommend removing existing ventilation.

    Robert Sole
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  14. #14
    Tom Tamlyn's Avatar
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    Default Re: Attic Ventilation

    Personally I would agree the more ventilation the better. But I attended an Air Vent seminar and per their website this is their comment:
    Q: Do I have to close off my gable vents when I use a ridge vent?
    A: Yes, the gable vents should be closed off whenever a ridge vent is installed because vents installed at the roof's edge or in the overhang should suppy the intake air needed by the ridge vents. Air should flow in through the intake vents evenly along the roofline and exhaust out the peak. Any vents in place between the ridge vents and the intake vents may interrupt or short-circuit that flow of air along the roofline. The gable vents will end up becoming intake for the ridge vent--an undesirable situation that could lead to weather infiltration through the gable vents and also could prevent the attic from being properly ventilated. The same is true of mixing wind turbines or roof louvers with ridge vents.


  15. #15
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    Default Re: Attic Ventilation

    Quote Originally Posted by Robert Sole View Post
    Florida is hot and very humid most of the year. It is important to get that heat and moisture out of the attic. To that end, I would never tell someone to remove attic ventilation. Keep in mind that hot air rises. As it rises to the vents, it is going to be displaced by cooler air from the soffit vents. That is basic physics.

    Since all the vents are static air vents, one vent is not going to confuse the other. The air is going to move through the vent whether it is a ridge vent or a gable vent. Yes you will have air entering through one or the other vent under certain circumstances, such as wind blowing at the vent, but that is going to happen even if you have one small vent at the top and soffit vents. Wind blowing against the gable is going to blow into that gable but the other vents will allow it to get back out. But keep in mind that that will happen with the ridge vents or the soffit vents if the wind is blowing in the correct direction.

    Having the combination of both just gives the hot air more opportunities to get out of the attic. I will bet that going into that attic was much more comfortable than going into the same attic if the gable vents were covered. I have yet to find an attic that was comfortable with ridge vents alone.

    I would be more likely to recommend someone add ventilation than to ever recommend removing existing ventilation.
    I agree....the more holes into an attic the better. I have noticed a pattern that the documentation that says to use soffit and ridge vents only are the same folks who make the soffit and ridge vent products. I wonder why that is?


  16. #16
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    Default Re: Attic Ventilation

    Quote Originally Posted by James Duffin View Post
    I agree....the more holes into an attic the better. I have noticed a pattern that the documentation that says to use soffit and ridge vents only are the same folks who make the soffit and ridge vent products. I wonder why that is?
    Maybe because they actually understand how and why their product works instead of just "more holes is better"

    Jim Luttrall
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    Default Re: Attic Ventilation

    Confuse the air flow? Short circuit the air flow? You are not trying to create a vacuum cleaner to suck the cob webs off of the bushes. Hot air rises, it will find its way to the ridge vents and the gable vents. I don't think you can have too much fun or ventilation.

    The beatings will continue until morale has improved. mgt.

  18. #18
    James Duffin's Avatar
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    Default Re: Attic Ventilation

    Quote Originally Posted by Jim Luttrall View Post
    Maybe because they actually understand how and why their product works instead of just "more holes is better"
    Or it could be they want to sell more stuff!


  19. #19
    James Duffin's Avatar
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    Default Re: Attic Ventilation

    Here is an informative article from somebody who is not trying to sell you anything.


    Roof and Attic Ventilation | Attic Ventilation | Roofing

    Roof Ventilation | The Short Circuit Myth | Attic Ventilation | Roofing


  20. #20
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    Default Re: Attic Ventilation

    JD, I will give you that the document I posted is from a company that is selling something, but I am finding it hard to change my position based on a video using a cardboard house and burning incense sticks to dispute an industry standard.

    ........The house; a simple gable roof constructed of corrugated cardboard.
    ........Burning incense sticks placed on a tray and inserted into the attic simulate hot attic air.

    I will say based on the video that if a house catches on fire that smoke will exit through the gable vents as well as the ridge vent.


