Attic Ventilation

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  1. Ed - I live in the Dallas area and am getting ready to install a new roof. I plan to have the decking replaced with radiant barrier decking. The house faces north with the main section running east/west. There is a south facing 2 car garage and a south facing extension of the master bedroom. Both of these have roof extensions coming from the main east/west roof. There is currently about a 1600cfm electric fan on the main roof and another of approximately 1200 cfm on the garage roof. There are large gable vents on the east and west ends of the main roof and a large gable at the south end of the garage roof. The master bedroom is just an extension with no gable vent. My question is what kind of ventilation do I need? If I leave all the roof vents off and add additional soffit vents, will the large gable vents exhaust the heat adequately? The gable vents are probably 10 - 20 ft. long by about 3 ft. high and extend to the peak of the roof.

    Ideally, you would have plenty of soffit vents for air to enter and then exit though the fans. Most likely, you have air entering through the gable vents and exiting through the fans. This creates good airflow through the top of the attic but you don't get the "in the bottom out the top" which is preferred. I'm not big on electric fans and they probably will be overkill after installing the radiant barrier decking which will greatly reduce the heat in the attic anyway.
    The best ventilation method would be to have plenty of soffit vents and then block the gable vents and either go with several 14" wind turbines or a high-profile baffled ridge vent. This will FORCE the air to come in the bottom and out the top. You've got pretty big gable vents, but I'd probably lean towards the ridge vents while a new roof is being installed.


    If you have access to the inside of the walls (from the attic space), then yes, you can staple the foil directly over the insulation, across the rafters.

    If you haven't put the sheetrock/drywall on yet, then I recommend you watch the 3rd video down on this page, called "How to Install Radiant Barrier in a Cathedral Ceiling" and install it that way. Go with foam strips like in the video and afterward you can put in R-19 insulation. Then, if you REALLY want to insulate, put 3/4" foam board on the bottom of the rafters BETWEEN the sheetrock and the rafters. This will significantly reduce "thermal bridging."

  3. I have corner areas in the attic which are so remote that ventilation is nearly impossible. What to you suggest in the installation method for those areas: lay over insulation or staple to rafters? Will the lack of ventilation effect the foil's performance?

    You have a couple of choices. Lack of ventilation does not effect the foil's performance, it effects the attic as a whole in the ability to help move heat outside. So if you don't have great ventilation in a limited area, I would not worry about it. You can either lay it out or you could staple it up but let it "droop." This would allow a little more airflow over/under the radiant barrier.

  4. I installed a gable fan and am also wanting to install a radiant barrier. The insructions for the fan say to cover the vents closest to the fan so the fan can pull the air fron the other side of the attic. When installing the radiant barrier do I still need to plug the vent holes closest to the fan?

    Yes, you want to allow the airflow to circulate as if the foil isn't even there. For more information, check out one of my newest videos about installing AtticFoil radiant barrier and the recommended air gaps around the foil.

  5. Ed: I have a large attic with soffits all along the 36' length of the house, front and back, and a ridge vent all along the roof. With that type of ventilation, would reflective paint or foil help much?

    Your attic is just like your car and ventilation (which you have) is like rolling down the windows of your car. It helps, but if the car is in the sun it STILL gets hot due to radiant heat gain. Installing AtticFoil® Radiant Barrier Foil is the most effective method to stop heat gain; just like parking your car in the shade would help with the heat gain, radiant barrier it is like putting the roof of the house in the SHADE from the HEAT.

    How much will it help? If the roof gets hot, it will help a lot. If the roof is in the shade and does not get hot, then it will have limited benefit. You can call us at 800-595-8772 with any more questions.

  6. Do I need an attic fan if I have proper attic holes: Low and high? I am installing a new roof with comp, I will spec an radiant barrier, we already have attic insulation.

    Most customers opt for a passive ventilation system which is just a combination of working (ie. clean, unobstructed) soffit vents and either a ridge vent or a pair of gable vents; oftentimes nothing more is necessary. Once a radiant barrier is installed, your attic air temperature should be within 10 degrees of outside air temperature. If it's not, then more ventilation is probably the next step.

  7. I am going to do a vinyl siding job soon. I have read a number of articles about radiant barrier products. Questions: Our typical exterior remodel consists of old siding tear off--apply 1 inch Dow brand foam board with taped seams--apply a house wrap--after the wrap is that when I should apply the radiant barrier or should I put that on first before the foam board goes on? In the attic should I do a layover on top of the attic insulation or should I staple to the underside of the rafters instead?

    You should apply the radiant barrier OVER (after) the housewrap - you want it to be the LAST layer before the battens and the siding. Take a look at the second to last row of photos on this page: DIY Radiant Barrier Customer Installation Photos

    In the attic it's hard to say without some more details from you; installation is not based solely on where you are located, there are several other factors that determine the best installation method for your home. Every home is different, so while there are general recommendations for certain climates, sometimes one method is best for a particular home. To determine which installation method would be best for your home, I'd recommend you read this article on our website: Best Radiant Barrier Installation Method

    Read the article and consider your situation and then decide. Either way you go, the first layer of foil is going to offer you the benefit of blocking 97% of the radiant heat gain that you are currently allowing all 100% of it to enter the home. The difference between 100% heat gain and 3% heat gain is tremendous, not only for comfort but for energy savings as well.

  8. I am preparing to reroof with metal. My house has no overhang for soffit vents. I have one gable vent at the front of the house. I have no ridge vents, but currently have a power attic fan. I want to eliminate the attic fan and use ridge vents. My question: Is one front gable sufficient of air intake? If not, is there an edge vent system that works with metal? Thank you, Sandy Bourdon

    Most customers opt for a passive ventilation system which is just a combination of soffit vents and either a ridge vent or gable vents; oftentimes nothing more is necessary. Once a radiant barrier is installed, your attic air temperature should be within 10 degrees of outside air temperature. If it's not, then more ventilation is typically the first place to start.

  9. This question is in regards to new construction. Part of the project is for a detached 30' x 54'garage that will have manufactured attic trusses for a habitable room over the garage. The roof design is a simple 8/12 pitch gable. The insulation sub recommended using closed cell foam and blown cellulose at the top portion of the trusses to get the mandated R-38. This is great for R value, but now I can no longer use a soffit vent/ridge vent combination because the airflow to the ridge is now blocked by the closed cell foam. Making the entire roof a "hot" one would be the easiest but would add about $7000 to the bid. Yikes. We know proper ventilation for the cold section of the garage roof is essential. What are some realistic options? Thanks for your time. Don

    Foam is a great insulator, but it only works to slow conductive heat flow, not radiant heat flow. Is this garage going to be conditioned? Where are you located? Send me an email at support(at) so we can get some more details from you and help give you the best advice for this situation.

  10. Ed: I live in Southern CA and want to place a Solar Powered Attic fan in my single story, S tiled roof. My home is positioned with a front roof vent facing North West, and the back facing Vent facing South East. What is the best position of the fan to get best air current for mounting an attic fan? Thank You. Marv

    I'm not a big fan of solar fans since they are expensive and quit working as soon as the sun goes down. I'd rather have two wind turbines that will pull MORE air and work 24/7.
    I'd install a radiant barrier and THEN decide if you need more ventilation. Measure the air temp in the attic. If it's MORE than 10-20 degrees above outside air temp, then add more ventilation. Essentially the air is getting "stuck" in the attic like a clogged drain.

  11. I live in Atlanta, Ga. and have a 10:12 shingle Hip roof that faces South with full exposure to the sun. The other areas of the roof are shaded and do not get as hot in the summer. Can I install the Radiant Barrier to the rafters on the Southern exposed roof and not the Northern side? Or do I need to cover 100% of the exposed attic. Thank you, Tim Richardson Atlanta, Ga.

    Partial coverage works with radiant barrier. If one side is not getting sunlight at all, then you can simply cover the sides that do have sun exposure.

  12. We recently had our roof redone in a house that is about 100 years old. There was no ventilation in the attic areas. The roof is heavy clay tile. The roofer used a underlayment material that creates a vapor barrier in the attic. The roofer said that this is not a problem. We were told that a form of insulation or radiant barrier would be a good idea. We are thinking of having a radiant barrier put in (tacked on the bottom of the rafters) and we asked about the lack of ventilation problem (moisture problems causing mold, etc) and the company representative said the lack of any ventilation is no problem. Another insulation person said that the only thing to do is put up a bifold material covering all of the rafters and shooting cellulose into the area between the bifold material and ceiling and this will prevent any moisture problems. Which is correct?

    Thanks for the question.
    I really need more information. If you are in Arizona, then I would say it's not a problem. If you are in New York, then it could be a problem.
    Where are you?
    Do you have any soffit/intake vents?
    Do you have ANY method of installing ventilation?

