Ask The Guru: Radiant Barrier


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  1. Rating: -1

    Positive Negative

    I live in Michigan and want to use Radiant Barrier in my attic. I want to staple to the bottom of the roof rafters. I am going to leave 3 inch space on the bottom and three inches on top. I like to use non-perforated barrier, I think it does a better job. Since both sides will be ventilated and the same temperature, do I have to worry about condensation, or can I use it?

    The perforated and non-perforated (solid) radiant barriers work exactly the same. The holes are tiny pinholes about 1/2″ apart. The difference in effectiveness of the two products – (reflectivity and emissivity) is so small it’s not even measurable. Vapor barrier radiant barriers should be used with caution regardless of location. The general theory is that you NEVER use a vapor barrier unless you are SPECIFICALLY trying to stop/trap moisture in it’s vapor form. In an attic, you WANT air and moisture to flow freely to maximize the drying process. Therefore, it is NEVER suggested to use a vapor barrier in a vented attic application. If the effectiveness is the same, why risk introducing something that can slow/stop moisture flow out of the attic?
    Also, you CAN get condensation on ANY surface if the temperature is below dew-point and you have a source of warm-moist air. Ventilation helps, but you REALLY want to eliminate the source of warm-moist air.

  2. Rating: +0

    Positive Negative

    I am planning to install your Radiant Barrier over the winter. Almost everything that I need to know has been readily available on your site. I just have 1 question. Is there any diference in running the Radiant Barrier up and down the rafters instead of across. Due to the number of interferences in my attic, going up and down would be an easier install versus going across. Thanks in advance for the information.

    It does not matter which way the AtticFoil Brand Radiant Barrier is run. Generally, it's easier IF you can go horizontal, but some attics it works best to run up and down. If you need a smaller width roll - just use a power saw (miter type or table) to cut the whole roll. You can easily make 3 x 16" or 2 x 24" rolls.

  3. Rating: +0

    Positive Negative

    I covered the underside of the roof starting 3 feet from the soffit and ending about 6-8 inches from the roof vent apex. Is it enough to get a good benefit from the radiant barrier? In your figures you show the barrier starting at the vent. Will the air from the soffit not be able to get behind the radiant barrier and carry the heat away if the barrier is not low enough? Thanks for any help.

    You are fine. Air will naturally find it's way to the top of the attic whether it's behind, or in front of, the radiant barrier AtticFoil. Starting 3 feet up is not ideal, but radiant barrier has a cumulative effect. The more of the roof you cover the more benefit you get - just like shade. If it's not too difficult, I'd try to cover as much as possible.

  4. Rating: +1

    Positive Negative

    I live in the Washington, DC metro area and want to increase the insulation in my attic. I received an estimate from a company to add additional cellulose insulation in my attic and then add a radiant perforated barrier on top. Does any space have to be left between the cellulose insulation and the radiant barrier? Thanks for your help.

    You can lay AtticFoil directly on top of the cellulose insulation.  The required airspace will be on top of the foil.  I would not "mash' the foil down into the cellulose insulation.  Gently lay on top and try to maintain minimal contact if possible.

    For more help, check out these customer submitted DIY photos of radiant barrier installed over insulation.

  5. Rating: +0

    Positive Negative

    An HVAC guy told me that radient barriers will change the dynamics of a balanced system. My system is poorly designed so that The MBR upstairs gets very little airflow and is either too hot or cold. I have an 11 year old, 2800 sq. ft. 2 story home with one zone. He states that by over insulating or otherwise dramatically altering the temp. control demands of your system you may end up with mold or continuously cycling of the a/c unit since it is designed to work at particular specs. In essence you may end up with a unit that is too big for its needs. I cannot afford to have the ductwork redone properly. I'm interested in your response. Thank you.

    Thanks for the comment. The fact is that MOST air conditioning systems are oversized. In fact, we tend to size our AC systems to handle "full load" (which is usually the hottest day of the summer); however, we are usually only at full load" about 2% of the time. So, in reality, most systems are oversized 98% of the time.

    Normally, this is not a huge issue. However, anything you do to drop the load more (including installing radiant barrier) can cause most systems to be even MORE oversized (the difference between what it can do and what you need it to do becomes a big difference), which could result in a lack of dehumidification but this really depends on you climate area. If your air conditioner is "short cycling" then you have a couple of options. The easiest method is to install a dehumidifier to pull out extra moisture. Or, you can install a two stage (high & low capacity) air conditioner. Personally, I like to use air conditioners that use "inverter" systems. These systems are made by companies like: Mitsubishi, Daikin, LG, Sanyo, Fujitsu and many more. Inverter type air conditioners are similar to a cruise control on a car. The adjust the flow of refrigerant based on the "load." An inverter system will run longer but pull less amps resulting in more dehumidification, lower energy bills and less of a "muggy" feeling in the home.

    For you particular situation, I would install a radiant barrier. Then, if the humidity is too high, install a plug in dehumidifier.

  6. Rating: +0

    Positive Negative

    We plan to install foil radiant barrier in our attic. As I understand it, it is better to install the foil beneath the rafters rather than between them, right? And running it horizontal would make it easier to install. Would outside AND inside radiant barrier treatment help, or not? We could paint the roof (dark asphalt in Texas sun) with radiant barrier paint (reflective to 95%) after we install the foil radiant barrier in the attic. Would this help?

    Yes, you want to install the foil across the bottoms of the rafters so you can eliminate the thermal bypass that would occur if the ends were not covered.

    And yes, you could paint the roof if you don't mind the color of the radiant barrier paint. There are actually reflective coatings specifically designed for roof applications. As far as doubling up the barrier though (on the roof and in the attic) it would only really help if there was a large portion of the attic you could not get to. Otherwise the foil is blocking 97% of the radiant heat on it's own, plus the cost is substantially less than the reflective coatings, so you're better off going that route if you have to choose one.

  7. Rating: +0

    Positive Negative

    I live in a top floor condo in Dallas that was built in 1974. I would really love to install a radiant barrier. I don't have an attic or even a crawl space. I think the only two options I have are: 1. take down the drywall staple the attic foil then replace drywall ceiling or 2. furring strips over the existing ceiling to create the air gap I need and attach new sheetrock. So basically drop my ceiling by an inch. Will this second option work since the radiant barrier will be below the insulation above the original sheet rock ceiling?

    Yes, we have had cases where customers did an install similar to this (attaching wooden strips over the existing drywall, stapling foil to the wood and then adding a new layer of drywall over it). However, the foil really needs to be closest to the outside in order for you to see a real benefit from it as a summertime heat blocker. If there is NO insulation in that ceiling (which is unlikely), then you could get a benefit from the foil, even though the drywall is there. However, if there IS insulation up there between the rafters, then I hate to say it, but without removing the assembly and adding the radiant barrier closest to the roof, you aren't gonna get the great results you are probably hoping for.

    In that case (having insulation above your ceiling between the ceiling and the roof deck), your best bet is to bulk up what existing insulation you have. I recommend you get 3/4" to 1.5" foam board and apply it directly over the existing ceiling and the drywall over the foam board. The only way I'd recommend you using a radiant barrier is if you were going to do the cathedral ceiling install method and you were able to get the foil up against the roof so your results would be worth your time, money and energy.

  8. Rating: +0

    Positive Negative

    Dear Guru, I have a question concerning Radiant Barriers. I have looked for any similar inquiries elsewhere and so far have not found any so I decided to ask you. I am looking into installing a radiant barrier in my existing house (built 2006 but I acquired only last year). I planned on doing the Foil type attached to my rafters possibly next spring when it is not so hot. I was also planning on decking over top of all my insulation for two reasons: (1) to improve ease of installing the foil radiant barrier later, and (2) to increase my R-value (I realize if I collapse the insulation the R-value goes down which I won’t do, but an extra layer of wood should add R-value and also allow the insulation to better perform to its potential by making the insulation layer “Dead air” so it does not transfer heat as easily.) I was going to lay 2x4’s down first in order to have an air gap between the blown in insulation and the decking. My projected cost for this decking was already a few hundred for OSB but I had another thought. I have heard that some people have tried radiant foil on top of their insulation and also attached to the rafters in the same house (doubling up) with pretty good results. Since I am decking I did not want to deal with loose foil under the OSB so I thought I could use OSB Techshield face down (only costs a little more than plain OSB). This also allows me to affect my energy bill this summer since I could budget in the decking this month instead of waiting till next spring (More Savings = Happy Homeowner). From my limited knowledge/experience in this area I just want to make sure I was thinking about it correctly. Techshield as a roof sheathing is face down with the attic side being the air gap, so I should be able to lay it face down (walking on OSB side so the foil backing isn’t damaged) with an air gap maintained by using 2x4’s as spacers. My total cost increase for switching to Techshield is minimal but the potential energy savings would make it worth it. I guess it all boils down into two questions. 1 Will decking (plain OSB/plywood) my entire attic improve my R-value as I suspect? 2 If decking does improve my R-value (or at least does not reduce it) will Techshield perform as a good radiant barrier in that placement? Thank you very much for your time. I appreciate your expertise.

    1. Yes, adding some plywood on your attic floor over your existing insulation by about 2 per inch of plywood; however it is really not the best choice for insulating this space. The only reason I can see for you to go this route is if you are wanting to create flooring up in your attic to store things. If you want to bulk up the insulation, your money will go further if you invest in adding more traditional insulation or adding foam board.
    2. If you want to use Techshield, facing down toward an air gap, it will work fine to help keep radiant heat from escaping through your home's ceiling and into the cold attic. Another option is to drape radiant barrier foil in between your rafters before you instaLL the roof deck.
    Does that help?

  9. Rating: +1

    Positive Negative

    We will be replacing an existing roof due to hail damage. Our roof already has a 1/4" or 1/2" plywood decking WITHOUT A RADIANT BARRIER layer on it. Would it work to lay down another plywood decking WITH a radiant barrier layer on top of the existing plywood decking -- i.e. 2 plywood decks with a radiant barrier in between the 2 plywood decks? Would that work like other radiant barrier applications? Would there be any fire danger in doing so?

    This won't work unless you have an airspace on at least one side of the foil. By definition radiant heat is heat transfer by NON CONTACT across an air space. Without an airspace, you cannot even have radiant heat; therefore, you cannot have a radiant barrier. This is why an air space is REQUIRED when installing radiant barrier foil.

    One option you could try would be to raise the 2nd deck with furring strips. This is what I did on my home and did full sealed attic with foam insulation on the bottom of the lower deck.