  21. #21
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    Default Re: Attic Ventilation

    Have you ever been in an attic with loose fill insulation that has been moved around by wind blowing into the attic through the gable vents? Air does without a doubt INTAKE through the gable vents. The key is you want uniform air movement throughout the entire attic. The ridge and soffit vents are designed by the manufacturer to function as a system, not a hodge podge of parts cobbled together because the roofer thought it was better to have more holes. Sorry guys, I'm just not buying the argument. Balance ventilation means having the same amount of high vents as low vents. Throwing a few more holes at the top of the gables might work but it might not. Stick to the manufacturer's instructions.
    Do you really think that the manufacturers would recommend closing the other vents if leaving them open would make their product work better?

    Then there is the other situation with blowing snow... guess which vent will let in the most snow.

    Jim Luttrall
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  22. #22
    James Duffin's Avatar
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    Default Re: Attic Ventilation

    Quote Originally Posted by chris mcintyre View Post
    JD, I will give you that the document I posted is from a company that is selling something, but I am finding it hard to change my position based on a video using a cardboard house and burning incense sticks to dispute an industry standard.




    I will say based on the video that if a house catches on fire that smoke will exit through the gable vents as well as the ridge vent.
    Not trying to change your mind.....just stating what I believe to be the obvious. If I am in a hot room with large windows on both sides of the room and vent in the floor and a roof vent.....I believe I would open the windows to get the heat out of the room the quickest way. It is true that the floor vent and roof vent will be useless with the windows open but it really does not matter at this point. Shut the windows and the floor and roof vent will start working again but not as well as the open windows.

    I have on numerous occasions recommended increasing attic ventilation but have never recommended that it be decreased. That does not even sound right.....there is too much air entering and leaving the attic.


  23. #23
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    Default Re: Attic Ventilation

    As the others have said: it depends, sometimes, yes, maybe, and probably.

    It depends on if there is appropriate ridge and soffit ventilation, if so, seal the gable vents up.

    Sometimes there may be things which would make adding gable vents to ridge and soffit vents practical, but not usually and not under most circumstances.

    Yes, seal the gable vents up as it short-circuits the soffit-ridge air flow ... usually anyway.

    Maybe as there may not be very much soffit ventilation area, but then, instead of leaving the gable vents you really should provide more soffit ventilation, then seal the gable vents up.

    Probably all of the above are correct and you should seal the gable vents up.

    I.e., seal the gable vents up, but consider all the things you observed about that house that were not relayed to us before doing so - generally gable vents are not a good idea with soffit and ridge ventilation.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Attic Ventilation

    Quote Originally Posted by Jim Luttrall View Post
    Have you ever been in an attic with loose fill insulation that has been moved around by wind blowing into the attic through the gable vents? Air does without a doubt INTAKE through the gable vents. The key is you want uniform air movement throughout the entire attic. The ridge and soffit vents are designed by the manufacturer to function as a system, not a hodge podge of parts cobbled together because the roofer thought it was better to have more holes. Sorry guys, I'm just not buying the argument. Balance ventilation means having the same amount of high vents as low vents. Throwing a few more holes at the top of the gables might work but it might not. Stick to the manufacturer's instructions.
    Do you really think that the manufacturers would recommend closing the other vents if leaving them open would make their product work better?

    Then there is the other situation with blowing snow... guess which vent will let in the most snow.
    Used to live in a house in NJ that had gable vents. Had to seal them because of blowing snow. Based upon some previous comments about turbine ventilators and powered ventilator systems---they may also permit blowing snow as well as rain to enter the home. Does anyone have experience with the metal or plastic ridge vents allowing fine snow to enter the home?


  25. #25
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    Default Re: Attic Ventilation

    Likely yes, the openings should be reinforced and closed, especially if you're upgrading to meet your wind resistance retrofit qualifications on those gable end walls.


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    Default Re: Attic Ventilation

    "Yes, seal the gable vents up as it short-circuits the soffit-ridge air flow ... usually anyway."


    Can someone explain this idea? Building science and heat flow in general says that hot moves to cool! The hot attic air moves to the cool (relative) outside air. Having gable vents will not make air enter from outside. There may be some cooler outside air blown into the attic, but even that will not force the hot air to remain in the attic.