  13. Ed-I have talked to so may people-all say something different. I live in Maryland, house is 33 yrs old, a 40 foot by 26 foot 2 story with a very narrow ridge vent and 2 14x24inch gable vents.I want to do both 6 inch circular soffit vents and radiant barrier then add more insulation later when we can afford it. What type of product(if any) do we need to funnel air from our new soffits to behind the barrier to the ridge vent OR leave a 6 inch gap at the bottom so air flows throughout the attic space & not just behind the radiant barrier? I have seen Accuvent (and other stapled shields that don't allow any air into attic space) but if these are not needed-what type of smallish product do I buy just to keep insulation away from soffit vent? Or do I need a 48 inch shield that runs from the soffit to be stapled 30-40 inches up between the radiant barrier and the roof deck? I talked to at least 5 different people-all from different jobs(sells soffit vents, sells insulation, etc). I watched all your viseos and read all these questions and haven't seen any thing to address the "insulation dam" factor....also called rafter vents I think. What do I really need?? Thanks for your videos-you have really been a great help to so many people.

    A simple gap at the top and bottom of the staple-up run will address the air flow from the soffits into the attic space. I made a video talking about air gaps here:
    As far as the vents go - I don't think they are necessary. If you think you will blow in insulation in the future and your concern is clogging the soffits with the new insulation, then try the SKIRT method with the foil - it can be found on this page, about halfway down:

  14. I have a 1700 sq ft home located in Austin TX. The house came with a centrally located attic fan but the motor burned out some time ago. When I had a new AC unit installed some 14 years ago, the guy gave me a foam barrier for the fan louvers, and told me to keep it covered when the attic fan wasn't actually being used. Now I am thinking I might want to keep it open, using the logic that "heat rises, so having the louvers open will allow the heat a chance to escape the house." On the other hand, when the louvers ARE open, I can feel the heat radiating down out of them, leading me to think that the first guy was right and I should prevent the heat from radiating out to the rest of the house. So -- should I keep the louvers open, or keep them closed? thanks!

    Just to clarify, hot air will rise but HEAT itself does not necessarily rise. Heat has a unique property in that it moves from areas of HOT to areas of cold (or the absence of heat).
    Now, it sounds like you are talking about a whole house fan... if this is the case, then when you open the vents that heat is attracted to the cool interior of your home and would therefore migrate to the inside of the home. The reverse would be true in the winter - if you open those vents in the winter, the heat inside your home is going to be attracted to the COLD areas above the vents and will migrate out the vents, making it harder to keep heat inside. I recommend keeping them CLOSED as the installer suggested.
    If you are trying to cool off the attic (and the house) then you need to consider installing a radiant barrier if you do not have one. Doing so will prevent 97% of heat from even entering the attic space and thus the home via the roofline and this is going to have the biggest impact on comfort for you during the summer and wintertime.

  15. Our house was built in 1949. There is no overhang/soffits. There is a gable vent on each end. We are in North Dakota and get terrible ice dams. We found there was no insulation in the floor of the attic spaces and we added that which helped but still pretty bad dams. There was very old insulation between the rafters in this area so we have now removed that which seemed to help the temperature come down in there in the winter but we know it's still not quite right. I'm hearing a lot about intake vents so I'm wondering.....we don't have those. It gets very hot in there in the summer and we do have some humidity so I worry about the moisture even in the summer. Any ideas for us?

    Using radiant barrier in your attic will reduce radiant heat coming from the home, preventing the warm air from getting into the attic and forming the ice dams. The key to preventing ice damming is to SEAL, SEAL, SEAL - any heat escaping from the home is a potential contributor to ice dams forming. I'd lean toward the "over insulation" method for your area:

    You also want to make sure your attic is well ventilated - so adding intake vents is a good idea. This will keep the attic cold and thereby keep the roof cold; by doing this you can prevent ice damming. So keep the warm air in the house and keep the cold air in the attic! Take a look at this case study as well, it's from a guy who had the same issues with ice daming and how he addressed it: Ice Damming in NY Fixed with Radiant Barrier

  16. I live in Massachusetts in an older house with a hip roof and about 1000 sq. ft. of attic space. Ventilation consists of a powered roof fan at the top with soffit vents. The thermostat/humidistat is set at 100 deg. in the summer, 70% in the winter and works well maintaining those settings.The problem is that in the summer the rooms below are hot and I was hopeing that a radiant barrier would help. The attic floor consists of 6" of lose rock wool insulation over horsehair plaster ceilings with no vapor barrier. Can I lay the radiant barrier over the rock wool, (under the floor boards because I use the attic for storage), without worrying about trapping moisture underneath in the insulation below.

    No, unfortunately you cannot do this because eliminating the necessary air gap means the heat is not radiant, it's conductive. A radiant barrier does not stop conductive heat flow, only radiant heat flow. In this situation you would be better off stapling up the foil to your rafters since the floor space is occupied. Otherwise, the foil would only work in the areas where it was applied to the plywood floor and OPEN to the attic air (ie. nothing stored on top of it).

  17. Hello, I have a Cap Cod from the 1950's. I want to add a radiant barrier. Can I put foil ontop of foam boards that will go up in the slopes between the sheathing and the cieling of the 2nd story bedroom as long as I leave a gap for ventilation. also can I put a vapor barrier on the other side so it will go from inside out(between rafters in slopes); drywall, vapor barrier, foam board, radiant barrier, 1-2 inch gap for ventilation, and sheathing.

    Yes you can create foil-faced foam board to block heat from the roofline from coming in through the cathedral ceiling so long as the FOIL side is facing a clear, unobstructed air gap. As far as adding a vapor barrier into the assembly, if you are in a cold climate, then you will be ok adding a vapor barriers where you suggested in the layering.

  18. We are building a new 3600 sq ft home in the Phoenix area. The builders are adding a radiant barrier roof in addition to r-30 insulation. They offer r-38 as an upgrade for $480. Would it be worth it to upgrade to the high rated insulation?

    That is hard to say because a lot of times once people add a radiant barrier they find that it makes the insulation they have much more effective so there is no need to add more. I would look at the Department of Energy's website for the recommended level of insulation they suggest for your geographical area and as long as you are within those parameters you should be fine.

  19. I have a good sized attic that I would like to finish and use as living space. I had somebody tell me that I could put 1x1 or 2x2 boards in between the rafters and stretch the reflective barrier across those between each rafter and put insulation then wall board. I don't have soffit vents all I have is gable vents on the east and west but he told me I could close those off eliminating the need for vents. Is this correct?

    The best way to approach this is to gain access to the ceiling/walls of the room and add radiant barrier, along with insulation, via the Cathedral Ceiling install method.
    In the Cathedral Ceiling installation method the air inside the assembly is not vented/ dead air; but there is no risk or damage from "holding" the hot air in the wall. Just keep in mind that the total assembly will probably be a little warmer since it does not have the ability to vent some of the heat.

  20. I am a widow, living in Texas Panhandle. My home is 1600sq.ft. and is older. My house is too warm, i installed radiant barrier insulation a few months ago.My ventilation consists of 4 passive roof vents and 10 soffit vents. What type of more ventilation do I need, I'm confused. Please help! AC bill is very high!

    Well the attic should be properly ventilated, but if you have a radiant barrier installed the attic air isn't what will contribute to your home getting too hot, it's the SURFACE temps that make it uncomfortable. Do you have a lot of exterior walls that catch sunlight? How about your windows - do you have a lot that the sun shines though? Since you have addressed the roof line with the radiant barrier - the next practical thing to consider are other areas of radiant heat gain that are making the home hot. The attic ventilation is important to keep the attic dry, but again, this isn't likely the source of your problem.

  21. I've been searching the internet and have not found a video of anyone installing a radiant barrier above a vaulted ceiling. Most of my house is vaulted and I am not sure how I'm going to move around on top of the vaulted ceiling and keep from smashing all the blow in insulation while I'm installing the radiant barrier to the roof structure.

    Typically when you have access to the back side of the vaulted ceiling from inside the attic, the best way to apply the foil is to lay it directly on top of the vaulted areas. This prevents the heat from entering and escaping (summer and winter benefit) and it eliminates the need to get above the area and risk falling.

  22. I am having a roof extension done on my home to cover a large portion of our deck. There is no attic, but we do have soffits, with can lights. Do I need soffit vents?

    Typically porch areas don't have ventilation systems since they are pretty flat roofs and open to air on all sides.

  23. I live in the Northwest part of friend & I plugged 6 out of 8 eave vents with 14" x 7" pieces of cardboards in our new house because we were burning 20 gallons of heating fuel in 8 to 9 that a mistake? I am inquiring on this confusing topic...please let me know. Thank you!

    I'd need more information to say for sure but if you were having trouble keeping heat in the home, plugging up your attic ventilation is not the way to stop that heat loss. First you need to make sure the home is sealed air tight. If it is a new home, it is generally safe to say this should already be done. Then, you need to add a radiant barrier over your insulation on the attic floor so you can stop convective looping in the insulation and help the home retain its heat. The ventilation in the attic should not be altered - you need this to prevent ice damming and to keep the attic dry (prevent moisture accrual). For more information on using a radiant barrier in the attic to retain heat, please see the installation information on this page: Installing Radiant Barrier Over Existing Insulation

  24. Should turbine vents be covered with burlap during the winter in Arizona southwest to retain the heat? Everything I read says not to because of moisture and snow... both of which we have a severe lack of in AZ... so is it worth covering the vents in dry climates?