  10. Rating: +1

    Positive Negative

    Hello Ed, Thanks for the great insight on your site. Although I have seen your video "How to Install Radiant Barrier Foil into a Cathedral or Vaulted Ceiling", my (non-attic) vaulted-ceiling situation is different than the one in the video. My rafters are made of 2x12s, so they can accommodate R-40 batts (non-faced; already purchased) and still leave a 3.5-inch air space on top for ventilation channels (soffit vents and roof vent already installed). Within this 3.5-inch air space, what would be the optimum placing of single-sided radiant barrier? 1) Attached to the underside of the sheathing (at the top of the air space) facing down into the air space? 2) Attached between the rafters at the point that would put it (face down) in direct contact with the insulation, but with the ventilated air space above it (like in your video)? (Also, would any dust accumulating on the paper side (which would face up) have any negative effect?) 3) Attached face down midway in the airspace, essentially creating two layers of airspace? Also, I read a several years ago that a two-inch air space was needed. Perhaps experience over the years shows that 3/4-inch is actually enough (like in your video mentioned above). Could you expound on that a bit? For reference, I’m using a light-weight, laminated metal roofing product (not black, but dark brown) that contains a layer of aluminum. I used furring strips to create vertical venting channels all the way up the roof. (I saw the exact same product, same color, in one of your other videos.) So, with the interior (below-the-sheathing) ventilation channels mentioned above, a cross section of my roof-ceiling structure would consist of: METAL ROOFING—1/2-INCH AIR SPACE—TAR PAPER—SHEATHING—3.5-INCH AIR SPACE (with RADIANT BARRIER at top, bottom or in the middle)—R-40 INSULATION—VAPOR BARRIER—WESTERN RED CEDAR. Thank you for your time and attention. Sincerely, Paul

    Ideally your radiant barrier would be closest to the outside (roof deck in this set up) with the air gap between the roof deck and the foil - just like in the video. If you are using a single-sided product then the foil side MUST face the air gap. I say a half-inch air gap is needed, but honestly that is the minimum, if you have more air - then use it.

    Just like you mentioned, these would be the layers:
    METAL ROOFING
    1/2-INCH AIR SPACE
    TAR PAPER
    SHEATHING
    3.5-INCH AIR SPACE
    RADIANT BARRIER
    R-40 INSULATION
    VAPOR BARRIER
    WESTERN RED CEDAR

    Watch a video of a radiant barrier installation under a metal roof here.

  11. Rating: +0

    Positive Negative

    I can't find any information about Radiant Barrier Plywood on your site or blog. I'm curious about Plytanium Thermostat Radiant Barrier Roof Sheathing from Georgia Pacific specifically. How can this work with no air gap?

    Radiant barrier decking works because in that application, the bottom side of the decking with the foil is facing down toward the open attic space. When standing in an attic you can look up at the roof line and see the foil in between each rafter; because of this air space, the foil works to block radiant heat from emitting (emissivity) into the attic space, and ultimately the home.

    However, the one down side to radiant barrier decking is that it doesn't take in to account thermal bypass on the rafters (meaning the heat is still moving through the rafter ends that are not covered with radiant barrier, and then radiates off the ends into the attic). Using radiant barrier across the rafter bottoms does not allow for thermal bridging, so in some cases people opt for the staple up method to get the best possible coverage.

  12. Rating: +2

    Positive Negative

    Ed, Thanks for the good info. I would like to add about 6 in of blown in insulation to my attic. This will make the insulation about 6 in above the ceiling joists. When I add the attic foil will it need to be stapled? If so, I would need to push the foil down to the ceiling joist to have something to staple to and this would counteract the effect of the added insulation.? Can attic foil just be laid in without fastening? Thanks, Alvin Green

    By putting radiant barrier on your attic floor directly on top of your insulation, AtticFoil works great in combination with regular insulation to make the regular insulation more effective. First, it will reflect the radiant heat loss BACK into the living space. Second, it will reduce the internal convection within the existing insulation. Laying AtticFoil out on top of the insulation will have the biggest impact on winter heat loss; think of radiant barrier as your first defense against heat loss, and traditional insulation as your second defense.

    When installing AtticFoil over your insulation in colder climates, please follow these recommendations for the best results:
    Roll out sections and cut around supports, ducts, and other penetrations. If ducts are on the attic floor, cover them too.
    Do NOT push the foil onto the insulation - just lay it over the top, like a blanket. If it peaks in certain areas, that's fine & ideal.
    Overlap the foil at least 2-3 inches; if you want you can secure the pieces together with foil tape, but it's not necessary. Stapling is also not necessary since doing so in your case would require compressing the insulation.
    Mark decking, or walk paths with colored tape or spray paint so you can tell where the flooring ends so as to prevent any accidents stepping through the drywall.
    You can NOT cover the foil with anything (i.e. flooring) or else you will eliminate the require air space for the foil to work.
    CRITICAL NOTE: You must be careful NOT to cover any source of moisture from inside your home such as a bathroom exhaust fan or a leaky can light. It is very important that bathroom and kitchen fans are vented to the outside of the attic, or at least past the foil insulation.

  13. Rating: +0

    Positive Negative

    So great to see your site..! I have open beam 4X10 rafter cathedral ceilings uninsulated & want to keep the look of raw wood inside. I want to insulate the top of the roof deck with rigid foam. Have a 4 in 12 pitch. Can I place radient barrier on the roof-deck under 4 inch rigid foam? Live in Woodland Hills Calif when temps are 100+ in summer - no snow or freeze in winter. The roof has extreme southern exposure so radient heat is extreme in summer and that's the target of insulation project. thanks for your help. Gil

    You can only place the foil under the rigid foam if there is an air gap either between the foam and the foil or the foil and the roof deck. If there is no air gap on at least one side of the double-sided foil, the radiant barrier will NOT work.

  14. Rating: +1

    Positive Negative

    My question is regarding combustibility of the foil bubble foil radiant barrier that I just purchased from Insulation4less...The representative of the company was completely unable to inform me of the products combustibility. Is it possible to be rated ClassA/1 fire rating and still be combustible? The combination of foil and plastic bubble would not seem to be very combustible. Thank you for your time!

    Thanks for your question! Yes, it is possible that the product can burn. Having a Class A/Class 1 fire rating for a radiant barrier does not mean the product will not burn. The classifications assigned based on the testing are just a measure of the burning characteristics of each product tested, not the fireproof-ness of the products. Aluminum covered radiant barrier products (like Original AtticFoil®) are pretty difficult to start burning and "combust" isn't the appropriate terminology. They won't spontaneously combust or start fire because of heat, they would need to be exposed to an open flame.

  15. Rating: +0

    Positive Negative

    I have used radiant barrier in past houses with amazing results, and am at it again on another old home. Question...We are putting pon a metal roof. Is it necessary to put both an underlayment and vapor barrior radient foil on under the battons? I will also use perferated RB in the attic.

    Because you are using purlins for the roof, I recommend you use an underlayment (for your waterproofing layer) combined with perforated radiant barrier foil on top of that, before the purlins. You need that self-sealing quality the underlayment will provide since you will be breaking the seal with the purlins. Since the underlayment will be your vapor barrier, you will go with the perforated foil instead of the solid.

  16. Rating: +0

    Positive Negative

    I recently install radiant barrier on the west, east, and south facing roofs of my hip-roof home with 2,000 sq/ft of attic space. I also added more soffit vents to meet the generally accepted NFA guidelines. I have been monitoring the attic temperature using the "kitchen foil tent" method explained in one of your videos. Though it's not exactly hot yet in Texas, we have had some 80 degree days and my attic is still getting as hot as 105 in the peak of the day. I guess I expected to see attic temps a little lower on this type of day. Is the fact that the north-facing is not done really hampering my results, or is this actually a decent air temperature on an 80 degree day?

    Air temperatures vary vastly depending on the ventilation, while surface temperatures are what are effected by adding a radiant barrier. Let's assume for the sake of an example, that your attic is 130F. With enough holes in your roof (ventilation), we could eventually get that temperature to drop to close to ambient (outside air) temperature. By forcing enough air through the attic space, we can drop the air temperature by 20F, 30F or even 40F. Ideally, after you install a radiant barrier the top SURFACE temperature of the insulation should be within a few degrees of ambient temperature, and the AIR temperature inside the attic should probably be within 10 to 15 degrees of ambient temperature. Personally I wouldn't get too caught up with the AIR temperature because it doesn't effect the home, the surface temperatures are what you need to address when it comes to comfort inside the home and lightening the load on the HVAC unit, which is what the radiant barrier affects. If it's really bothering you, take a look at your exhaust vents/fans; you mentioned soffit vents for intake so take a look at what you are you using for out take venting to start.

  17. Rating: +0

    Positive Negative

    Ed, Thank you so much for all of the info. I have a playhouse in Southern California I am constructing for my daughters. My rafters are 2x4 and I would like to roof it with single sided radiant osb. The ceilings are vaulted and I was hoping to finish the underside of the rafters with strips of pine to be a finished vaulted wood ceiling. Is the is the 3 1/2 inches between the pine and the radiant layer on the underside of the roofing osb sufficient. I am assuming I won't need additional insulation and from what I've read that would actually hurt. My layers then would be (from top to bottom) Shingles Tar paper OSB with radiant layer facing down into room 3 1/2 air gap Pine covering the ceiling Will that work ok and will i benefit from the radiant layer ? Thank you John

    That would work beautifully! With the air gap the radiant barrier is going to block 97% of the heat from entering the playhouse - it will work great! If you are not conditioning the area, then just make sure there is plenty of ventilation as that will help keep the air temperature down close to ambient.
    On another note - if you construct the playhouse in the shade, you will get the same benefits as you would from adding a radiant barrier, without the work - just FYI!