    The short circuiting that I do agree with is when powered vents are used, and then it does not force hot air to remain in the attic. Powered vents will draw more air from the path of least resistance, which might be ridge vents, but that still takes the hot attic air out with it.

    And please, don't fall back on "because the Mfg. says so". How many time have Mfg's been wrong!

    Last edited by Vern Heiler; 10-10-2010 at 12:09 PM. Reason: No Mfg. reason
    The beatings will continue until morale has improved. mgt.

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    Default Re: Attic Ventilation

    Attached is a basic and limited drawing showing soffit and ridge vents without gable vents and with gable vents.

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    Default Re: Attic Ventilation

    Quote Originally Posted by Jerry Peck View Post
    Attached is a basic and limited drawing showing soffit and ridge vents without gable vents and with gable vents.
    I would be interested in how the bottom right arrow is explained, and if it does exist, how it prevents hot attic air from being removed.

    The beatings will continue until morale has improved. mgt.

  29. #29
    James Duffin's Avatar
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    Default Re: Attic Ventilation

    Quote Originally Posted by Rich Goeken View Post
    Used to live in a house in NJ that had gable vents. Had to seal them because of blowing snow. Based upon some previous comments about turbine ventilators and powered ventilator systems---they may also permit blowing snow as well as rain to enter the home. Does anyone have experience with the metal or plastic ridge vents allowing fine snow to enter the home?
    I have seen some gable vents that did not have the required angle on the louvered slats to keep out rain and snow. That is due to the design of that particular vent...not a problem with the type of vent. The gable vents on my house are made so any rain or snow would have to blow up from the ground to get into the attic space. If this happens I will have more problems that snow in the attic. It will mean I no longer have gravity at my house!


  30. #30
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    Default Re: Attic Ventilation

    Quote Originally Posted by Jerry Peck View Post
    Yes, seal the gable vents up as it short-circuits the soffit-ridge air flow ... usually anyway.
    Quote Originally Posted by Vern Heiler View Post
    I would be interested in how the bottom right arrow is explained, and if it does exist, how it prevents hot attic air from being removed.

    Changing the wording from what I said to what you want is cute ... but it does not apply to what was said or was drawn.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Attic Ventilation

    Quote Originally Posted by Jerry Peck View Post
    Changing the wording from what I said to what you want is cute ... but it does not apply to what was said or was drawn.
    Not trying to be cute here Jerry. You are not the only one to support this belief of short circuiting the system, so I did not intentionally change your wording. If there is solid evidence of this being a problem, I would like to know.

    In my opinion, the short circuit theory is marketing. "Our system is not only the best, but the only way."

    The beatings will continue until morale has improved. mgt.

  32. #32
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    Default Re: Attic Ventilation

    Sorry but that simplified "bell jar" burning stick in cardboard model is a joke.

    The wind and weather is constantly changing outdoors. Heat and water loads from living space below. We're trying to ventillate (static) stratify a turbulent exchange, and exhaust heat and moisture.

    Thermodynamics is not even properly represented in that demo. Is faulty on so many levels.

    By definition, a fluid is a material continuum that is unable to withstand a static shear stress. Unlike an elastic solid which responds to a shear stress with a recoverable deformation, a fluid responds with an irrecoverable flow.

    The correct field is FLUID MECHANICS, specifically Newtonian fluid mechanics. And it isn't simple. There are few constants outdoors or in the attic.

    We never have a perfectly isolated cavity/structure. We also deal with penetrative convection in the heating months.

    Those areas prone to snow collections, we are also aiming to avoid ice dams above our no-longer by-pass ladden/poorly insulated/super heated attic spaces.

    If you want to start exploring the subject of fluid mechanics on a "K.I.S.S." level you might launch here:
    Fluid Mechanics





  33. #33
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    Default Re: Attic Ventilation

    In "my" opinion I don't think you could ever have enough ventilation. Sure the ridge vent manf. are going to say to close off the gable vents for the purpose of there intended design. But it doesn't mean it won't perform at all if other systems are in place.