    No, your attic vents should not be covered. If you're trying to reduce heat loss from the home into the attic, you need to consider adding a radiant barrier over your insulation to help the home from radiating heat into the attic space. More information can be found here: Installing Radiant Barrier Over Existing Insulation

  25. Hi Ed, I live in Panama, on the Pacific coast, in the "dry belt" -- which means year-round 90f temperatures, about 8 months with some heavy rains, 4 months with no rains. House is about 5 yrs old, concrete block uninsulated, hipped/gabled roof of about a 30degree pitch, maybe 1800 sqft of attic space, some of which is over patios. Roof is corrugated sheet steel with corrugated clay tiles. Most days some gentle breeze to maybe 10knots. No roof vents to speak of, although around the bottom edge, I can see a lot of daylight leaking in out at the far ends. At night, house can be 15-20F hotter than outside. We tend not to use the air conditioning very much. How can I determine whether I need a whole-house fan (to suck hot out of the attic by sucking hot out of the house, let doors & windows let cooler outside air come in), or just roof cavity (attic) vents (soffet and passive, or turbines, or ?) Any ideas?

    If the HOUSE is hot, you need cool air flowing THROUGH the house to get it to cool down. You would need a whole house fan. A Radiant Barrier will help keep the home from GETTING as hot in the afternoon. We have many who have NO air conditioners. The homes cool off at night, but the radiant barrier helps to keep the home from maxing out in the afternoon.

  26. I have an old house with a new roof shingles. I want to insulate my living in attic space with a radinate barrier. My houses dose not have any vented soffits, just vented gables on both ends of the houses. Would a radinate barrier work with no vented soffits

    Regardless of your ventilation, the foil will still work to block 97% of radiant heat attempting to enter the home as long as when you install it there is an air gap on at least one side of the foil.

  27. Great blog, Ed. I'm in NY with a 22x22 attached garage which has unfinished attic space that I am finishing. Garage has ridge vent. The ridge runs perpendicular to the house, so there are soffits on side away from house but none where the garage/attic abut the house. Side away from house is easy: radiant barrier, insulation, drywall. What do I do on the half abutting the house? Just radiant barrier? If RB+insulation+drywall, where do I get intake from? Thank you for your help and great blog.

    Thanks for the question. Since you are finishing the attic space above the garage, I recommend you install the foil as shown on this page:
    It allows for the air gap needed for the foil, plus regular insulation before the drywall. The air in the cavity still be able to move a little bit. If you're able, you can open up the soffit vents to get better movement through the space, but it would work regardless.

  28. I bought a house that was gutted and redone. The problem is the roof or attic has absolutely no ventilation. My house has fake eaves and they vaulted the ceilings. However we have 7 foot walls instead of 8 foot which is why that left no room for ventilation or for the hot or cold air return ducts to be insulated properly. We now have condensation buildup in the attic from where the hot and cold air meet. We know have a smell of mold/mildew in our home. My room is also junk and it's only 6 years old. I live in Illinois. Do you have any suggestions on where to begin to fix my problem? Any suggestions would be greatly appreciated.

    I would start by removing any insulation that is molded or mildew smelling and replace it with new, dry insulation once you add ventilation. Ventilation works in two parts. First, you want the interior of the home sealed so it does not leak air into the attic space (this is the main source of condensation) and then, secondly, you want plenty of air moving through the attic space so that the condensation or moisture that might exist will evaporate because of the air flow. It's a delicate balance, but it's not complicated. Have you thought of contacting a home energy auditor? They might be able to help you get started or at least identify the problem areas.

  29. I am building a new detached garage with upstairs living space. I am going to install to velux skylights. Do I need to have soffits or gables. I don't want to waste energy by letting cold air enter in the winter through knee walls. The garage will be 22x 26. What suggestions do you have t,o insulate or vent most efficiently? Yank you very much!

    If the entirety of the space above the garage is going to be living space, then you don't have to vent it. It can be sealed air tight - which is how it is done if you will be conditioning this space. As for the garage however, you might want to add either a window or some way to vent it out since it can gain radiant heat from any walls (including the garage door) that catches sunlight.

  30. Greetings, I am considering attic insulation. What is the best way to install Attic foil in my attic. I do not have a ridge vent but have 4 roof vents and a solar fan in the roof. Would it be best to add 1/2 strips across the rafters to create cross air flow then completely cover attic down to the gable vents. Or go across the rafters down to the gable vents and cut openings where the roof vents and solar fan are? Or should I rethink the process? Thanks Ed

    You can just staple the foil up on the underside of the rafters and then cut around your roof vents and your solar fan. It's that simple! Install instructions here:

  31. Hi. I live in Chicago and I have a 24'x24' gable garage with a ridge vent on the room and two octagon windows on either side that do not open. I am looking for the best way to cool the upstairs so that things I am storing do not get ruined accidentally. I've read numerous article about electric attic vents and they seem to be on the fence when using those with a ridge vent. I thought about replacing the windows to ones that I can open...... I also found this GF-14 Garage Fan & Attic Cooler by Americas Best and was wondering if you had any experience with this. Do you think this is a solution? If it is, Do you know of anything similar that is a better product for the money? Any help would be greatly appreciated. Thanks.

    Well if you're trying to cool the AIR up there, then ventilation is your key. However I can tell you that venting the space will not prevent your stored items from heating up. Rather you need to block the heat so the SURFACE temps (the temps of items in the attic) drop and things stay cooler that way. The best way to do this is to get a radiant barrier stapled up there under the rafters. Watch our install video on this page to get a better understanding on why this makes the biggest difference:

  32. Hi Ed We are putting on a Drexel aluminum standing seam roof next week and had problems finding a aluminum motorized fan. We have a 1960 brick house with a hip roof and 1600 square feet attic.We finally found a Lomanco exhaust fan and was told we need two fans for our attic space. We wanted aluminum only especially because it would be difficult to replace housing if it deteriorated after the roof was installed. We live on the water and because of the high winds we will use mechanical fasteners on roof. Do you agree that both fans should be on one side avoiding counter winds. We will have soffit venting But it won't be (100%) continuous. Please give us your thoughts . Thank you

    I think one fan should be enough; set it to 120 on the thermostat so it won't run continuously, round the clock. I really think you should consider radiant barrier for this application as well since it will block 97% of the heat coming off the roof and greatly improve the interior temperatures of the home.

  33. I am considering installing a radiant barrier in my attic in San Antonio Texas and I just got an estimate that was pretty high. The salesman said he would need to install a ridge vent in our roof as well to let the hot air escape through the top but we do have turbine fans in their too. Question is do we need a roof ridge vent installed in order for the radiant barrier to work or will the turbines accomplish the task?

    The exhaust vent can be as simple as a static vent or wind turbine, you don't have to have ridge vent in order for the foil to work. In fact, the foil will work with NO air movement, so long as there is an air gap. This is why foil works in wall systems that are sealed and have a dead air space. If they can't be forthcoming with you in the estimate stage, I'd carefully consider that before choosing to work with them.

  34. I am located along the southeast coast of N.C., and just had a radiant barrier installed in my attic, with the foil stapled to the bottom of the roof rafters. Regarding ventilation, the existing gable vents were closed off before the foil went up, with the plan to soon install a ridge vent (which, I am told, will provide a better air flow than the gable vents would have). There are soffit vents (for air intake) along the entire 36' of eve both front and back of the house. How do I determine the appropriate length of ridge vent to install? (We will probably be using Owens Corning Black Composite Ridge Vent.)

  35. Hello I have some old plaster and lathe ceilings that I would like to attach a radiant barrier to. Could I then attach some furring strips over the barrier, and drywall to create a small airspace without concern for condensation or mold forming in the future. I saw your post referring to this method for cathedral ceilings but was wondering what would happen if I applied this method over the existing plaster. Thanks John

    You can do the cathedral ceiling method as you suggest, just make sure you use a PERFORATED radiant barrier foil, not a solid vapor barrier. It's very hard to keep moisture from forming, especially in older homes. You basically just want to provide a drying method to keep things dry.

  36. I am doing some renovation in New Orleans, LA. I plan to install Radiant Barrier in the attic according to recommendations. I'm not about to get in the attic for that until winter and the roof will be going up in a couple weeks so I can't wait to see what attic temperatures are like after the Radiant Barrier install. I currently have approximately 2,000 square feet of attic space and 1 power fan for attic exhaust. I will be adding on approximately 1,000 square feet of attic space for a total of 3,000 square feet. I was planning on removing the powered fan and replace it with ridge vents, however, I only have about half of the linear feet needed on my ridge to satisfy the 1/300 rule for exhaust ventilation. Is that ok since I will also be installing the Radiant Barrier in a couple months, or should I keep my power exhaust fan and possibly add more exhaust fans instead of ridge vents?

    You don't have anything to lose by getting the foil up and then going from there. If it were me, that's what I'd do install the foil (according to the instructions whereby you don't block any of your exhaust vents/fans) and then decide if you need/want more ventilation.

  37. I am installing radiant barrier. There is a powered thermostatically controlled attic fan and a single gable end vent, there is not a ridge vent and the soffit vents are minimal as the house was built in the late 60's. Should the RB be installed as normal to within about a foot of the ridge and cut out around the fan...or is there a different method for such an attic situation?