  18. Rating: +0

    Positive Negative

    I have been looking but unable to find any information concerning the installation of rigid polyisocyanurate radiant barrier foam for my application; most likely because the application is unique. I am refurbishing a 32' travel trailer. The poorly installed fiberglass insulation is being removed (major gaps exist). Most RV's are ovens in the summer and freezers in the winter when poorly insulated (as this one is). I found the R-Matte Plus 3 R-5.0 3/4" foam insulation with radiant barrier at Home Depot. I took one sheet home, cut to fit in between the 2x2 wall beams and it appears to fit very nicely. Installation was a breeze too. The outside of the travel trailer is metal. The question is which way do I install the foam, with the radiant barrier on the inside of the trailer or outside? There is a small air gap between the outside metal and the wall beams because the metal does not set flush against the beams. I was considering putting the barrier towards the outside, then use fiberglass to further insulate the small gap between the foam and the inner wall. From reading through the FAQ's though I'm now considering putting the fiberglass on the outside metal wall followed by the radiant barrier side of the foam on the outside, and keeping the foam flush with the inner side of the beams (inner wall). This would give the air gap that is mentioned in several FAQ's. Or should I completely leave the fiberglass out of the picture? Or should I push the radiant foam (radiant side out) into the frame so a very small gap exists between the outside metal wall and the radiant foam? I'm really not sure what's going to give me the best insulation in this situation. I appreciate any advice you can give on this unique situation.

    The foil needs at MINIMUM a half inch of space. I'd shoot for 3/4" to play it safe. Ideally the foil needs to be closest to the OUTSIDE, as your FIRST line of defense against the heat gain. Then, finish the rest of the walls with the foam and fiberglass combo to get a good R-value to slow down the conductive heat that will emit from the foil (about 3%). Take a look at this page for an idea of how an install in a tight space like that can work: Radiant Barrier Foil in a Vaulted ceiling & Using Radiant Barrier in Walls.

  19. Rating: +0

    Positive Negative

    I am fixing up a vintage travel trailer in SE Az. The walls and ceiling have 1 1/8" to 1 1/4" space between aluminum skin and interior panel. I read the article about using furring strips and foil, then insulation. If the insulation has contact on the inward side with the insulation, does that negate the low emmittance of the foil? Would foil bubble product work any better" would the bubble side act as a buffer between the foil and the insulation and diminish conductance?

    No, the foil still works using its reflective property to reflect 97% of the heat gain from the outside. When the heat is coming from inside, the insulation slows that conductive heat loss and the foil, because it has an air gap on the backside of it, works to prevent heat from emitting through the foil layer into the air gap created by the battens.

  20. Rating: +0

    Positive Negative

    Can I use a radiant barrier on an open beam cathedral ceiling. We are replacing a shake roof with a composition roof.

    Yes - you can. You will need to install the foil closest to the roof deck, with the proper air gap. Look at this page on AtticFoil.com for more information on installing radiant barrier in a cathedral ceiling

  21. Rating: +0

    Positive Negative

    What's the difference between radiant barrier and bubble foil products?

    Typically both have an aluminum layer - that is what is doing the job of reflecting the heat. In the bubble products you typically pay about double for a thin layer of bubble material (or basically air) and oftentimes it's an unnecessary expense since air is plentiful in an attic space. Read more here: Compare Radiant Barrier Foil with Bubble Foil

  22. Rating: +0

    Positive Negative

    I live in Texas in an older home with little insulation. Is it best to have more insulation before installing radiant barrier

    I'd recommend you add a radiant barrier first, before you decide to add more insulation. Also, please refer to this article for more info on saving energy in hot climates: Four Silver Bullets For Saving Energy In Hot Climates

  23. Rating: +0

    Positive Negative

    I'm building a brick home currently. I bought radiant barrier osb for decking and also for the exterior walls. I will obviously have an air gap between the osb and the brick, but if I put a vapor barrier over the osb directly will it cancel out all of its heat reflective capabilities? And should the foil face the brick or the inside of the home?

    If you cover the foil layer with ANYTHING then YES, it will negate it's reflective properties. Radiant heat by definition is heat transfer from one object (the hot object) to another object (the cooler object) by NON-CONTACT. When there is contact with both sides of the foil, the heat is conductive and aluminum is a very conductive material, so it will work against you! The decking needs to face DOWN, toward the open attic space, in order to work properly.

  24. Rating: +0

    Positive Negative

    I have a 45 year old golf villa in Hilton Head SC and the vaulted ceiling is nothing more that 3/4" cedar tongue and groove board, with the roof shingle on the outside, so ther is no insulation or cavity to fill. I heard that there was a radiant barrier/sheetrock product that I could install directly to the ceiling as you would install sheetrock. Are you familiar with any such product or have any other recommendation.

    I am not familiar with any such thing - there is no such thing as radiant heat between materials that are touching. For radiant heat to even exist there MUST be an air space; without an air space you don't have radiant heat, you have conductive heat. Plenty of products work to slow conductive heat (they all have r-value). The only way to stop heat and reflect it back is for radiant heat to be present and then you can reflect it with a radiant barrier. To do this there needs to be at least a 3/4" cavity of air for the heat to convert to its radiant form so you can block 97% of it with a radiant barrier. Check out this page for more information: Radiant Barrier in Cathedral Ceilings

  25. Rating: +0

    Positive Negative

    I have a attic storage area that currently has paper faced fiberglass batt insulation installed in the roof joist. A ton of radiant heat is still emanating from the roof joist. Is it a good idea to just install some foil faced polyisocyanate foam board across the roof joist (leaving the batts in place)and then add some 1/2" furing strips to attach the drywall (to leave an air space between the drywall & the foil facing)? Would the foil facing need to face the batts in the roof joist or face the drywall? Thanks in advance for your professional opinion.

    Unless you are sealing up that space (with the drywall) and planning on conditioning it (with A/C or heat), then you don't really need that fiberglass insulation up on the roof. Otherwise, you need the foil to be the FIRST layer up there - with the air gap between the roof deck and the foil, then add insulation and then you can use foam board and drywall. For full installation instructions, and a video, please see this page: How to Install Radiant Barrier in a Cathedral Ceiling.

  26. Rating: +0

    Positive Negative

    I just bought a 1968 straight ranch in Austin, TX. 102 degrees here today! The attic is a mess with blown-in wool/stapled pink insulation, and probably none on the vaulted ceilings.....house has 2 wings and I cannot crawl through hall....can I paint the asphalt shingle roof with radiant barrier paint, instead of cleaning out attic, etc. Also, is putting foil on floor wherever I have access to floor as good as putting it closer to rafters? Thank you.

    The paint is a waste of money - don't even bother. You're better off just putting foil directly over the shingles! (Though it would probably bother your neighbors and be an eye sore.) You can put the foil over the insulation wherever there is not storage or other things - it will still help better than no foil. Radiant Barrier Foil has a cumulative effect, so the more you can get installed, the better your results and partial coverage does help. Try to aim for at least 70-80% coverage to see a big improvement. Navigating the attic space is the hardest part of any install, but if you can get up really early in the morning and knock some sections out, you'll do fine. Good luck!

  27. Rating: +0

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    Hello. I live in Paraguay (South America). I need to get some expert info on this product. We have something similar but not AtticFoil. I have an outer birck wall and want to finish the inside with drywall. I was thinking of installing the foil between my outer 12cm thick brick wall and the drywall interior finish. Will this work? Will this not creat condensation? I will have my electrical and water in between the brick and drywall also. Do all foil products basically work the same? Can you ship your product to South America. Thanks

    Yes, this will work. Adding radiant barrier in a wall is simple and reaps good benefit when the wall is one that catches sunlight from outside. Remember, you have to have an air gap on one side of the foil. Click the link to go to the installation page to see how it is done. Condensation can be combated by having an AIR TIGHT wall. Foil products work on the same physics principles, but not all are created equal. I don't currently ship to South America directly, but some of my customers use a freight forwarder to get the product.

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    I live on the gulf coast. I'm concerned that painting the underside of my roof in the attic may cause rot in the roof decking itself. Your thoughts ?

    I don't recommend the paint for other reasons. You can read why here: Why radiant barrier foil is better than radiant barrier paint.
    A perforated radiant barrier foil will be the best product to use in a vented attic to keep the radiant heat from coming in through the roof and ultimately into the home. You can see the install instructions here: How to Staple Foil to your Attic Rafters to Block the Heat

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    If I install radiant foil to my attic rafters, should i install Styrofoam vent chutes on attic ceiling before putting on foil? I assume I can put the foil in my garage attic as well? and lastly, can I lay insulation batts over blown insulation or do I have to add just more blown Insu. thanks Chris

    You don't have to install styrofoam baffle vents, but you can. If so, you'll just make your gap in the foil for proper ventilation before the second run. Start the first run down low as far as you can get and then start the second run about 3 to 6 inches above the first one. This gap allows air into the attic to help w/moisture control.
    Check out this link for: The Best Way to Install Radiant Barrier Foil in a Garage

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    whats the best radiant floor heat insulation from the basement side.

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    IF I AM PUUTING ON AN ENERGY STAR RATED COOL ROOF (STANDING SEAM) WILL A RADIANT BARRIER BE NECESSARY SINCE THE ROOF SHOULD NOT GET MORE THAN TEN DEGREES HOTTER THAN THE AMBIENT TEMPERATURE?

    Even with a cool roof, radiant barrier will take it the last mile. The roof deck below a cool roof and radiant barrier will basically stay at ambient temperature.
    This means that virtually NO radiant heat gain into the attic or home through the roof. Radiant barrier under metal/tile roofs is the fastest growing use of radiant barrier. It's cheap, easy and VERY effective.

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    I AM RE-ROOFING A HOUSE USING A WHITE STANDING SEAM METAL. I WANT TO HAVE A SOLID BACKING BENEATH MY METAL AND THE HOMEOWNER WANTS A RADIANT BARRIER. WHAT DO YOU SUGGEST THE BEST ROUTE?

    If you're using a deck, try TechShield - it's a radiant barrier covered plywood used in roofing. It works well and is pretty economical.

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    My son plans on using foil radiant barrier on top of and contacting a cement slab. He is running pex tubing on top of the barrier and below subfloor and tile. Is the contact of the concrete nullifing the barriers effect. There is a 1" air gap between the barrier and the subfloor. Thank You.

    No. On a double sided foil product, only ONE side has to be open to an air gap. As long as that one side is free to the air space, then the foil will work to do its job.

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    Guru I'd like to ask about the use of radiant barriers below ceiling joists. I currently have a home remodeling project going through a phased approach which currently has no wall insulation and old blown in 'pink' tufts within the ceiling joists. The roof structure will be replaced with a complete roof system in the near future so I only need to address the area (25 x 16) master suite area at this time. The attic area above the master suite will have a plywood/osb type floor for 'storage' use so a radiant barrier on top of the ceiling joists might be compromised with screw hole, trapped dust etc.. My question is simple - if I apply a permeable radiant barrier between the ceiling Sheetrock and the joists (we would furr between the RB and the Sheetrock to leave an air space of about .75") and insulate with regular 'pink' batts, would we have moisture problems within the insulation. Note - we are not addressing the 'heat through the roof' issue's since the house is nicely placed under shade trees and has no summer heat intrusion problems. We're only interested in the rectangular 'box' of the master suite between the walls, slab and ceiling. Any info or advise would be greatly appreciated.