    Has anyone done studies to see how much is to much? I think of it this way, since atmosphere, temp, rain snow blah blah, affects different ventilation systems differently. If one vent system performs poorly the other may make up for it. My home being a 71 had gable vents and attic fan. I have since added soffitt and ridge vent to top it off. Been that way for 5 years now. I have seen no adverse affects but the temp change from 140 to 130 or less is a big difference to me.

    Until independent study has been performed of what this thread is about you guys are just full of hot air .

    Mike Schulz License 393
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    Default Re: Attic Ventilation

    It seems some people missed this:
    Quote Originally Posted by Jerry Peck View Post
    Attached is a basic and limited ...
    What part of "basic and limited" is not understood?

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Attic Ventilation

    Quote Originally Posted by Vern Heiler View Post
    In my opinion, the short circuit theory is marketing. "Our system is not only the best, but the only way."
    Vern,

    If gable vents are currently installed, a soffit and ridge vent manufacture MAY try to sell you their product. If they DO sell you their product, what do they care if you do or do not block up the gable vents?

    They are not making or losing money on the gable vents, they are already bought, paid for and installed.

    They care because it makes their product PERFORM AS DESIGNED.

    Darren www.aboutthehouseinspections.com
    'Whizzing & pasting & pooting through the day (Ronnie helping Kenny helping burn his poots away!) (FZ)

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    Default Re: Attic Ventilation

    Quote Originally Posted by Darren Miller View Post
    Vern,

    If gable vents are currently installed, a soffit and ridge vent manufacture MAY try to sell you their product. If they DO sell you their product, what do they care if you do or do not block up the gable vents?

    They are not making or losing money on the gable vents, they are already bought, paid for and installed.

    They care because it makes their product PERFORM AS DESIGNED.
    It is my belief that marketing is aimed at selling a product for profit. Projecting the idea that what you have works, but if you add mine to it, it will work a little better, is not as effective as; what you have is no good and mine is the only way to go!

    When I can be shown that warm air does not rise because cooler air is above it, or more circulating air is worse than less, I will change my mind.

    The beatings will continue until morale has improved. mgt.

  37. #37
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    Default Re: Attic Ventilation

    Quote Originally Posted by James Duffin View Post
    I have seen some gable vents that did not have the required angle on the louvered slats to keep out rain and snow. That is due to the design of that particular vent...not a problem with the type of vent. The gable vents on my house are made so any rain or snow would have to blow up from the ground to get into the attic space. If this happens I will have more problems that snow in the attic. It will mean I no longer have gravity at my house!
    Now that is funny. I don't care who you are


  38. #38
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    Default Re: Attic Ventilation

    For the skeptics, let me try another tack, not that it will convince you to change your mind,but it might make you realize there is some considerable thought behind the theory of closing up the gable vents. At least it is food for thought.

    Think about a stove pipe, open on each end and a sealed cylinder in between painted black sitting in the sun at a 45 degree angle maybe 20 feet long on a dead calm day.
    Now it does not take much imagination to visualize cool air at the bottom being heated by the sun and rising as hot air will tend to do and exiting out the top.
    Now we know that for every cubic foot of air that exits the top there is a corresponding volume of air entering the bottom.

    Now suppose half way up the pipe we cut a hole in the side say twice as big as the hole up on top.
    What happens to the air flow?
    Does the air flow remain the same? Obviously not.
    Does the air flow at the top opening increase or decrease?
    Does the air flow at the bottom opening increase or decrease?
    Does the air flow at the opening on the side go into the pipe, out of the pipe, or both?

    Now think about a real world solution to a fireplace chimney that won't draw. One of the obvious fixes in addition to making sure it is air tight is to raise the height of the chimney. Why?

    Have to go but I'll check back after this has been batted around.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

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    Default Re: Attic Ventilation

    Quote Originally Posted by Jim Luttrall View Post
    For the skeptics, let me try another tack, not that it will convince you to change your mind,but it might make you realize there is some considerable thought behind the theory of closing up the gable vents. At least it is food for thought.

    Think about a stove pipe, open on each end and a sealed cylinder in between painted black sitting in the sun at a 45 degree angle maybe 20 feet long on a dead calm day.
    Now it does not take much imagination to visualize cool air at the bottom being heated by the sun and rising as hot air will tend to do and exiting out the top.
    Now we know that for every cubic foot of air that exits the top there is a corresponding volume of air entering the bottom.