    It needs to be installed as directed on the install page - gaps at top and bottom and cut around for clearance of all vents/fans/etc.

  38. Hello Ed, I would like to demonstrate the operation and effectiveness of my new ridge vent system. My initial attempts to actually see, or at least smell, smoke drawn into the soffit vents and exhausted out at the ridge, were inconclusive, because even a gentle breeze overcomes the draw of the vent (if any), and because I have not found a good source of steady, high volume smoke (candles, matches, paper, and incense don’t seem to be adequate). Do you have any suggestion for smoke or other tests to demonstrate the ridge vent system operation? The relevant attic venting parameters are indicated below: • 3000 square foot attic, with 4:12 roof pitch over long ranch house • The soffits are not blocked by insulation • I have a total Net Free Venting Area of 2,800 square inches, with 60% at the soffits and 40% at the ridge • Total length of the ridge is about 94 feet, and I have 47 soffit vents. Thanks for your help in advance....Paul K.

    A “smoke grenade” from a fireworks stand will work great, or even the smaller smoke bombs.
    I recommend dropping them in a METAL bucket if you are doing this inside the attic. Have fire extinguisher and bucket of water/wet towel ready just in case.
    Another option is to do an internet search for “high volume smoke emitters.”

  39. I have an 1880 Victoria house high in the mountains in Colorado. How do prevent ice dam build up on the roofs edge? The house does not have soffit vents nor any way to create them. There is no eaves. I have R38 batts insulation in the ceiling of the attic. There is a ridge vent with no gable vents. How would I install a radiant barrier to alleviate the ice dam build up on the interior of the attic roof?

    Ice damming is caused when the top of the roof warms above the freezing point and the lower part of the roof is below freezing. To prevent ice damming, you want a COLD roof. The roof gets warm due to warm air leakage into the attic from the house AND from the home emitting radiant heat.

    A radiant barrier installed in the attic will help keep the radiant heat emitting from the home from hitting the roof. The result is a cooler roof deck, which will reduce ice damming. Many customers have seen a significant reduction in ice damming after installing AtticFoil® radiant barrier. We also also suggest checking to make sure you have good attic ventilation, since cold air entering the attic will also help keep the roof cold.

  40. Hello. I live in northern Arizona, high elevation, high wind area. The 2000sq ft house has a truss roof with 3 gable vents, no soffits. As I add insulation, should I create a 1-2" gap above the exterior walls where soffit vents (normally) go? Or should just get as much insulation as possible above my walls since we are not venting through soffits. Again , high wind area, usually no issue with ventilation since we have a gable vent installed on a windward and leeward side of the house. Mark

    es, you still want gaps at bottom or near bottom between 1st & 2nd run. Hot air will rise to top gable vents, but needs a place to get in bottom area. The gable vents may be intake or exhaust vents depending on the wind. This is good to get air in/out of attic, but you still want air to circulate within attic/behind foil.

  41. Hello, I have a house build in 1920 ,we have a roof replaced and they put a ridge vent on my roof . However I do not have sofit vents, and we just added insulation for the first time the house didn't have much. Do I need gable vents?

    You need some sort of intake vent for sure. Soffits would be my first choice - I know in some areas fire code can conflict with that, but without an intake source, the outtake vent isn't going to function properly.

  42. I'm looking to reduce attic temps in an attic over an unheated/cooled three car garage (located in the Dallas area). There obviously is no insulation in the ceiling of the garage. Would installing a radiant barrier to the underside of the roof sheathing within the attic reduce attic temps sufficiently? TIA

    This is a great application for radiant barrier because in a garage, there is nothing better to temper the heat gain! We’ve seen people get results ranging from 10 degrees cooler to 30 degrees cooler just from adding the foil. Also, since the garage is not conditioned, you don’t really need to have insulation (fiberglass, etc.) in it.

  43. Ed, I live in Phoenix, AZ and need to install a new asphalt shingle roof. My house is concrete 1974 block construction and has 2' exposed roof rafter tails and only 4" frieze blocking, except for 8" blocking at the exterior block wall at the covered patio. The only attic venting consists of two triangular-shaped passive gable vents (probably around 6 SF for each vent). Should I have the roofer install a ridge vent (half of the estimates I've received included it) or is that a waste of time without adequate intake venting? If I was to install install vents, what kind would be most economical and functional? Thanks, Perry Warner

    Thanks for the question. You're thinking about this right - if you don't have much in the way of intake, then an exhaust vent isn't really gonna do much. If all you have is gable vents right now, I'd recommend taking this opportunity to try to get soffit vents installed. Open, properly done, soffit vents will draw in plenty of fresh air that can then flow out of the gables on either end. Open soffits will also "feed" a ridge vent, should you decide to go ahead and add one. No matter what you choose, I'd definitely look at getting the soffits done, it's gonna make the biggest difference of all the options.

  44. My house does not have sofit vents. I have an attic fan, and if I run it how would fresh air come in, and with two small gable vents is that enough to vent the air out?

    Maybe, maybe not. If the fan doesn't have enough air to pull from the attic vents, it will put from the home itself and that could cause the home to go under negative pressure (which, among other things, is a HUGE energy waster). I'd recommend you either get some soffits installed OR disable the fan and let it just act as a passive vent (versus a powered one).

  45. We have 1902, 10/12 pitch house, needs 21 squares and new OSB. We are getting a new roof: one company wants to put the same six box vents, another company wants to only put a ridge vent. No place for soffit vents. What is best?

    There's not necessarily one that's better, but whichever allows for some soffits (or some lower mounted vents) is the way to go. You need a place for air to come IN to the attic. If you don't have that, it doesn't matter what "exhaust" venting you have, the air flow won't happen without intake.

  46. The roofer installed a ridge vent with the new roof in 2004 in my 1933 home which had no overhang eves and no soffits. Since then I have had moisture damaging an upstairs bedroom ceiling which is under the slant of the roof but has a 5 foot high wall creating inaccessible space under the roof. In addition, I also see black areas on the wood in the unfinished attic under lower part of the roof near the attic floor but only on this same side of the roof which faces north...not on south side of roof. I have windows at each end of attic which I open in warmer months. Should I have the ridge vent closed up ?

    I recommend you contact at least 2 different professionals to come and take a look and perform an audit to see where air is leaking from and how to best remedy the moisture problem. I recommend 2 so you can compare their notes and findings to see what the best course of action would be.

  47. I live in the Chicago area in a 1800 sf ranch home that is rather low and is on a concrete slab. It has no soffits but 2 gable vents on two perpendicular sides of the home, plus 4 or 5 turtle vents. The previous owner moved the furnace to the attic, which I already know needs additional insulation. The ducts appear to be well insulated. My problems are these: 1. the house is cold in the winter and hot in the summer (especially noticeable when temps are to the extremes, like the furnace and a/c can't keep up), and 2. I get terrible ice damming. I know I need to seal any leaks, add insulation and get proper ventilation but everyone I've consulted has a different solution, ranging from building a barrier around the furnace, adding soffits to the home (not going to happen), installing an attic fan, adding a ridge vent (but my roof is new), spraying foam insulating the underside of the roof, adding more turtle vents but lower on the roof, all the way to getting electric cables on the roof to melt the ice. What approach (or combination) do you think would help alleviate my problems. I don't know who to listen to or trust anymore.

    Online you can find endless opinions on how to approach this, but it isn't complicated. At the very core you need to have 1) an attic floor that is AIR TIGHT (this means the ceiling is sealed, insulation is at code, and any ducting is checked for leakage and 2) a radiant barrier in the attic to stop the radiant heat from coming in to the attic. For a mixed climate like Chicago with HVAC in the attic, you really want to consider having it stapled up along the bottom of the roof rafters and laid down over existing insulation (that's air tight) in any areas where you have access (ie. no ducts, storage, etc.) Those are the two main things you need to do to cool the home down, stop the ice damming, and make the home's temperature easier to regulate. Check out this great resource for more info:

  48. Hello Ed, I live in southern California in the San Fernando Valley where peak summer it can get easily 100+. I am having a new roof installed soon and I want to be able to get the most optimal attic ventilation. I am going to get a ridge vent installed for the exhaust, and will have low profile Ohagin vent's around the perimeter of the roof for intake. Unfortunately my house does not have the eave's needed to do soffit vents. Three questions I have 1. Will I still get adequate attic ventilation with this setup? 2. As of right now only ventilation I have at all on current setup are two gable vents on the east and west sides of the house, which are located near the peak of the roof. 2. Would you recommend sealing off the gable vents to eliminate cross venting that can mitigate the new vertical venting system I plan to have installed? 3. If I left the gable vents as is what would be the consequences of doing so? The roofer does not do stucco work so he said he won't be able to seal it off so I would have to do it myself.