    There is no way to truthfully promise you won't have a moisture issue. Why? Because moisture has little to do with adding the radiant barrier and a whole lot more to do with how air tight your wall assembly will be. If it were me, I'd set it up like on this webpage: How to Install Radiant Barrier in a Wall
    Obviously your layering would look a little different with the foil closest to the inside of the room, but the idea is to incorporate some foam board to help seal the wall air tight. For an extra air-tight wall, I recommend putting a bead of caulk on the face of the studs before the foam layer (or before the sheetrock layer). Be sure to caulk between the bottom plate of the wall to either the concrete slab or the subfloor to reduce air leakage under the wall as well. After doing this you can add the foil and then create your air space before the sheetrock.

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    What is the radiant drape material costs for a 2100 square foot house? I live in New Braunfels and my home was built in 2009 without a radiant barrier. Is the drape method the best choice for post construction application. Thanks

    Pricing here: http://www.atticfoil.com/products.html
    The best retrofit installation application is either stapling it to the underside of the roof rafters inside the attic. Installation instructions, click here.
    Or laying it over your insulation on the attic floor. Floor install instructions click here.

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    I have a block exterior wall home. Walls are furring strips . It's a summer bungalow with no heat or exterior insulation . We got flooded in Sandy and cut out drywall and found a foil paper on the furring strips . Block are tarred on inside. Do I need to get the same type of foil to replace or is there some other type of material

    You don't have to use the exact same material, but you should incorporate a radiant barrier back into the wall system. To see how to do it, click here: Installing radiant barrier in a wall cavity.

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    Hi Ed. I watched your video on how radiant barriers work and from what I understand having a void between the foil and heat source is very important. Radiant barrier plywood has really taken off with some roof installers in our area. My question first is what do you think about radiant barrier plywood. we are in the Kansas City, MO area and there are a lot of wood shake roofs that are installed over a spaced decking. When homeowners tear off their wood shake shingles and install a solid deck and asphalt shingles often roofers will install a radiant barrier plywood to the spaced 1" x 4" decking sandwiching the foil between the plywood and the spaced decking. Does this have a negative effect on the performance of the radiant barrier? Does sandwiching the foil between the plywood and spaced 1" x 4"'s reduce the effectiveness of the radiant barrier? Thank you for your response.

    I like radiant barrier decking even though it's not quiet as effective as stapling foil to the bottom of the rafters. Bang For The Buck it's usually the best way to go for new construction. Recently, we have had many customers combine BOTH radiant barrier decking with AtticFoil installed below the rafters with AMAZING results.

    As for installing over the existing 1x4 laths, you WILL lose the radiant barrier benefit wherever the foil is "sandwiched" between the old lath and the new deck. Typically, this will be about 50% of the roof surface. So, you will reduce it's effectiveness by about 50% compared to a taking off all the laths and installing directly over the rafters. All things considered 50% is still a lot better than 0% and since the cost of radiant barrier decking is pretty cheap it's probably still worth it. One option is to remove ever other lath. This greatly improves the effectiveness and you should still maintain the structural benefit of having the laths. For more info, see: Partial Coverage with Radiant Barrier works!

  38. Rating: +0

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    Would a radiant barrier be cost effective if it were used close to both the inside and outside surfaces of a wall and cathedral ceiling insuring you have the required air gaps and the 2 barriers seperated by a layer of 2 inch closed cell foam. The reason being, during summer months keeping heat out and during the winter for keeping heat in. thanks for your info

    You only need one layer of foil for it to work -and work year round. The best way to incorporate spray foam is to use the wall method: Adding Radiant Barrier to your Walls and then instead of batt insulation, you can use foam board over the foil and then spray foam onto the foam board to finish the wall cavity.

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    About to build a new home. I plan on installing radiant barrier plywood to my roof sheathing, I have soffit vents with ridge vents. would I benefit from installing an additional radiant barrier below my rafters which would allow about 6-8 inches of air gap between the two radiant barriers and still allow air flow from my soffit to ridge vent?

    More and more we are seeing people add AtticFoil radiant barrier across the roof rafters below their Techshield (radiant barrier OSB) with good results. I even did the same thing on my home and I have had amazing results! Additionally, an official study has been done on the effectiveness of Techshield versus radiant barrier stapled across roof rafters and it found that the most effective application for a radiant barrier is to staple it across the rafters (this study will be officially published at the end of next year).

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    I have a hot yoga studio in Michigan. We installed 4 radiant heat lamps which focus the heat in zones. They heat to 110 F. I also have 5 enerjoy panels which are long wave infared heat panels they heat up to 113F. I am trying to get the heat up to 105 F. With the amount of power I have in that room it should be up to 150 easy! But instead I am stuck around 85 degrees. The room is in a old building with high celings. 24'X 28'X 25' High. The floor is insulated along with 3 insulated walls. There is a 24' brick wall on one side of the room and the cold Michigan winter right outside of it. I am wondering if my heat is passing through the brick. What can I do to get it hot enough?

    First, the best approach is to make sure the area is air tight. If you have an exterior brick wall in the interior, then that's probably your #1 source of air leakage. I'd suggest you get it sealed air tight first, then, install a radiant barrier on any and all walls that you can to help retain 97% of the heat your heaters are putting off (keeping in mind not to install it directly next to the heaters, but give it some air space and "breathing" room).

  41. Rating: +0

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    will your radiant barrier, when installed between two layers of sheetrock, effectively eliminate thermal tracking evident on a cathedral ceiling.

    No. Radiant barriers must be used in conjunction with an air gap. When there is no gap (as in the case of sandwiching the foil between sheetrock layers) the foil is NOT a radiant barrier but rather a CONDUCTOR now and this will only promote heat gain, not block it as intended. You cannot sandwich a radiant barrier and expect it to work, it won't.

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    I'm confused about the air gap in relation to pre-laminated roof decking. If an air gap is required, then how can it work properly if if the radiant barrier is directly attached to the underside of the decking? thanks for the help Stephen

    It's actually very simple: the foil side is placed downward, toward the attic. All the air in the attic is the airspace! Read this article to get all the details: Techshield Compared To AtticFoil® Radiant Barrier

  43. Rating: +0

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    Can I put foil radiant barrier over the existing foam ventilation baffles that run between the roof rafters? Thanks,

    Yes, you can, but remember: radiant barrier foil must be open to an air gap on at least one side in order for it to work. This means wherever the foil is touching the baffles on one side and insulation on the other - IT WILL NOT BE WORKING as a RADIANT BARRIER. If it's just touching the baffles on one side and open to the attic air on the other side, then you're good to go. Also, remember to leave a space before putting the next horizontal run of foil - so the air from the baffles can come into the attic and also some of it can stay between the foil and the roof.

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    Hi, I live in Pichilemu, Chile with a coastal climate similar to that of Santa Barbara, CA. I am currently building a small studio which I'm going to side and roof with corrugated zinc sheets. Common practice here is to put tar paper down below all roofing and siding materials. I wanted to add a radiant barrier and found some kraft paper backed foil here at one of the building supply stores (here is a link to the product: http://www.easy.cl/easy/ProductDisplay?mundo=1&id_prod=11700&id_cat=0&tpCa=4&caN0=2267&caN1=7957&caN2=7895&caN3=0). I was planning on rolling out this covering directly over the tar paper and creating a 2" air space with 2x2's between the metal and the foil. However, I don't believe the foil product I bought is permeable. Will this be an issue, i.e. is it necessary to lay a permeable layer over tar paper? I can't find a permeable foil here in South America and wanted to know if I would just be better off forgetting the idea of a Radiant Barrier. Thanks!

    Yes, it is necessary to have a PERFORATED (permeable) layer over the tar paper because the tar paper is also a vapor barrier. Having two vapor barriers layered on top of one another is not advisable. If you cannot get a perforated product there, have you considered letting your foil/kraft paper be your underlayment instead of the tar paper? In some new construction, a solid (vapor barrier) radiant barrier has been used in place of the traditional tar paper because it offers the benefit of both a vapor barrier AND a radiant barrier (when installed with the proper air gap) all in one.

  45. Rating: +1

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    I am replacing the interior walls in my 1994 travel trailer. I would like to use a radiant barrier. can i layer radiant barrier and insulation if so where do I leave a air space. I wanted to use insulation also for noise reduction. or should i just use radiant barrier. I live in Texas and in the summer when i would use it most it can get to over 100 degrees.

    First and foremost, without an air gap on at least one side of the foil, it will NOT WORK. So, assuming you can get a gap between the inside walls/roof of the trailer and the foil, then you'll be fine to then layer in foam, etc. If you are going to be CONDITIONING the trailer, then you need to seal it airtight and the foam will help. Otherwise, if you won't be cooling/heating the trailer, then you don't really need r-value. Basically you just need a layer of foil to stop the heat gain.

    It will work best if the air gap is between the walls and the foil, so that you can fill the trailer with whatever. Otherwise, if you attach the foil directly to the walls and roof of the trailer, you have to make sure nothing touches the foil because the foil will need the air inside of the trailer as an air space. Does that make sense?

    Also, any and all sides that will be in sunlight should be covered from the inside; so walls and roof.

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    Hi Ed Great Site very informative! I am currently doing my roof and want to have a radiant barrier. The roofer wants to put the OSB w/radiant barrier on top of the spaced sheeting that is on top of the rafters. Is that correct? Thanks so much! Daniel

    Yes, the foil side of the OSB should face DOWN, toward the open attic space.

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    I AM INSTALLING A METAL ROOF OVER PLYWOOD I WILL USE 1 1/2 ISO BOARD BETWEEN 2X4'S NAILED TO THE top side of TRUSSES AND A WATERPROOFING MEMBRANE OVER ISO WHERE SHOULD THE RADIANT HEAT BARRIER BE INSTALLED. ON TOP OF membrane ,on top of iso ,under iso ,OR ON THE underside of PLYWOOD INSIDE building

    If you will have a gap between the metal roof and the battens, you can lay the foil OVER the foam board so it will be open to the air space before the roof. Watch the install video here: Installing radiant barrier foil under a metal roof.