    Now suppose half way up the pipe we cut a hole in the side say twice as big as the hole up on top.
    What happens to the air flow?
    Does the air flow remain the same? Obviously not.
    Does the air flow at the top opening increase or decrease?
    Does the air flow at the bottom opening increase or decrease?
    Does the air flow at the opening on the side go into the pipe, out of the pipe, or both?

    Now think about a real world solution to a fireplace chimney that won't draw. One of the obvious fixes in addition to making sure it is air tight is to raise the height of the chimney. Why?

    Have to go but I'll check back after this has been batted around.
    Are we trying to make the soffit vents draw (like a fireplace) or are we trying to get hot air out? The hot air that leaves the pipe half way up will not stop the air that is in the top of the pipe from continuing to the opening at the top.

    The gable vents are typically at the top of the gable, effectively making the hole in the top of your pipe larger.

    Last edited by Vern Heiler; 10-11-2010 at 08:31 PM. Reason: Bigger hole
    The beatings will continue until morale has improved. mgt.

  40. #40
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    Default Re: Attic Ventilation

    The code minimum attic venting is poor at best. Most all new construction uses soffit and ridge venting which only prevents stale air with the slow draft.
    The only time attic ventilation can be easily evaluated is on a hot sunny day and some time after noon while the sun is on the roof. This is when the truth comes out. These minimum code attics are so hot around here in the summer you have to come out and cool off before you go back up to finish the inspection.

    The best way to vent an attic is with ridge/soffit venting and with 1 or 2 powered vents depending on the attic volume. Forget square footage, when you have a large attic due to steep roof pitch you have lots of air in there that needs to be kept moving, its all about the volume of hot air.

    I have the ridge venting as a backup since these overpriced fans do fail fairly often but keep the attic temperature way below what the ridge/soffit venting alone can do. The ridge vent does not hurt the performance of these powered fans more than a few percent or any noticeable amount. I have tested this on a hot day with a 3600 sf attic with black shingles in full sun.

    As far as the gable vents being used with ridge/soffit venting, I would guess it would vary from a small amount of negative effect to a larger positive effect depending on the weather conditions. Sealing them up would be a waste of effort.

    Bruce King, B.A. King Home Inspections, LLC
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    Default Re: Attic Ventilation

    What happens when you take that stove pipe with the hole cut into it and blow air INTO that hole cut in the side of it?

    What happens to the air in the top part of the pipe?

    What happens to the air in the bottom part of the pipe?

    What happens to the amount of air entering the bottom of the pipe?

    What happens to the amount of air exiting the top of the pipe? And where does that air come from?

    Now make that hole through the side of the stove pipe all the way through the stove pipe, so you can blow air *through* the stove pipe, now what happens when ... (repeat above questions under this condition, which is the condition you would have with gable end ventS).

    Jerry Peck, Construction / Litigation Consultant
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  42. #42
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    Default Re: Attic Ventilation

    Quote Originally Posted by Jerry Peck View Post
    What happens when you take that stove pipe with the hole cut into it and blow air INTO that hole cut in the side of it?

    What happens to the air in the top part of the pipe?

    What happens to the air in the bottom part of the pipe?

    What happens to the amount of air entering the bottom of the pipe?

    What happens to the amount of air exiting the top of the pipe? And where does that air come from?

    Now make that hole through the side of the stove pipe all the way through the stove pipe, so you can blow air *through* the stove pipe, now what happens when ... (repeat above questions under this condition, which is the condition you would have with gable end ventS).
    Tried to figure out the multi quote, but don't know how it works. Doesn't matter though! Answer the first part and the rest is irrelevant.

    "What happens when you take that stove pipe with the hole cut into it and blow air INTO that hole cut in the side of it?"

    Why would cooler outside air blow into the hot inside air of the pipe? And if cool air was blown into the pipe, what is the problem? Its "cooler" air! And remember, the gable vent is at the top of the theoretical pipe, not the middle.

    The beatings will continue until morale has improved. mgt.