    O'Hagen vents are typically installed in the upper portion of the roof, so it does not make sense to combine these with a ridge vent. Instead I'd keep your gable vents and add the ridge vent along with some radiant barrier in the attic. It sounds like you're hoping to use ventilation to lower the temps in the attic but that's only going to go a little ways towards helping that issue. A better investment and approach would be to add a radiant barrier that blocks 97% of that radiant heat from getting into the attic (and the home) and then use some passive ventilation to user out the warm air. Check out this video to learn more about why ventilation alone won't solve your problem:

  49. we just had a solar attic fan installed and radiant barrier, the foil type that is staped to the rafters below the plywood. should the solar fan be vented below that foil? in other words should there be a cut out in that radiant barrier foil for the solar fan? also what about the ridge vents? should they be open to below the radiant barrier also?

    The fan should not be obstructed from pulling air out of the attic, so if you have foil below it, blocking it, then you need to cut the foil out around the bottom of the fan so it can work properly.

    Please note we do not recommend ever mixing powered vents (like a solar fan) with passive vents (like a ridge). We've seen this backfire time and time again - the two do not work well together. For more info on why, you can read about it on Myth #3 here:

  50. I live in DFW area. I have one room located on the 2nd floor of house. The majority of the walls and ceiling for this room sit within attic space (part of ceiling is a cathedral ceiling and part of one wall is an exterior wall). It is insulated with fiberglass between studs and ceiling rafters. Is there any value to wrapping the walls that are accessible from attic with AtticFoil? From inside room the layers would be drywall, insulation AtticFoil and the attic space.

    Yep, these knee walls can benefit greatly from having foil added to them! You can see complete install info here:

  51. We just had a new roof put on, they didn't install any roof vents. we have no soffit or eves. Don't we need some type of ventilation? What type of vent would be best for a home with no soffits?

    Maybe - this would be a great question for the roofing company. Perhaps the roof is under ventilated (with battens) so they didn't cut into the decking/attic to vent. It's OK to have a non-vented attic in some situations. I'd start with talking to your roofer to find out if the roof is vented. Then maybe talk to them about adding gable vents to the attic if you want to vent it. Here's a great resource to help you understand more about venting and attic versus not:

  52. We recently bought a home in Oklahoma that has radiant heat in the ceiling. Now that summer has come upon us our house is heating up big time. I have noticed there are no vents in my attic. Can I install them or will it let the heat out of the house in the winter?

    If the radiant heat was done properly, it should be well insulated above it. You can add a radiant barrier ON TOP OF the insulation on the attic floor, and that would probably be your best bet. Adding ventilation to the roof should not affect the radiant heat tubes, again if it's buried under insulation and covered with a foil barrier.

  53. Have a Cape Cod Style house. No Soffit/Eaves venting intakes. Only Gable vents, one each end. Roofer added Ridge Vent. Was this necessary? Or counter productive? Live in Southeastern Pa, close to New Jersey. Thank You

    Gable vents and ridge vents can work together - they're not counter productive per se, but it would have been better to install some soffit or eave venting so you can draw in the air from down low. If possible, I'd still look into getting some intake venting done.

  54. Ed. I live in Denver Colorado so we experience not only hot months, but freezing months. also with being so close to the sun the air gets very hot. is there any disadvantages to doing the staple up method, leaving a skirt slit and ridge slit and then after putting down blown in insulation on the floor of the attic, putting a radiant barrier over the insulation? would the radiant barrier be needed on the floor at all? my main goal is to reduce attic ambering as one of my joists has started to crack and others show signs of micro cracks and i need to reduce the heat of the attic. my secondary is to keep the bedrooms on the second floor warm in the winter. my windows and door company quoted me $22,000 for new reflective barrier with r-15 rating, and new loose fill insulation and sealing all penetrations. they have a discount they offered me but i can not disclose the final price as per an agreement with them. lets say its still in the double thousand digits. I have priced out insulation and your barriers for about $3800 - $5000 depending on insulation. it seems a lot. thanks for any help you can provide.

    Thanks for the questions. First of all, your gut is spot on. That's a LOT of money for a job's materials that cost maybe $500-700. If this is something you can do yourself, or even hire a handyman to help you, you'd be better off.

    As far as the two layers go, yes, based on the info you gave (about your goals in keeping the attic cooler in summer and the bedrooms right below the attic warmer in winter), I think doing a combination of both methods is fine. I'd recommend the Original AtticFoil on the rafters but for the over-insulation, you probably want to go with the SuperPerf that breathes well and was designed specifically for that type of installation:

    In this video I talk about doing both methods and why sometimes I do recommend people go that route:

    Hope that helps!

  55. Hi Ed, I read your great article on why radiant barriers need an airspace to work, and why sandwiching them between roofing felt and asphalt shingles with no airspace in between will not work. My question is: why doesn't the vast amount of air space in the attic, between the radiant barrier and the drywall ceiling, count for this required airspace? Why does the airspace need to be on the exterior side of the barrier, and the air space underneath doesn't matter? Thanks for your time!

    Thank you for your question! It DOES work, that's why products like Techshield and Solarboard (roof decking with radiant barrier attached and facing down, into the attic) work! Aluminum is great because it blocks radiant heat via one of 2 ways: reflectivity or emissivity, so as long as one side of the foil faces air, it will work. Check out the article here this page to see the results of a study the DOE sponsored that shows 3 ways to add radiant barriers to attics and why stapling to the bottom of the rafters (and using the reflectivity property) is actually the MOST effective option:

  56. Hi Ed, We live in Illinois. We got our soffits replaced 2 years ago but recently we noticed that there was no airflow(light in attic) . I am guessing it may be due to the wood not cut properly behind the soffit or the insulation blocking the soffits. We haven’t made any changes to the attic insulation. Is the soffit installation company responsible for making sure that the soffit ventilation was proper while installing new ones?

    Yes, if you suspect that they did not do a complete or correct job, you should contact them.

  57. I have a Florida house built in 1930, no soffits and no room to add them. Currently have a asphalt shingle roof. Considering a metal roof next time roof is replaced. There are only 2 gable vents, one on each side. Attic is super hot in the summer. Wondering if I should install fans in the gable vents? Have to consider hurricanes with any solution.

    I would not recommend installing attic fans until you've FIRST installed a radiant barrier. Passive ventilation will work if it's done right and your attic can be a lot cooler if you staple up a radiant barrier.

  58. I have a gable end wall, North facing, with a vent of approx 12x12 inset, the draught through it is super chilling the entire attic space, can I temporarily seal this during the coldest months. There is no chimney stack and I believe there has never been one.

    If you close off a vent in an attic, you interfere with airflow and air movement (ventilation) is the main way to manage moisture. Moisture that doesn't dry out quickly leads to mold/mildew issues, so I'd caution you against closing off a source of ventilation.

    The attic is not a living space, so there's no issue with it being cold - it's supposed to be cold! A warm attic/roofline can lead to ice damming and other issues. A cold attic shows that plenty of outside air is coming in and keeping things dry and cold, as they should be. It's not likely this is having any affect on the interior of your home, but if you were concerned about the home losing heat to the attic (again - not likely or else the attic probably wouldn't be quite so cold), then you could place an air barrier (AtticFoil works well for this) over your insulation to help make it more energy efficient and comfortable below the attic. Install instructions are on this page:

  59. Hi Ed, I found your blog doing R&D on attic ventilation for my house and found your info to be the most helpful so far. Here is my situation, I live in 100 year house with a slate roof and zero ventilation. Our plan is to replace the roof Spring 2022 with the Grand Manor shingle. My attic is partly finished with two knee walls and a double hung window on one end. The solution provided was keep the window slightly opened all year, cut a 24x24 opening in the finished ceiling so it can escape out of three new mushroom vents installed on one side of the roof. I'm lost if this is even a solution. Any help would be greatly appreciated. Thank you- Jason

    I would look for a product called "Roof Edge Vent". it can be installed on the drip edge and a slot cut in the roof. This will allow air to come IN. Then, you will need some way OUT - the "mushroom" vents should work.

  60. My house always gets warmer during the day and has a hard time cooling during the day. So I have a few projects I’m looking to do so my questions would be would it be better to add both a radiant barrier and an attic fan to my attic? Does it work well for helping keep my home cool in the summer and warm in the winter? The heat from the attic seems to be the big culprit here. Just looking for a little insight thanks.

    I would start with just the radiant barrier and see how it goes from there. You may not need more ventilation and even if you do, attic fans are not my first choice. This page on the AtticFoil site explains how much cooler you can expect the attic space to get after a staple-up installation:

  61. Hi Ed, I came across your page looking for attic ventilation advice as I'm getting ready to redo my roof. Your site is much more informative than others I've come across. My situation is the following, my home has a low pitched roof with a ridge vent and gable vents with no soffits. Is this the best setup for my situation or should I make some modifications? Any help is appreciated!

    This page gives the best options for venting an attic space:

    Even without soffit venting, it is important to provide an air gap at the soffit level to help keep the roof deck dry. For more information on ventilation and moisture control, read that article I linked above. As a general rule of thumb, I think you should use soffit vents as your intake source for attic ventilation. In cases where it's simply impossible to do, the next best options are laid out on this page: How To Vent an Attic Without Soffit Vents:

  62. I just had my roof replaced. An attic fan was used for ventilation. I previously had a gable fan. I am concerned about enough intake. My house did not have ventilated soffits when it was built in 1971. When siding was put on contracted drilled holes in spots . However, insulation covers the soffits. Are gable vents enough intake or should I get someone to cut the insulation back?