    Otherwise, you should look in to trying a foil covered deck, with the foil facing down, toward the open air space below the deck. More info here: Techshield Compared To AtticFoil® Radiant Barrier

  48. Rating: +0

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    Mr. Ed – I have a small attic with a split heat pump unit in it along with the duck work. The attic size is about 1920 sq ft. this is a duplex. At the peak of the roof the height is about 4ft 8in. I have three wind turbines on the roof and gable vents at the end of the duplex. I notice when the a/c first comes on it blow warm air before the cool starts coming out. Would adding radiant barrier help this issue? Also can I place the radiant barrier directly to the attic ceiling or do I have to attach it to the attic rafters? I’m finding different answers to this and I’m unclear on what would work best for my attic. Also due to my budget I would like to do this myself. Do you this is a DIY job? Also I have issues in my crawlspaces; joists that are cracked and weak joists. I know that sealing off the crawlspace with a vapor barrier is the way to go. Now my questions; 1) what the average cost to have the done? 2) what product would you use? 3) I live in Nashville, TN do you know of any companies in my area that does good work? 4) Do you think this is a DIY type of job? As you see I have issue with my home’s insulation – helps for any suggestions you have.

    1. That's a loaded question - one that I can't accurately answer. The best response is: it depends. On a lot of things. Typical installation costs range from $0.25 a sq ft installed to $3.00 a sq ft installed.

    2. You just need an aluminum radiant barrier that is perforated: AtticFoil Radiant Barrier is perfect for this.

    3. I don't have anyone in that area to recommend.

    4. Yes, you can do this! Access around the attic is probably the single biggest factor people face when installing AtticFoil® Radiant Barrier.  For more info, take a look at this page for tips and tricks: DIY Radiant Barrier Installation Tips and How to Staple Radiant Barrier Foil to the Rafters in Your Attic.

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    We have a metal roofed horse barn. The attic (loft( is about 35' X 60' and about 15 ft. tall at the peak of the gable. The flooring in the loft is 2 layers, the old wood with plywood on top. The loft has some venting provided where the metal roof attaches to the sides, but it gets hot in the loft and we leave the doors up there open a foot to provide more ventilation. The horse stalls and corrals below are just too hot. We keep a floor fan going for them, but that doesn't help a great deal. We live in NE Texas. Our only goal is to reduce the heat in the barn, especially in the horse stalls below. What is our best application(s) of a radiant barrier to reduce heat on the ground floor of that barn? Thanks.

    The best way to do this is to add the radiant barrier so the foil is the layer closest to the exterior sheathing, with the proper air gap on at least one side of the foil. On non conditioned spaces like barns and metal buildings, there is nothing better to temper the heat gain that a radiant barrier - it will BLOCK 97% of radiant heat.

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    I have a 4/12 shed roof. My boyfriend used tech sheild and has no clue what to do now. It's collected a lot of condensation being as we are building this house ground up. It's been dripping water. How do I go about preventing that and how should I insulate it

    Condensation forming is a good sign that there is not enough/proper ventilation moving across the underside of the roof. If the structure is a shed - you really won't find a great way to stop this since those type of buildings are meant to be non-conditioned/non-living spaces. The only way to really stop the condensation is to treat it like a home/living space whereby you SEAL, SEAL & SEAL the area up air tight and then insulate it with a radiant barrier and regular insulation toward the inside while having adequate ventilation moving through the attic space. Then you can condition the space with little concern for the condensation.

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    Does anyone make a radiant barrier product with the air gap internal and not requiring an external air gap. I would prefer it to be somewhat flexible if possible. I am currently using custom silvered glass panels with small spacers. I have considered using inflated silvered Mylar but long term reliably is a problem. I do not care about conduction or convection just infrared radiation.

    Not that I'm aware of. The problem is that for a radiant barrier to work, it must have an air gap on one side or the other. Bubble foil products claim the bubbles offer that gap, but it's highly contested that the air in the bubbles isn't a true air space for the radiant barrier sides to work. To get a radiant barrier in use, you're going to have to use air gaps.

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    I live in a 22 year old cape cod home in Virginia. I am installing radiant barrier panels (Enerflex) in both the attic and knee walls. In the knee walls I currently have batt insulation, I plan on removing the batt insulation and installing the panels directly to the exterior wall rafters. Should I put the batt insulation back up against the new radiant barrier? The knee walls have the foam baffles attached already. So it would be foam baffles, radiant barrier panel, and the batt insulation.Thanks. Also should i pack insulation on the top and bottom or leave that open for air flow? I have sofit air vents as well. Thanks in advance. Nicole

    Nicole,
    This does not sound like it is going to work, mainly because of how Enerflex is installed. Essentially you'd have the baffle, the enerflex panel on top of that (with little to no air gap), then the insulation on top of the Enerflex. So the foil is sandwiched in between the baffle and the insulation, which means it WILL NOT WORK AS A RADIANT BARRIER.
    Second, the radiant barrier should really be the LAST layer, so it uses the attic air space as it's required air gap. Take a look at this install page specifically for KNEE WALL applications: http://www.atticfoil.com/applications-a-uses/kneewalls.html

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    Hi. I found this stuff called Reach Barrier Silvertanium at home depot, and it says I can use it as house wrap? I live in the desert, so is that a good idea? Does it do the same thing Tyvek does? Will I still need to use the pink batts? Thanks so much! The more I read, the more I'm confused 🙁

    Reach Barrier isn't going to give you as good results as AtticFoil since Reach only blocks 95% and AtticFoil blocks 97%. Plus, the cost of Reach Barrier is significantly more than AtticFoil Radiant Barrier. I can't say for Reach if it performs like Tyvek, but AtticFoil does; it provides an air barrier and a drainage plane for the exterior of the home. Here is the page on wrapping a house with radiant barrier that gives you all the info you need: http://www.atticfoil.com/applications-a-uses/house-wrap.html

  54. Rating: +1

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    My home built in 2013 already has radiant barrier osb but it is still very hot in my attic. Can I add your radiant barrier to the bottom side of my rafters to get better results?

    Yes, you can add AtticFoil across the bottom of the rafters to further eliminate any heat that is entering the attic via the rafter ends. However I should point out that saying your attic is still very hot leads me to believe that you are describing the AIR temperature in your attic - which is directly related to the ventilation in your attic. You can add another layer of radiant barrier, but you should also examine your ventilation to make sure you have an adequate amount and that it's not obstructed by anything.

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    I am planning on building in Southeast Idaho! the house exterior walls will most likely be Raycore SIP panels. The Raycore panels have a radiant vapor barrier on both the inside and outside surfaces. I plan on placing an artificial stone on the exterior of the house. My first question is does the the exterior air gap need to be able to vent via weep holes at the bottom and some others means at the top, or will the air gap function properly if it can't chimney the heat out the top? My second question is what if anything do I need to do on the inside walls since there is foil there as well? Thank You, T. Buti

    1. You don't HAVE to vent the air - the foil can work with a dead (non-vented) air space just as well as with a vented one.
    2. You only need one layer of foil to get great results - a second layer will provide minimal benefit that close to the initial layer. That being said, you can just put insulation right up against it (so it is not acting as a radiant barrier) or you can go ahead and incorporate an air gap between the foil and the insulation to get a second layer of radiant heat block.

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    Hello Ed. I am building a house in Birmingham Alabama. I am going to use Tech shield foil faced plywood over OSB. Would you recommend using ridge vents or turbines to ventilate the attic? I prefer to use ridge vents as it would give ventilation the entire length of the roof. There will of course be soffit vents. Your thoughts. Thanks. Howard

    Howard, I think you mean you will use TechShield INSTEAD of regular OSB? The TS product needs to face the attic (air) space. Many people also add a layer of radiant barrier inside the attic even with the TS product because of the thermal bridging that still takes place through the rafters. National testing has shown that foil over the rafter ends is the MOST effective way to get a radiant barrier up, with TechShield coming in second. Just some food for thought. Another option would be to use TS on the roof and then add a layer of AtticFoil to the gable ends, depending on what else you are using on them.
    I think ridge vent is great as long as it’s the high profile “baffled” type.

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    I live in Phoenix AZ and am building a new house. My question is when using a radiant barrier insulated foil installed on top of the waterproofing layer and under the wood battens for a roof tile, should I install the radiant barrier on the entire roof of the house or just the roof of the living areas? I would say the whole roof but don't know what the pros/cons would be. Thanks.

    It's easiest to just do the whole roof, but obviously the overhangs and porch areas aren't going to see the same impact as the living spaces. If you're trying to be economical, then just do the living areas. Garages and porches do benefit from the foil though - in non conditioned spaces like those, there is nothing better to temper the heat than a radiant barrier.

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    I live in ft worth Texas and have the non perforated radiant barrier installed under the rafters. Should I be concerned with moisture in the attic?

    In a vented attic space you should have a perforated product exactly because of moisture concerns. Why? Because you want dry walls and ceilings and the perforations allow for moisture to flow freely and escape/dry out. Over 70% (that's 7 out of 10) of home issues are due to mold, mildew, rot, decay, etc. and moisture is the common theme. Dry products don't grow mold, rot or decay; therefore, moisture in wall and ceiling assemblies is not a good thing. This is why in an attic you should choose a perforated product (that allows moisture vapor to pass through freely) over a solid product (that traps moisture behind it).

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    I have a three year old home outside of Houston. The attic is very high. It has the AC unit and water heater up there. The roof was made with the radiant barrier plywood sheathing. It gets very hot up there starting in May. I have also noticed mold on the outside of the AC unit, particularly where the conductors insert into the unit. There is blown in insulation. I would like to know if there is an additional insulation I can install to bring down the attic temperature?

    You didn't specify, so I assume you're discussing the AIR temps in the attic? It sounds like, from what you described, that you need proper ventilation in your attic and you need more of it. Adequate ventilation will keep the air temps lower (close to ambient with the radiant barrier decking) and also keep thing DRY (ie. prevent moisture from accumulating, leading to mold/mildew).

  60. Rating: +0

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    Hi. I live in Nicaragua where it is 85-90 degrees year round. We have a white metal roof with steel trusses and purlins but no insulation. We would like to install a radiant barrier. What is the best way to attach the radient barrier to the underside of the steel purlins?

    Truthfully there is really no easy way to attach radiant barrier to heavy gauge metal. One option is to attach something to the metal that you can staple the foil directly on to. Many of our customers have had good success by cutting 3/8" thick OSB or Plywood into strips about 1-2" wide. Then, they attach the wood strips to the metal framing with either with screws or adhesive. Once the wood stripping is up, you can easily use 1/4" staples and attach the foil to the wood. You can also try magnets or even zip-ties as well.