  43. #43
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    Default Re: Attic Ventilation

    Gable vents intake air as well as vent air to the exterior. If the home has ridge vents as well the worse case scenario would be the air drafts thru the attic and out the other gable vent. On the stale, dead hot air days the air will slowly drift up from the soffit vents and out the ridge. In those days the gable vents do not play a major part. That is why I always suggest that a ridge or a couple turbine vents be added so the air does draft straight up and out the roof.

    Air interrupted....so what. It is going to go out somewhere. As far as the ridge vents altering anything to do with the gable vents, it just is not happening. Keeping the gable vents is not hurting anything.

    I will have to agree with everyone about the attic being cooler with addded roof top vents whether they be turbine or ridge. I also recommend that if there are just gable vents they should add a ten foot stretch of ridge vent in the middle or add a couple turbine vents splitting the difference across the roof. On every single occasion that I have checked afterward the air was much cooler in the summer by 10 to 15 degrees. As far as snow blowing in the attic with gable vents...that would be the gable vent design not just an inherent flaw in all gable vents.

    Ridge vents alone from my experiences in installing or monitoring, they just do not draft as well and the attic is much hotter. Usually with these multi faceted roof designs today there is not any nice long section to add the ridge vents. There is alwys to many places for the air to get trapped and not draft out like it should. A combination, depending on the roof and attic, is always the best from what I have experienced.

    The idea that in an upper roof with ridge vents and a lower section of roof with a turbine vents cancels out the soffit vent is also false. Once the draft starts and the ridge does pull up from the turbine vent it is drawing the lower air as well behind it. I have seen that set up in many homes and it works quite well. Then all areas of the attic are drafting properly and there are not hot spots in the attic. (hotter than others areas that is)

    Some folks hate going into attics. I don't. It is one of the most involved areas of the home. There is so much going on to investigate and to write.


  44. #44
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    Default Re: Attic Ventilation

    Quote Originally Posted by Vern Heiler View Post
    Why would cooler outside air blow into the hot inside air of the pipe?
    One word: wind

    And if cool air was blown into the pipe, what is the problem?
    One word: pressure

    Its "cooler" air!
    One word (okay - "two" words): air currents

    And remember, the gable vent is at the top of the theoretical pipe, not the middle.
    I guess you have not seen gable end vents *not* "at the top" (your words) of the gable?

    Besides, Jim said half way up, I didn't, I was going with a hole through the side of ... go back and read my post. I have seen very few gable vents "at the top" of the gable end, usually somewhere above the center to upper third, but very few, if any, "at the top" of the gable end.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Attic Ventilation

    Quote Originally Posted by Jerry Peck View Post
    One word: wind



    One word: pressure



    One word (okay - "two" words): air currents



    I guess you have not seen gable end vents *not* "at the top" (your words) of the gable?

    Besides, Jim said half way up, I didn't, I was going with a hole through the side of ... go back and read my post. I have seen very few gable vents "at the top" of the gable end, usually somewhere above the center to upper third, but very few, if any, "at the top" of the gable end.
    Showing off with the multiple quotes!

    All of those words are good in my opinion, except "pressure".

    Wind and air currents do just what we want. Move the hot air out. If wind is what blows into one gable vent to create air pressure, then there is most likely wind at the opposite gable vent creating a vacuum.

    Other than dormer vents the only place I see gable vents is at the top of the gable wall.

    The beatings will continue until morale has improved. mgt.

  46. #46
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    Default Re: Attic Ventilation

    Quote Originally Posted by Vern Heiler View Post
    Showing off with the multiple quotes!


    Type this (but leave out the extra spaces) and you can make multiple quotes too: [ quote ] to start a quote and [ / quote ] to end a quote, thus you could do this: [ quote = Jerry Peck ]Blah, blah, and blah.[ / quote] and, by leaving out the spaces, get this (note, I typed 2 spaces between my name, simply a space where there is a space, which will leave 1 space between my names):
    Quote Originally Posted by Jerry Peck
    Blah, blah, and blah.


    Wind and air currents do just what we want. Move the hot air out. If wind is what blows into one gable vent to create air pressure, then there is most likely wind at the opposite gable vent creating a vacuum.
    You are getting there, slowly ...