    The gable vents *may* be enough, but even if they are, they don't really create that full ventilation loop in the attic. That's where air comes in low, heats and rises, and vents out up high. I'd still recommend getting those soffits cleared and opened up for the best results.

  63. I have a interesting issue. I recently bought a house in west Iowa. I had an Inspection done and all was okay except the report said there was not enough insulation compared with modern codes. I expected that since it was an older house. The house has a roof that is two years old. Fast forward to me actually looking to put more insulation in the house a year later... I am facepalming myself. I have a serious problem. The upstairs areas have a partial cathedral ceiling for walls and attic for ceiling. This means my roof looks like a capital letter A. Half walls Half attic. Using my thermal camera I can see that the cathedral part is insulated most well. Just a few small spots with out insulation. All insulation is cellulose fill. Upon looking in the attic I have confirmed that they have filled the entire cathedral cavities with cellulose and there is not any soffits or air space to add soffits. The attic portion of the roof has ridge vents with a single gable vent. The gable vent is of course intaking air instead of exhausting, which is a no no. I can see that the cellulose insulation around the gable vent area has blown away in a V pattern leaving no insulation in that area. I am in a high wind area. I do not know what to do. Hence my face palm. I can not add soffits without redoing a two year old roof or tearing out interior walls... I can not close the gable vent, because there would be no feed of air for the ridge vent. I am sure there is some rain/snow coming in the gable vent when there is high winds. I am thinking I am getting some siphoning effect as well. This attic space is 12 x 24ft and 5ft high at the peak. It is unused space. The one gable vent is about 18x18 in and centered, so about 2.5ft up from the floor of the attic. The temperatures range from -20f to 100f. We had snow and 85f temps this week! The house has a single roof.. Here is what I am thinking and looking for better ideas or solutions... I am thinking to OPEN cell spray foam the attic area floor to airseal the attic portion of the roof. Add some fiberglass batt to add the remaining R-Value I desire, add a 45 degree deflector up to keep most of the rain/snow mix from getting in and allow the water to drain back out the vent, and finally add radiant barrier foil all the way from the ridge vent down to and above 6in from the final insulation at the bottom. This would create a soffit effect and force the higher gable vent air down and maybe more evenly through the attic. Then the air would travel up behind the radiant foil to the ridge vents. Does this sound like a good idea at all? What would you suggest? I am at a loss of what to do and maybe just over thinking it all. Thank you for your advice.

    Yeah, that is a lot going on but I think your plan is sound and considering all you have to consider, I think you're on the right track. Start with the spray foam, then do the foil and your vent diverter, and then finish up with your loose-fill insulation last (so you're not walking all over it and compressing it (or worse - aerating the fiberglass!). Best of luck to you.

  64. If I have radiant barriers in my attic which are working well since the attic temp is no more than 10 degrees more than the ambiant temp outside, however, I am getting a new roof installed. This installer usually includes ridge vents. I currently have a power fan along with my radiant barrier. If he took out the power fan, is adding ridge vents counterproductive in combination with the radiant barrier? Or would it be ok, replacing the power fan with the ridge vents which would cover all three attics. (the power fan only covers largest of the three attics)

    I see no concerns with changing your powered exhaust to a passive exhaust but I do caution against MIXING the two (active and passive) in the same space. You still want to have the foil cut out near the ridge (if you followed our instructional page on how to install, you should be good to go) and then I'd just go all ridge vent and make sure your soffits aren't blocked so they can feed the ridge vents.

  65. Hello, Ed. I have read through many of the inquiries on your websites, all of which are an incredible resource for homeowners looking for answers. I still would like to field my personal house situation with you to help with a coming roofing ventilation and possible radiant barrier over blown insulation decision. This is long. That’s because I don’t know enough to figure out what to omit in terms of layout and background. Please bear with me... LAYOUT: I have a 1232 sq ft, 1939-built, single story conventional home in eastern Virginia. No eaves at roof line except a small area, noted below in description. Temperate, close to coastal region known for wide daily temp variations and high summer humidity. Front of house is direct southern exposure, with a covered porch that I do not believe opens to the attic, but I am not certain. Current ventilation comes from two rectangular gable vents (do not have measurements) positioned at peaks of two gables of house: one on the southern exposure front and one on the east side of the house. Two turbines are spaced across the "main roof" toward the ridge on the northern exposure side. There is one area at the back of the house where about 7-8 linear feet of soffit vents (not in a straight stretch) were retrofitted near a roof valley, along with a water damage repair. That roof region joins the main portion of the house that sits on a crawl space with a four-steps-lower, slab level laundry room and additional bedroom. As far as insulation, there is blown in the main living area; not sure about the slab area attic. Not confident about quality of the job, but some is there. The on-slab portion of the attic is open to the main attic, though only with a substantial body-sized crawl through. This arrangement has been in place and functioned for at least 25 years, with no known damage in terms of insects, moisture, mold, rodents. I do not have temp readings of the attic, so I do not know if I have reasonable readings, or if I am overpaying for my heating and cooling with living space air sucked into the attic. All AC venting in attic is intact and in excellent condition. I never heard of "radiant barriers" until I found your site. Though I have relatively economical heating and cooling bills, if it can prolong roof life and help with heat transfer from the attic in the slab sections of the house particularly, it would be worth a consideration. BACKGROUND AND ROOFING PROPOSALS: Current roof is 25+ years old. I have received quotes for a replacement, and the proposed ventilation options vary significantly between the two companies. One company suggests: 1. Light colored (white "Energy Star" roof shingles) 2. Replace turbines with new ones 3. Keep gable vents open (What is the inflow here, other than the small area of soffits? Are the gable vents “dual duty”?) OR 1. Install DCI "SmartVents" around perimeter of house. I am curious as to what you think of or know about these. No one is suggesting installation of soffit vents if it is even doable in areas of the roof other than where it was done by the architect. 2. Remove turbines and install ridge vent 3. Board closed/block the gable vents with plywood Second company suggests: 1. Remove turbines and install a ridge vent 2. Leave gable vents open and small area of soffits unobstructed (Again, what is the inflow in this arrangement?) MY QUESTIONS FOR YOU: 1. Do that I need SOMETHING as far as vents added down at that west slab end roofing to try to avoid future issues? A portion of any ridge vent installed would extend to that area, but currently there is no inflow venting. 2. Do you favor either of the above scenarios proposed by the roofing companies? 3. If not, what suggestions do you propose I look for with the new roof/attic ventilation? 4. Do you suggest a radiant barrier through all sections of the attic? Thank you for tolerating this! I value input from someone knowledgeable who is not making a direct profit off what I decide! Kaz

    1. If you have exhaust venting, it has to be fed. So yes, you need some intake air to feed any exhaust vents you have (or get).
    2. I don't favor one over the other necessarily - think of it this way, "if it ain't broke, don't fix it." You said yourself that the ventilation seems to be fine as is. I'd recommend measuring the air temps inside the attic now to see where you're at. "Energy Star" roof shingles still get hot - so in either scenario, radiant barrier will make the biggest difference over all other suggestions.
    3. Add radiant barrier to the bottom of your rafters, have plenty of soffit intake and measure the air temp before you install the foil and then after. If AFTER the foil install you're still at least 12 degrees ABOVE ambient temp, you need better/more ventilation.
    4. Yes, cover as much as you can. The more you cover, the better your overall results.

  66. Hello, I have a scissor truss application in a great room and am installing radiant barrier. The radiant barrier is directly on the 2 x 6 roof truss that the roof sheathing is nailed too and an air gap is maintained. The insulation is under the radiant barrier against the bottom scissor truss up against where the sheet rock goes. My question is where the scissor truss meets the eve the insulation and the radiant barrier come together, does there need to be an air gap between the radiant barrier and the insulation where they meet at the eve near the intersection of the scissor truss?

    Yes, I would recommend about a 3" gap at the top of the insulation line before the foil starts. More info here:

  67. we have a house with a pitched roof with gable vents at each end of the house. The vents are above the ceiling height of the three rooms on the upper level. We have no soffit vents. The square footage of the three rooms totals approximately 550 sq ft. the space above the three rooms is about 4 to 5 ft AT TOP OF THE PEAK. WILL AN ROOF MOUNTED FAN THAT DISPERSES 1000CFM WORK AND REUCE THE TEMPERATURE IN THOSE THREE ROOMS?

    No, not really. The air temp in that space is definitely super hot, but the rooms are hot because of the RADIANT heat being absorbed into the insulation/room ceilings. I always use the car analogy: Think about a car parked in the sun & a car parked in the shade. In both scenarios (car parked in the sun and car parked in the shade), the outside *air* temperature is the *same* whether the car is in the shade or the sun. But we all know getting into a car that's been baking in the sun is SO MUCH hotter than a car that has been in a parking garage, even on a hot day. So what's the difference if the air temps are the same? The difference is the car in the sun is absorbing the sun's radiant heat and the car in the parking garage is not!
    Now think of your home that is heating up - it's in sunlight most, if not all, of the day! Just like the car, it's going to heat up - and at some point in the day it's going to become hotter inside the house than it even is outside the home! We know that shade would help solve the problem, but outside of moving your house or planting a bunch of trees, how can you do this? Well, it's pretty simple - use radiant barrier! A radiant barrier will reflect the radiant heat away from the upper rooms. The foil layer will REFLECT 97% of radiant heat that hits it; the effect is just like putting the building in the shade (or like having a really cloudy day). Check out the Original AtticFoil here: to learn more about radiant barrier and how to install it.