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    I am redoing an exterior wall (north texas) of a west facing enclosed porch. The walls do have insulation but we are removing the siding and sheathing. A friend has given me some Norbord sheathing with the one side that has the radiant barrier covering. He said this would be good to mitigate the heating I have in this area. I have a plywood siding and I assume I need an air gap between the two. I'm not sure about the number and placement of the furring strips.

    Yes, you will need to use some furring strips to create the gap for the radiant barrier to work. You don't need many, since the sheathing is rigid and won't sag in between the strips. You could space them 2-4 ft apart and I'd stagger them whichever direction you add them, to keep air movement simple.

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    Hello. I will soon be replacing a roof and also having vinyl siding installed over masonite siding on our 1 1/2 story home in Mississippi. I plan to install radiant barrier in the attic - hopefully before summer. The house has gables so I plan to use radiant barrier on the vertical wall of the gable in the attic as well. My question is whether I can or need to take advantage of the vinyl siding install to improve the walls of the house by installing radiant barrier under the siding. In other words, is there enough potential gain to make it advantageous to do what is necessary to properly add radiant barrier to the exterior walls, under the vinyl siding? Also wondering if putting up radiant house wrap on top of the masonite siding, under the vinyl siding, would be a good idea even if not allowing the proper air space. The house is insulated fairly well, built in 1979, so I would like your opinion on whether or not I should make an attempt at putting radiant barrier on the walls, under the vinyl siding. The installer will add 1/4 foam board under the siding for a reasonable cost but I don't know if that is even worth it or if the effort really needs to be on radiant barrier. Finally, is the most opportunity to save on electric bills / blocking heat from the house by installing radiant barrier in the attic? If the walls are of minimal advantage, maybe I should skip trying radiant barrier under the siding and concentrate on the attic. Thanks for wading through all of this. I realize your advice will only be based on generalities on not on my specific home.

    Yes - it's worth it! Read more here about Adding Radiant Barrier Behind Vinyl Siding to Reduce Heat Gain

  63. Rating: +0

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    Hi, We are installing radiant heat floors (hydronic) over pier and beam, and concrete. Can/should we use radiant barrier over either the plywood deck-over joist floors, and/or the concrete slab floors. Note that the wooden decking floors are insulated with spray foam underneath, over a crawl space. The house is in Central Texas. Thank you in advance for your answer!

    Yes, you can use radiant barrier as part of the system in radiant heat flooring, as long as the foil is open to an air space. The page here details how to do this: http://www.atticfoil.com/applications-a-uses/radiant-heat-flooring/over-non-conditioned-space.html

  64. Rating: +0

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    About to replace a cedar shingle roof. Also plan to create attic living space . Can we place (drape) radiant foil directly under the shingles ie draped over the lathe? Impact on shingles. We have thought about also using foam board laying on the ceiling rafters above R19 batts. Any better ideas ?

    Depending on the spacing of the laths, you might find that the majority of the foil is touching the laths than not, so in that case it probably wouldn't be worth the investment or effort. If you are making living space in the attic - then this is the way to install the foil to get the BEST results: Installing radiant barrier in a cathedral ceiling
    Also do the knee walls of the living space: Using radiant barrier on knee walls of bonus rooms

  65. Rating: +0

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    I am building a pole barn in north Louisiana, andI am trying to figure out the best way to prevent condensation. I have concrete floors with vapor barrier underneath, and want to use a solid radiant barrier under the metal roof, to act as a vapor barrier, also. It will only be heated occasionally, and nothing but fans for summer time. Will attic foil work for this, or do I need to go with a insulated product to prevent condensation?

    There is no product that is a solution to condensation forming on a vented structure, it's the PROCESS of construction that solves this. This means that no matter what product you use, if you don't seal the building up air tight (like a home) then it will still form condensation/moisture. Since it's not a living space, preventing moisture is near impossible; therefore the next best thing is to allow that moisture every chance to dry quickly. It means you need to have lots of ventilation in the barn (think air moving constantly throughout). This will keep the air temps down, but most importantly it will help keep the building DRY and prevent the roof dripping or the walls "sweating." Incorporating our foil into the roof and/or walls will help stop the heat gain, which is going to make the interior of the barn cooler (ideal is equal to ambient temp). So, get the foil on all sun-catching sides of the barn and then get as much ventilation moving through the barn as possible. This will help dilute humidity in the barn and keep it dry and the foil will keep the items under the roof cooler since they will not absorb radiant heat coming off the roof. Check out www.WareHouseFoil.com for full install instructions and photos.

  66. Rating: +0

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    Hi Ed! I am a 50+ yr old female trying to figure out a way to cool down a 30+ yr old covered patio which is attached to my house with 3 walls and has a single layer pleated aluminum panel sloped roof. I had 2 ceiling fans installed but they just blow the hot air from the ceiling down. I am wondering if elastomeric paint can be applied to the underside of the aluminum to help cut down on the radiated heat. Or is it only effective as a reflective covering applied on the topside of the roof. Also, is there any type of spray insulation that could be used on the underside that could help cool the area down? I am worried about developing leaks if someone walked on the roof to paint due to it's age. I would greatly appreciate your thoughts and and ideas on the problem. Thank you!

    You can add some radiant barrier foil to the ceiling of the porch, to help block 97% of the radiant heat from the ceiling from emitting off the ceiling and into the space below. That will make a good difference. Then, you can also add the foil to the walls of the area - this has to be done in a way that the foil has an air gap, so it could require that you add some wooden furring strips to the top of the wall and bottom that the foil can be stapled to. If you choose this method of install, you can use a foil with a white vinyl backing, so the foil faces the wall with the foil open to the air space created by the furring strip and the white vinyl faces the porch area, where it looks nicer than a shiny silvery foil would. See the product here: http://www.atticfoil.com/products/48-wide-foil-white-vinyl-perforated.html

  67. Rating: +0

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    Here's to hoping you still read/reply to these. I am replacing siding on my house and am debating between plywood/quietbrace with perforated radiant barrier (plus 3/4" air gap) vs foilfaced OSB (techshield) vs foil faced rigid foam (r-matte). Also, for the air gap, I'm worried about using plain furring strips (untreated wood). Should I use 4" wide foam strips, ripped 4" wide pressure treated plywood, or maybe 4" wide treated deck boards?

    Furring strips will work just fine, so would any of the other options you listed. Techshield is probably your best "bang for the buck" in terms of performance and cost.

  68. Rating: +0

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    I have a company trying to sell me a radiant barrier "40lb.,.29mm commercial grade 2 ply radiant barrier foil" They say they have a patient for the next five years and nobody else can sell this product. internet search got no hits on this product. Does such a product exhist. thanks Joe Marquette

    At some point weight gives no additional benefit and in fact makes it harder to install. We sell millions of feet each year and the customer feedback speaks for itself. I recommend you get a FREE SAMPLE of our product so you can "try before you buy," if you have not already. Request the sample here: http://www.atticfoil.com/free-samples.html

  69. Rating: +0

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    My husband had radiant barrier and two fans in our attic in phoenix. It was installed we didn't do it. In phx in the summer is very dry but the humidity in the winter can get much higher. Our first winter with the radiant barrier (this winter) and my wood floors feel very sticky, shows every little print and looks almost like there is a film. Nothing else had changed in our home. Can the radiant barrier keep humidity in the house?

    It's not likely since it's so far from the area in question. The radiant barrier installed should also have been perforated, so if it was, then it would be able to let moisture pass through to air out. Again, based on where the barrier was placed and what type of radiant barrier was used, it would have little to no effect on this.

  70. Rating: +0

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    Is there a difference between Silvertanium and Attic Foil radiant barriers? Also, I am preparing to install a metal roof over an existing composit shingle roof using a radiant barrier and furring strips between the shingles and metal roof. Do I need to be concerned about venting the air space between the radiant barrier and the metal roof?

    Yes, the Reach Barrier (Silvertanium) is a METALIZED FILM but AtticFoil is a pure aluminum radiant barrier with a 97% reflectivity - it is a different material altogether. I actually used to sell metalized film (like Silvertanium) but stopped selling it because (1) it didn't sell well, (2) installers didn't like working with the material - it was harder to work with than the aluminum and (3) it had several instances of issues with delamination and oxidation, despite the claims that those were not an issue/problem. For more info on the oxidation issue, take a look at this page on the AtticFoil website: http://www.atticfoil.com/faq/80-faq/283-metalized-radiant-barrier-film-oxidation.html

  71. Rating: +0

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    I live in central New Jersey. I am considering a perforated version of your radiant barrier. My concern is during the winter? Will my attic trap moisture in cold season because the attic does get cold and my fear is the perforation will form ice and thus not allow flow of air. Is that a possibility? Any way to avoid it? Also, radiant barrier can keep an attic cool during a hot summer, but will it reduce heat in the attic in winter? Would that lead to higher heating bills in winter? Again I am in New Jersey so not sure if folks in my climate zone should not consider radiant barriers. Any advise will be greatly appreciated.

    The only way your attic will "trap moisture" in the winter is if there is no ventilation. The foil should be laid on top of your insulation in the winter to stop the air transfer between the cold attic air and the warm air leaving the insulation/house. Watch this video to see it explained in detail: AtticFoil Radiant Barrier Over Insulation for Cold Climates.
    So, install the foil on top of the insulation, just like the site instructs (pay attention to the warnings at the bottom of that installation page) and then make sure your attic is well vented to keep things DRY.

  72. Rating: +0

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    Wish I would have found your website before we had a barn built - I'm afraid we wasted money. Our building used single bubble foil insulation on both the ceiling and walls (right next to the metal). There does not appear to be a true gap (other than the spaces created by the ribbed metal siding). Will the spaces created by the ribbed metal be sufficient to radiate the heat back out or did we waste a ton of money of single bubble foil insulation? Thank you.

    Probably not a complete waste, but more like a probably a drop in effectiveness. It really depends on how much "open space" or "non-contact" with the foil you have.

  73. Rating: +0

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    I want to install radiant barrier on my exterior walls then vinyl siding, my question is the house already has a vapor barrier,I can not find perforated barrier in my area ,can I use non perforated barrier and leave a 1 to 2 inch gap where barrier would overlap

    No, I would not recommend using a vapor barrier out there. Where are you located? We ship all over the USA (and Canada) from AtticFoil.com so you can order a perforated foil and have it sent to your door.