    If the wind blows in one gable end, the air will not only try to go out the other gable end, but it will also try to go out the ridge vent and the soffit vents, depending on where other wind (wind=pressure - there is that word), its strength and direction.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  47. #47
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    Default Re: Attic Ventilation

    Quote Originally Posted by Vern Heiler View Post
    Other than dormer vents the only place I see gable vents is at the top of the gable wall.

    "at the top" or 'near' the top?

    Makes a difference.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  48. #48
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    Default Re: Attic Ventilation

    Quote Originally Posted by Jerry Peck View Post
    "at the top" or 'near' the top?

    Makes a difference.
    Not to the hot air that is leaving .

    (How was I gonna multiple quote that?)

    Last edited by Vern Heiler; 10-12-2010 at 08:45 PM. Reason: quotes
    The beatings will continue until morale has improved. mgt.

  49. #49
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    Default Re: Attic Ventilation

    Bruce King, B.A. King Home Inspections, LLC
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    Certified Master Inspector, Independent Inspectorwww.IndependentInspectors.org

  50. #50
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    Default Re: Attic Ventilation

    Quote Originally Posted by Larry Hood View Post
    In an older home I was told that the gable vents should be sealed.The attic has R-30 insulation,a ridge vent and soffits that are vented.Came you advise me if this is a good or bad direction.
    It is depending upon the system in place and how the attic was insulated and any upgrades to the attic and home as a whole.
    In normal circumstances the gabble vents will be left alone and used to allow the attic to dissipate any heat, humidity, condensation that have built up during severe weather system that affect an attic from time to time.
    Yes saw-fit venting also play a roll as do ridge venting.
    To me those gable vents are to be left alone until you have solid evidence that the home was made weather and air tight.
    The gable vents would have been addressed then.
    Then there would or might be a reason to close off those gable vents.

    Last edited by ROBERT YOUNG; 10-22-2010 at 07:17 PM. Reason: edditingyou wil get use to me sorry learning.
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  51. #51
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    Default Re: Attic Ventilation

    Most of the people who have posted replies are from warm climates. When I have 2 feet of snow on my roof, the ridge and/or roof louvers aren't doing a thing for ventilation. Properly constructed gable end vents will keep out the rain and snow, and won't be blocked by snow either.


  52. #52
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    Default Re: Attic Ventilation

    Quote Originally Posted by Fred Weck View Post
    Most of the people who have posted replies are from warm climates. When I have 2 feet of snow on my roof, the ridge and/or roof louvers aren't doing a thing for ventilation. Properly constructed gable end vents will keep out the rain and snow, and won't be blocked by snow either.
    Please read and look at Bruce Kings links to the questions being asked here.
    I am going to say no matter what climate you live in venting does help.

    Robert Young's Montreal Home Inspection Services Inc.
    Call (514) 489-1887 or (514) 441-3732
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  53. #53
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    Default Re: Attic Ventilation

    Quote Originally Posted by ROBERT YOUNG View Post
    Please read and look at Bruce Kings links to the questions being asked here.
    I am going to say no matter what climate you live in venting does help.
    I am not saying do not to use ridge vents and louvers, just that the gable end vents are some added insurance.


  54. #54
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    Default Re: Attic Ventilation

    Quote Originally Posted by Fred Weck View Post
    I am not saying do not to use ridge vents and louvers, just that the gable end vents are some added insurance.
    Very good point

    Robert Young's Montreal Home Inspection Services Inc.
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  55. #55
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    Default Re: Attic Ventilation

    Seal everything up!

    Go with foam!

    Condition the attic!

    End of discussion.


  56. #56
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    Default Re: Attic Ventilation

    Quote Originally Posted by Wayne Carlisle View Post
    Seal everything up!

    Go with foam!

    Condition the attic!

    End of discussion.
    However, as HI's we are charged with determining, functioning as intended or not functioning as intended. Acceptable or not acceptable.

    In NC we can suggest improvements but must not recommend improvements. Conditioned attics are a definite improvement in my opinion .

    The beatings will continue until morale has improved. mgt.

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