  68. Hi Ed, we live in Ky and have a small ranch with a courtyard in the middle. Our rood has no ventilation soffits and not enough roof vents. We have a pull down stairway from the garage where my husband installed a large fan to suck the warm out out. That fan only gets to one side of the attic due to the courtyard space in the middle of the roof. Our house pops and cracks excessively in hot weather and the attic temp is 150 degrees plus!! (guessing, maybe hotter) What should we do to cool down the attic? We have no way to install soffit vents!

    You should install a radiant barrier! You don't need ventilation in order for the foil to work - just an air gap. Staple it to the bottom of the rafters and follow the install instructions here:

    Ventilation is great and helps lower air temps but you also have a lot to gain by blocking the heat before it ever gets in the attic space to heat the air up. I think you'll be pretty impressed with how well the foil does, even with minimal ventilation.

  69. I live in southeast North Carolina. I have a 1960s house that I have installed a brand new roof on to include a ridge vent. I have two feet of soffit space running around the house with soffit vents. The roof is a hip roof design. The house is approximately 1000 sq/ft. I want to install mineral wool insulation on my rafters and leave a one and a half inch air gap between the mineral wool and the roof sheeting to allow air to flow from the soffits to the ridge vent. The purpose of this is to reduce the amount of radiant heat into my attic as well as prevent the heat from transferring to my ductwork that's going to be installed in the Attic. My Hope is that the mineral wool insulation will allow my attic space to become somewhat conditioned without the excessive heat loss or heat gain. What is your thought?

    My thoughts are that 1) there's a better place to add more r-value to your attic (if needed) and 2) a radiant barrier will do a much better job of accomplishing what you're after than mineral wool. R-value products, like mineral wool, should go right up against the thermal envelope, that is, the space that's being heated/cooled. In most cases, that's on the attic floor, covering the space right above your living space (inside of the house). Radiant barrier is going to be most effective up on the bottom of rafters, alone, with the rafter cavity providing the necessary air gap and the air coming in the soffits being able to either enter the main attic space or travel up between the foil and the roof deck, venting out your ridge. The full install page is shown here:

  70. I am south of Indianapolis. I bought and gutted a 1901 Victorian style house. The HVAC has just been installed and runs through where the chimney was (I removed it). They ran insulated ducts through the attic to ceiling vents in the bedrooms. The layout is odd: the main square of the house has a high attic (above the 2nd floor), where all four sides of the roof meet in a single peak, like a pyramid. There is no venting I. This section. The chimney used to go through the peak before I removed it. But one area of the house is connected to the main square, and its roof comes together with just two sides and has vents on the ridge. Obviously this section would be an easy install for a foil radiant barrier and, from what I have read so far, would have no potential issues getting air to flow from Soffits to vents. My question is about the main square. Does it make any sense to run a radiant barrier from Soffits to the peak? Should I install an attic fan to redirect the hot air back down to the section with ridge vents? Or is it even feasible to install ridge vents on the main roof?

    Yes, you should still get a radiant barrier under the roof where you can. You don't need to have vented air for a radiant barrier to work - it's helpful for keeping the air temp in the attic down and for keeping things dry, but the foil doesn't require ventilation. As long as you have a ½" air gap or more on one side of the foil (this easily occurs when you staple foil up on the rafters), the foil can reflect back radiant heat from where it comes from. So even if you can't vent that area, you can still benefit from a radiant barrier.

  71. My home attic was insulated by a company that contracted with the state energy assistance program. They did a home energy assessment, air sealed, and insulated the attic. The second floor of my home is a rectangular structure built within the triangular roof area to about the upper third of the roof. The lower part to that point is insulated against the rafters with blown in celluloids. The area above the ceiling of the second floor has several feet of blown in fiberglass insulation. The upper third of the attic is not otherwise insulated. Shortly after this was done I experienced frost and moisture in the attic with occasional drips coming through the ceiling/wall where it meets the roof line on the second floor. The company came and vented the roof with four static vents. This didn't solve the issue completely. I've had roofing and another insulation company out and none could offer any advice. I'm afraid this ongoing cycle of dampness will eventually ruin my roof which is less than a decade old not to.mention my rafters. Images are here:

    Yeah, I'm not sure what the issue is - it would be impossible for me to guess without seeing the space for myself in person. Moisture is pretty predictable though. I'd recommend reading this article about moisture's causes:

  72. Ed, My 1970 home is in north central Minnesota. It was built by a man from Norway and is an unusual home for our area. The entire second floor is a cantilevered overhang. It is constructed with four large gables (one in each direction) and there is a gable vent in each one. (Well, the builder cut 4 triangles and covered with screen like a vent.) The attic currently has blown cellulose insulation, but it has compacted and is not adequate so I am planning to replace it this year. There are no soffit vents since that area is floor space for the 2nd floor. (I suspect there is inadequate insulation in the soffits and I plan to have that corrected this year. ) My main problem this winter has been ice dams on each of the four valleys. My late husband purchased baffles, but they did not get installed before his death. I know he intended to improve attic insulation since I recently found a "to do" list with that notation-- but I don't know what kind. The climate here rarely gets over 100 degrees with the warmest summer days in the 90s. Winter is a different story with below zero temps common. The poor attic insulation combined with a heavy snowfall this year has caused those dams, I'm sure. Also- I think there is a ridge vent in the attic since I noticed melting snow on that area right along the roof peak. Our climate gets humid in summer with all the nearby lakes, but I don't see any mold or moisture issues in the attic. My questions: Should I add the actual gable vents to each dormer (vs the screen over a cut opening)? Do I need interior baffles if I do not have soffit vents or a low vent on the roof? (I just got my roof shingles replaced last year.) Is there a type of insulation you would recommend for the attic (cellulose, foam, etc) ? Can all types of insulation be used with the addition of a radiant barrier like your products? Do you recommend insulating the attic ceiling (underside of the roof) as well as the attic floor? I am hoping to update my windows and siding this year, so if I should add an additional kind of vent now would be the time. Any other advice? My husband made these kinds of decisions before, but I appreciate your website which I found today so I can educate myself on what should be done to eliminate problems in my home. Not a lot of local contractors seem to be familiar with our unusual construction. Thank you.

    The main reason ice dams happen is actually because of air leaking out of your warm home, into the attic and hitting the underside of the roof deck. The sun hitting the roof would melt the top of the snow, not the bottom of it. The reason ice dams happen is because the roof itself gets warms and melts the bottom layer of snow but because it’s freezing cold out, the water re-freezes and forms the icicles. So the main goal is keeping the underside of the roof COLD and fixing any leaks on the attic floor. More info here:

    Then, after you’ve checked for air leaks and done the work to seal them up, you can lay SuperPerf AtticFoil over your existing attic insulation on the floor to help stop winter heat loss and *bonus* it will also keep heat out of your insulation (and home) in the summer time too!

    If you do those two things alone - seal the house for air leaks and install a radiant barrier on the floor over the insulation, you will most likely find you don't need to mess with all that other stuff. Remember, the GOAL is to keep the roof COLD in the winter, so it can't melt the snow and then re-freeze (causing the dams). Doing both of the above will minimize/eliminate the warm air from hitting the roof and warming it up so you should solve the problem. Wishing you the best!

  73. My home is a spanish style home built in 1900. It’s 3600 sq ft. My electric bills are astronomical. I’ve been studying my attic. I have a knee wall attic that goes around the top floor. I have discovered that someone who live here before plugged all the soffit ventilation with insulation blankets. I’m in the process of digging those out, but I do not see anywhere for the air to go. There is an upper attic with 1 big turbine like vent but it has no intakes. I’m thinking of using the radiant barrier in both knee wall and upper attic but should I also devise a way to have the air from the knee wall come into the upper? It would probably be from creating a chase in the room below the upper attic into the knee wall attic. Plus the knee wall attic is filled with ductwork. Any suggestions are appreciated as it’s a bit of a mess in my opinion.

    Ventilation does help exhaust out hot air, but ventilation alone won't solve the problem of a hot house. You've gotta drop the surface temperatures of the items inside the attic, namely the insulation:

    I'd recommend getting AtticFoil on the knee walls:
    And also below the roofline wherever else you can via the staple up method:

    Then, measure the air temp and see if it's within 10 degrees of outside air temp below the foil inside the attic space. If not, then you will need to start seeing what options you have for adding more ventilation. You may find you don't need to add anything, or you may find that opening the soffits is enough.