  74. Rating: -1

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    how to create an airspace if im am replacing asphalt shingles

    The simplest, though maybe not most cost effective, way is to add the radiant barrier to the topside of the roof deck, then add furring strips (wooden strips) across the deck and then add a second layer of plywood to attach the shingles to. This creates the air gap needed by the foil, but still allows you to use shingles. Another option is to take OFF the deck and add foil FIRST, then put the deck back on top and re-shingle. This puts the foil open to the air space below (inside the attic) and it will work this way.

  75. Rating: +0

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    I have a cathedral ceiling. can I install the readiant barrier on the finished interior below the insulation without venting and expect a significant reduction in heat gain? The room ceiling radiates heat from the hot California sun into the room. The existing insulation is r-19 or less. The installation will reflect the heat...back up to the insulation which will retain it in the space??? i do not want ot remove the interior finish and re-insulate. I would put some kind of light weight ceiling finish over the radiant barrier with an air space.

    Can you do this? Yes. Is it the MOST effective way to add it? Not really, but if you are not wanting to remove the ceiling and start the process over then this is a good option. The foil is not going to increase the heat coming through the roof or passing through the insulation. The foil will simply prevent any of that heat from emitting into the room below, as long as you install it with the proper air gap on one side. There is no way to really trap heat - heat will always move from hot to cold; it will find a way out.

  76. Rating: +0

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    What is trhe difference between your foil and techshield? New construction and I'm lerning a lot from your site. Thanks,

    The main difference is in HOW they work - one uses emissivity and the other uses reflectivity to block heat gain. Read more here: TechShield vs AtticFoil Radiant Barrier

  77. Rating: +0

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    Hi! We are building a home that is 1/2 mile from a cell tower. Would it be helpful to have a radiant barrier on walls & roof to keep away the harmful radiation? Thank you in advance!

    The amount of RF energy from a cell tower is thousands of times less than the limits for safe exposure, so it shouldn't be an issue at all. Foil might help, but this is not the intended use for AtticFoil so I can't say to what extent it will be the solution you are seeking.

  78. Rating: +0

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    Hi again Ed. Hey, I was just browsing and it is so funny because I found a lot of my answers to my questions when I wrote you almost two years ago. I just wrote you with questions about twenty minutes ago. I'm definitely not spray foaming my ceiling and want to use fiberglass. Maybe of you could just reiterate and maybe tell me like how big of an air gap do I need between my insulation and the foil backed sheathing and if condensation is a possibility. There are can lights but are supposedly sealed and I will be sealing any gaps around drywall and cans, where they meet. Sorry, I had forgotten you wrote. Maybe you can just shoot me an email I you don't want to post my new questions. Thanks, Nick

    In a cathedral ceiling you want at least a 1/2" or 3/4" air gap between one side of the foil and any other material, even insulation.

  79. Rating: +0

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    finishing my attic to livable space, planned to use Styrofoam channels then r-19 fiberglass insulation, but in NC so felt the radiant barrier would be good to reflect more heat with the fiberglass insulation together...so, question, can enerflex panels be used first (creating a 3' air channel) then adding r-19 fiberglass next? I am trying to determine if the enerflex panels give me a advantage being both the radiant barrier and air channel, otherwise, I would have to do spacers, a radiant barrier, then the fiberglass...trying to do 2 steps vs 3, thoughts?

    In this case the Enerflex could offer you the benefit of air channels and radiant barrier, but they also take up a LOT of space in the rafter cavity, so you don't have much room for the R-value fiberglass. It may not be the answer you wanted to hear, but you'd be better off using spacers, radiant barrier and then having room to add your fiberglass on top.

  80. Rating: +0

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    Greetings Guru! I have read (on the spec sheet for Reflectix) that one can achieve close to R20 in a crawl space by lining the whole cavity with a radiant barrier. I don't have a crawl space but a 40' triangular shotgun attic with a 24' width and a 13.5' apex. I am considering this: lining the roof rafters 2" Tuff-R (R13), mounting 2x2's on top of that, and finally mounting 1/2" plywood (cause I like wood grain walls) on top of the 2x2s. Here's the question: if I glue a layer of attic foil on the inside of the plywood I will have created a 1.5" airspace lined with radiant barriers. Am I right in thinking that this will achieve the type of R value gained by lining a crawl space in radiant barrier? -Josh B.

    Whatever the collective R-value of the materials you use in your construction amount to will be the r-value you have. Radiant barrier does not have an r-value on its own; read more about that here: R-value for Radiant Barrier?

  81. Rating: +0

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    Is radiant barrier roof sheathing waterproof?

    Liquid water won't pass through the perforated foil, but water vapor molecules (water in air) can. Neither liquid water nor water vapor can pass through the solid foil.

  82. Rating: +0

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    My contractor is suggesting I put the radiant barrier in my tv room to help on noise control will this have much effect

    Radiant barrier has been used in SCIFs to both block EMF signals and to help with sound proofing, but it is usually used in conjunction with other materials. I suggest you look in to some other options if you need soundproofing; spray foam, foam board or traditional batt insulation would probably provide that benefit better than just a layer of aluminum radiant barrier.

  83. Rating: +0

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    I have a Derksen Portable Building that we are turning into our home. We have installed the radiant barrier as you demonstrated in the cathedral ceiling video, but my issue is that the rafters are 2x6 and that doesn't leave room for the correct R value of traditional insulation the only one that seems to fit correctly is R13. My question is will the radiant barrier and R13 be sufficient or do I have any other option. I live in North East Texas.

    If you are under code to fit a certain R value, then the only option you have is to add depth to the wall cavity so you can fit it in there. The foil has no R-value, since it is a radiant barrier and not a conductive heat barrier; it will allow the R-value material to perform more optimally and closer to its true R-value, but in terms of actual R-value, it adds none.

  84. Rating: +0

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    I would like to know if a bubble wrap-foil radiant barrier function well when directly attached to galvanize iron metal roof in hot climate.If so, should the bubble wrap side be attached to the roof while the foil side facing the empty space below? Would it be better if I use a double foil instead of one sided foil? What bubble size wrap should I choose for this type of radiant barrier insulation configuration? Thank you.

    Bubble foil works, but why pay 4 times the money for the same benefit as a regular radiant barrier? The foil is doing all the reflecting of the radiant heat and the bubbles are usually just along for the ride. For a metal roof over a residence, I'd attach the foil along the bottom side of the rafters (as usual) and leave a nice big air gap between the underside of the roof and the foil. If it's for a metal building - then the same application would apply. Check out the installation guides for commercial applications on my new site: www.WareHouseFoil.com

  85. Rating: +0

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    Is Radiant Barrier effective on the firewalls in a townhome attic?

    For a radiant barrier to be effective at blocking radiant heat, it needs to have a radiant heat source and an air gap on at least one side (doesn't matter if the air gap is on the same side as the heat source or the opposite side).

  86. Rating: +0

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    I live in Tx near the coast in a rv, I am curious to know if there is a product that could be rolled out over rv and removed when not needed or windy tks.

    To my knowledge there isn't a pre-fabricated product like this, but I know of several people who've made similar prototypes with good results.

  87. Rating: +0

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    I believe the site answered my concern, but we just had our roof redone, the contractor suggested the low e insulation. We have a flat roof, and we are suspecting the low e was not installed correctly. The house is warmer than ever and fails to cool even when temperatures are not as hot. Is there a manual, installation guide, someone who could tell us if the sheets were not installed correctly? I am almost positive they were not. We appreciate the help.

    It's pretty simple - if the sheets are not open to an air gap/space, then they're not performing as a radiant barrier. When foil is touched/sandwiched on both sides it is a CONDUCTOR, not a radiant barrier/reflector. So if the low-e was just layered on and covered up, it's offering zero benefit toward stopping radiant heat.

  88. Rating: +0

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    I have a 30' X 40" metal shop building, it is insulated with "bubble wrap". I am trying to cool the shop with a 28,500 BTU window unit, that does pretty well until it gets really hot. I was wondering if adding another layer of bubble wrap insulation to the bottom side of the roof supports would be beneficial, or cause a problem.

    Adding another layer of the same product right below the first layer will offer little to no added benefit. It definitely won't justify the cost for the additional material!

  89. Rating: +0

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    I have a stock of EPs 4" iso board. I have tore all drywall out of my house and was thinking of how I could properly layer radiant barrier with the 4" board to get the best results. Also I'm concerned with moisture and any effects the EPs may create. Thanks so much..from central Florida

    If you're doing the inside of exterior walls, you'd want the foil closest to the outside. This page details an excellent way to build out a wall using foil radiant barrier and foam board: https://goo.gl/v6FjjI

  90. Rating: +0

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    I have removed the walls in my bedrooms down to the studs, exterior sheathing is visible. I want to install a radiant barrier between the studs next to the exterior sheathing. House is oriented to where it is in full sun for at least six hours per day. I cannot remove the exterior siding. Is it possible and what material would you recommend. Thanks

    With the space gutted you're in the perfect position to add radiant barrier to the walls. Complete install instructions are on this page: http://www.atticfoil.com/applications-a-uses/walls/outside.html

  91. Rating: +0

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    is radiant barrier foil the same as radiant thermo insulation with foam in between foil? my understanding is the foam acts as a a air space so that when it is installed between the single and felt, it becomes an effective radiant heat barrier.

    In both products the FOIL is doing the work to block radiant heat transfer.
    Note: Foam is not an air space, foam takes up space - it has mass. An air space must be just that: a space filled only by AIR. otherwise the foil will not work.

  92. Rating: +0

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    I have a stock of EPs 4" iso board. I have tore all drywall out of my house and was thinking of how I could properly layer radiant barrier with the 4" board to get the best results. Also I'm concerned with moisture and any effects the EPs may create. Thanks so much..from central Florida

    This is a pretty common installation - you can see how to properly layer the materials here: https://goo.gl/v6FjjI

  93. Rating: +0

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    I have seen cabins and rooms walled with shiny corrugated roofing metal. Does this work as a radiant barrier to keep heat/cool in? How about moisture problems? Thanks

    The roof itself is not likely 100% pure aluminum (i.e. it’s an aluminum alloy); therefore the roof is more like a shiny bumper on a car - it’s HOT no matter which side you’re on. If you go with perforated radiant barrier foil, you won't trap moisture since the foil breathes and allows moisture in vapor form to pass through to dry out.