  74. Mr. Guru, The 30x32 pole barn on my recently purchased property has no soffits, nor a ridge vent, or even a gable vent for some odd reason. There is a moisture barrier between the metal roof and trusses, but that’s it. I installed an electric roof vent fan that has a humidity/temperature trigger on it and it moves a good amount of air, but I’m wanting to install a bar and TV, etc., for a nice hang-out space. The walls are not insulated or covered (yet) nor is there a ceiling, just open truss space. My question is, if I install properly sized gable vents (which I will do regardless), will that be enough to ventilate the building properly with enclosed walls and a 10 foot ceiling, or is more venting needed?

    If you're wanting to make it cooler inside there to enjoy as a hangout area, ventilation isn't your main priority (it's good, but not gonna make the biggest impact). Sounds like you need a radiant barrier to reduce the heat load and then your fan can pull out any residual heat inside on stuffy/humid days. Take a look at for metal building insulation - I think the Pro 2mm product would probably be your best option.

  75. Hi Guru, I have a 1963 Cape, it has a cathedral ceiling and no way to access from within. When I purchased in 2020 they had put on new siding, covered old gable vents and put a new roof within last 8 years with ridge vents and no soffits. Now I’m faced with flashing issues and other minor repairs and I’m wondering if just ripping off this roof and replacing and adding soffits ? Or just reopening the original gables? My friend who is an architect called this a closed system and said they shouldn’t have closed the gables. Please please need help!

    If you already have the ridge vent installed (properly), I'd recommend adding some intake vents in the form of soffit/eave vents. This will allow cooler air to enter the cavities and as it heats up, make its way to the ridge to exhaust.

  76. I’m half thru with my radiant barrier installation. I’ve got ridge vent and 2 exhaust fans midway up the roof pitch. Should I cover the area where these fans are during my barrier rollout to create a suction of sorts or leave that rafter open around the exhaust fan. Thx for any input in advance.

    You never want to block off the areas under vents/fans because they need to pull air from the main attic too. You leave these areas open or cut out around them - more info on the install page here:

  77. My attic ceiling is insulated with cellulose, the house has soffit vents in the overhang all around the house. There is no ridge vent or gable vents. As far as I can tell there is no exhaust venting, so input from the soffits is probably restricted. Also, there are no baffles in the ceiling rafters. What can I do to get proper ventilation to reduce heat and moisture build up during the summer?

    Check out my article on How To Vent an Attic Without Soffit Vents:

  78. I have a roof with a 6 inch overhang vented soffit on one side. I can’t vent the other. There is one gable vent I can’t vent the other side. There is R38 roll insul with baffels in. I put on a new roof and added a ridge vent. It is condensating like you wouldn’t believe. What can i do?

    Condensation happens when relatively warm moist air comes into contact with a colder surface. So somewhere you have warm moist air "leaking" to get to the cold surface of the roof deck. You need to find the leak and seal it up.

  79. I live in North Texas. New metal white roof. House built in the mid 70’s. No ridge vent and no exhaust vents on roof itself if that makes sense. It has gable vents on north and south side. It also has soffit vents. I installed radiant barrier and more insulation (didn’t have enough) in the attic as instructed almost 2 years ago. It’s still hot up there. I’m thinking of installing an attic fan in one of the gables. Would this be ok? And should install be on the north or south side? TIA Patricia Blackwell

    Patricia - I do not recommend attic fans and I get into the details of that in this video:

  80. Hi Ed, We live in Costa Rica - warm climate year round, near the beach at about 1400ft altitude. Windows/doors are always open, mosquito netting. However, air kind of comes in on one side of the rooms, and does not have a way to escape other than (one gable vent - not two...) We have powerful fans, which create additional airflow. The older part of the home has asphalt shingles, and the construction company did not provide for insulation neither ventilation nor any soffit. Some rooms have issues with airflow (hot air gets stuck in the top of the roof (high ceiling, ceiling = the other side of the roof). As the windows/doors are always open, would/could this then effectively works as intake for a potential ridge vent (not yet installed, but we are considering it?).

    If it's about moving air, yes you can use the open windows and doors to draw air in lower and as it heats up it can rise and exhaust out a ridge style vent. It sounds like heat is also a concern, so I would consider installing a radiant barrier too. As I mention in the following video, moving air won't necessarily cool things down - at least not completely:

  81. I have spray foam off gassing in the attic and coming into the house. Would adding an attic fan help to draw the off gassing out of attic?

    Maybe, but the added risk of adding a fan that doesn't have enough intake isn't worth it in my opinion. More info on why I don't recommend attic fans here:

  82. Wow what a great website so much information! We have a 1920s home with a flat roof and we would like to do something to cool it down in the summer. We have no AC which we don’t need here in Ventura it only get hot in August and September. Our square footage is 888. We have 5 vents in the attic already. We are getting new insulation and possibly an attic fan. Would an attic fan be too much since we already have the 5 vents and it is such a small space, would it cause an airflow problem? As far as the radiant barrier goes, it would be very hard to put install because of the flat roof. There is about 24” of head space. I am hoping that you can help us with our decision…fan or no fan?!! Thank you Kelli

    Kelli - NO FAN! You already have so many passive vents - this is not a good idea. More details on WHY here:

  83. I live in Fort Myers Florida. Home has vents in eaves but no ridge vents. 14 inches of insulation between attic and living space. Roof is concrete tiles so the attic does not get crazy hot but starting to see signs of mold on bottom side of roof plywood due to stagnete air in attic. Planning on adding a 8 inch duct fan to get air movement. Is it better to suck hot air from the ridge or blow fresh air from outside to the ridge?

    Air INTAKE needs to come in from down low in the attic and EXHAUST up higher in the roof. So you want to push air into the attic and let it warm, rise, and vent out the ridge.

  84. Let me know if i have a flaw in my approach to better ventilate my attic. My house is ranch style, and the roof has 2 gables that extend out the rear of the house on each end of the house. I'm planning to replace soffits with new ventilated soffit. It has a ridge style vent at the top. Next, and this is where I'm trying to go the extra mile, (Keep in mind I'm in South Carolina) I was planning to install fans vertically on each gable end, with one exhausting, and the other intaking. My thought was to keep air flowing from one end of the attic to the other end. Your thoughts?

    No! No, no, no - don't mix active venting (fans) with passive venting (gable and ridge venting) - BAD IDEA! Check out my short video where I explain why I don't recommend attic fans:

  85. We have adequate insulation, gable end vents, and several added roof vents, no soffit venting possible. Energy audit says we need more ventilation! What to do?

    It depends what you're trying to do. If you're trying to just save energy, ventilation alone isn't going to solve energy usage problems. I discuss this more here:

    If you're trying to conserve energy, you should consider a radiant barrier which will reduce the amount of heat coming into the attic in the first place - that makes a HUGE difference! Then, you may need to add some lower vents to the roof, like I discuss here:

  86. Hello Ed, I live in a condo complex built in the 90's, ranch style with cathedral ceilings. All the condos had new roofs installed due to weather damage. We had gable vents with roof vents, no soffits. They took out the roof vents and added ridge vents. Will this be enough air flow? We all have attic access doors and skylights. Live in Michigan

    It might. The best way to know if you're getting enough air flow is to 1) inspect the area for condensation and 2) use a probe thermometer to measure the air temperature in the attic space. I made this video a few years back talking about ventilation and air flow that may help too:

    Another good article to consider is this one:

  87. How to install radiant barrier on roof with gable vents, no ridge or soffits?

    The same way you install it on a roof with gable vents and a ridge vent - there's no difference!

  88. I recently bought a home that was built back in the 1940's. I don't have the exact year but definitely in that range. It has a hip roof with a dormer on the front. No soffits that i can see nor any ridge venting. I suspect the attic insulation may be from that same era, paper backing and breaks apart easily. During the summer months the attic temp gets to 110 to 125 degrees (95 degree day). I have ceiling fans on the main floor but the ceiling temps run from 78 to 87 degrees depending on the time of day so the AC runs all day. My question is what's best in this scenario? Insulation is my first thought because it's needed regardless. I was considering a temp controlled attic fan but the concern is will it possibly pull the conditioned air out too during extended heat waves (using the dormer windows as an exhaust for the hot air). Considering also insulating the roof rafters to reduce the heat from the exterior roof transferring to the attic interior. Not crazy about the idea of altering the roof but will leave that to the professionals if needed. The other thing is the attic floor "bays" range from 13" to 16" inches in width. Same for the rafter bays. They run 13" to 24" inches in width but all are 5.5" inches deep. Overall attic floor is 34' by 27' feet. Thanks in advance for the help...

    Pretty straightforward - you need a radiant barrier stapled to the bottom of the roof rafters to start. Don't neglect to leave the proper air gaps in the foil install so your roof can still vent as it does now. A fan won't change the fact that you have heat coming in, it will just blow the air around - but it's not the hot air that keeps your upper home hot, it's the radiant heat that absorbs into the home. Take a look at this installation page:

2 thoughts on “Attic Ventilation

  1. We have lots of heat coming through the attic floor. The floor is insulated and floorboards are over top. Is it possible to use a radiant barrier on top of the floor boards? Very very seldom does someone go into this attic space, but will the radiant barrier rip or be injured if we would walk on it? What do you say about the idea that it is not good to put radiant barrier on the floor due to dust?

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