  94. Rating: +0

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    I HAVE HEARD BEFORE THAT IF YOU USE A FOIL RADIANT BARRIER IT WILL TRANSFER THE HEAT UPWARD AND AWAY FROM YOUR ATTIC SPACE....BUT....ALL THAT HEAT COMING DOWN THRU YOUR SHINGLES AND THEN BEING TRANSFERRED RIGHT BACK UP THRU THE SHINGLES AGAIN WILL OVERHEAT THE SHINGLES AND "BURN THEM UP" ......DECREASING THE LIFE OF THE SHINGLES. IS THIS TRUE?

    No, it's not true. I explain the science behind how radiant barrier works & show you roof temp readings here to prove it: Does Radiant Barrier Foil Damage Roof Shingles?

  95. Rating: +0

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    We paid $13000 to have a radiant barrier put in our 3000sf home. I know now that we got skanked. The barrier stops about 4 ft from the eave and the ridge vent is sealed. They sprayed the 9 inches of insulation with the pump in the truck like you warned in one of your videos. Anxious to see how it settles. Do we need to add more to the barrie eave? or is this adequate? Do we need to open the ridge vent? Why didn't we find you before we did this.?

    Depending how high the roof is, 4 ft may not be all that bad (still it's a shoddy install for $13,000 no doubt), most people that DIY get closer - about 6" from the ridge and eaves. I'd get a probe thermometer up there and measure some air temperatures. If you have good airflow the air under the foil should read within 10 degrees of ambient. I'd definitely recommend having any vents opened and unobstructed to maintain proper airflow which does help temp, but more importantly helps keep the attic dry and moisture from accumulating.

  96. Rating: +0

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    I am sure that I want a radiant barrier on the underside of my roof rafters but need a couple of questions answered. I have a home built in 1941 near Evansville IN, with 2"x6" roof rafters at 24" OC, and it now has a metal roof. There is also approx. 12"-14" of blown-in on the 2x6 ceiling which is at 16" OC. 1. Would you go with a bubble-sandwiched between 2 radient barrier layers (and if so would that help with the sound transmision) or go with an extra tough non bubble product? 2. Would you go with a perforated or a non-perforated product? Much thanks

    1. No, I would never recommend bubble-foil in a residential attic application.
    2. In an attic you should always choose perforated. Which is probably the #1 reason you shouldn't use bubble foil in a residential attic - it's a vapor barrier.

  97. Rating: +0

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    Just had radiant shield installed. It's October and 60degrees outside and my house is hot as hell. I have to keep the AC on. Please help!!!

    Working on the assumption that the radiant barrier was installed CORRECTLY, you may be experiencing what is known as The Spring/Fall effect: http://www.radiantbarrierguru.com/the-spring-fall-effect-can-radiant-barrier-work-against-you/

  98. Rating: +0

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    I live in St. Louis MO and would like your input on how to properly apply a radiant barrier to my home. I have attic space running down the front and rear of my entire 2nd floor and another attic above the 2nd floor. The front and back attics connect to the upper attic via the roof rafters. The interior ceiling height is 8' but the wall height is only 6' there is drywall at a 45 degree angle is attached to the roof rafters on that 45 degree angle. This is the space that connects the attics.The floor dimension front to back is 14 feet and the roof dimension is 10. (sorry for the lengthy word picture) I want to install a radiant barrier to the underside of the rafters and I'm not sure how to go about it given this connection between the attics. Also do you recommend adding radiant barrier to the backsides of the interior walls in the attic space, currently there are paper faced insulation batts in there with the paper facing the room. Thanks

    just staple the AtticFoil to the rafters (this allows air flow between the foil layer and the roof deck up to the ridge) so that air flows normally, as if the foil wasn't there and you'll be all set. For more information on leaving gaps in the installation for proper air movement, see this video on our website:

    Proper Gaps for Airflow When Installing Radiant Barrier

    And yes, you should add foil to the knee walls of those rooms, especially if you can't get it on the slope of the roof next to those rooms. Details here: How to Install AtticFoil on Kneewalls

  99. Rating: +0

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    I am wanting to keep the heat down in my attic and i began installing bubble wrap type radiant barrier just below my galvanized roof. I then put insulation below it. Since it is not perforated, will i have moisture issues? My ventilation is through the ridges all the way down both sides of my house coming from the ridge vent up top. I need to know before continuining my install. Thank you. Paul

    Paul,
    Bubble foil used in residential applications can result in issues with trapping moisture. I can't say for sure how the product will affect your home - there are several variables at play in this scenario. Your best chance is to get plenty of unobstructed ventilation in and around the foil, so the area can easily dry out if moisture does form.

  100. Rating: +0

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    I have just heard of a product called superglo. It is foam insulation with the radiant barrier on both sides. I have a vaulted ceiling with 2x6 rafters, a ridge vent and was wondering if this is a good way to go?

    That could work as long as the foil side is facing an air gap (and ideally closest to the roof). As far as cost and ease of installation go though, you might consider the standard cathedral ceiling method shown here: Installing Radiant Barrier in a Cathedral Ceiling.

  101. Rating: +0

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    Hi Ed. Could you tell me if TechShield has any R value rating ? Thanks, BP

    Radiant barrier on its own has no r-value. I can't find where LP publishes a claimed r-value for their Techshield.

  102. Rating: +0

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    Ed, First, thank you in advance for your help!! I have a 22 X 21 metal building that is basically a garage. I live in Georgetown TX, and was wondering if I use the aluminum Radiant Barrier on the walls and roof, would I benefit further if I then have Foam Insulation sprayed over that?? OR ... would one or the other be better to use by them selves. I've never used either of these systems before. Thanks again!! Michael

    On non conditioned spaces like garages, there is nothing better to temper the heat gain that a radiant barrier. These structures will greatly benefit from the addition of our foil on any, and all, sides that catch direct sunlight - so the space above the garage, the garage door, & the garage walls. Furthermore, since it's not conditioned, you don't really need to have regular or foam insulation in there (that's why they are built without insulation), just the radiant barrier.
    Check out www.WareHouseFoil.com for install videos and photos of buildings like this with radiant barrier installed.

  103. Rating: +0

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    Can I install radiant barrier against sheetrock, then lay batt insulation?

    The radiant barrier WILL NOT WORK unless at least one side is facing an air space. Sandwiching it between insulation and sheetrock will not give it the air space it needs in order to work properly. This page shows how it must be done when installing inside a wall: http://www.atticfoil.com/index.php/applications/inside-exterior-walls-hotmixed-climates/

  104. Rating: +0

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    Hello, I have a techshield roof. Recently our area suffered a sever hail storm and my insurance company is paying to have new shingles installed. My concern is that all the original nails holding down the original shingles will be removed leaving holes in the roof decking and the techshield. And, new nails will puncture the techshield for the reproofing. How will this compromise my radiant barrier? Is new roof decking with new techshield in order? Thank you Edward Sonnen

    It's not going to be a big deal - no need to replace the TechShield.

  105. Rating: +0

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    Will a radiant barrier ( like Reflectix) lower EMF radiation if wrapped around a bundle of wiring? This wiring runs right under our babies room floor.

    EMF is way out of my area of expertise, so I can't comment on if/how well it would work. You could try reaching out to the manufacturer to see if they have any further insight.

  106. Rating: +0

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    Is radiant barrier attached to the underside of my rafters effective? Approx. how much should I expect to pay for this type of installation? I live in Dallas, Texas so you can imagine why I am interested.

    It is - in fact it's proven to be the most effective place to put a radiant barrier in a home! You can see the test results here:
    As far as the cost - that's not so cut and dry. I've known of installers charging as little at $0.25/sq ft installed and others charging upwards of $3/sq ft. Really, if you can DIY or hire a handyman or someone like that, this is not an expensive job. I supply foil to several companies in DFW - check out the website and find one near you and ask them for a quote - that's probably the best way to get an idea. Find an installer here: https://goo.gl/cBd2bK

  107. Rating: +0

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    Is it ok to use 15lb felt paper as a radiant barrier above the insulation in my crawl space?

    Felt paper is not radiant barrier, so it will offer you no benefit toward stopping radiant heat gain/loss.

  108. Rating: +0

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    I recently had my shake roof replaced with a new composite roof on my home in California. At first my contractor was going to install radiant barrier OSB, and to create the required 3/4" airspace, he was going to add additional wood strips. Later, after some concern with total cost of the project, we agreed to use regular OSB decking and add extra blown-in insulation to bring up to R38 value, to meet Title 24 requirements. Due to some mix up between the contractor and supplier, I ended up with Roy O Martin radiant OSB at the same price as regular OSB. I have two questions. First, when I go in to my garage and look up, I see nails coming through the radiant OSB. Does this affect the performance of the radiant barrier? Second, since the radiant barrier OSB was nailed directly to the wood strips that previously held the old wood shakes, with no additional wood added to create the needed 3/4" air space, is the radiant OSB going to make the interior of my home hotter? My contractor said it is good to have the radiant barrier OSB even without the 3/4" airspace required for Title 24 compliance.

    1. No, the nails aren't affecting how the radiant barrier works.
    2. As long as you can SEE the radiant barrier above you, then that means it's using the ATTIC as the air space it requires to work. I cover this application extensively on this page: http://www.atticfoil.com/technical-information/dept-of-energy-test-results.html

  109. Rating: +0

    Positive Negative

    The basement of my home is not heated. It contains a water heater and a furnace. In the winter the basement is quite warm due to the heat coming off of the hot water pipes. In order to save energy I would like to insulate the pipes. Some of the pipes are very close to other pipes, and to the ceiling, or the walls, so I am looking for a a insulation material that is relatively thin and can be wrapped around the pipes. I have found a six inch wide single bubble-double foil pipe wrap (radiant barrier). Would this product be a good choice for this application, and would this achieve an R-value of about 4. Thank you

    If the foil is facing out toward the surround air, then it will use emissivity to prevent some of the radiant heat loss. I would check with the manufacturer of the bubble foil to make sure they recommend using the foil in this way. Gas furnaces are usually unsafe to cover with radiant barrier. As for the R-value, read the fine print because advertised R-value are usually not valid for normal applications; the fine print may suggest very specific conditions in order for the R-value to reach 4 and it typically includes a sealed box/air space, which would not be the case of the basement.

  110. Rating: +0

    Positive Negative

    I just purchased a wooden garden shed. The ceiling is the foil side of the the Radiant Barrier. I am painting the interior of the shed white. Can I paint the foil side of the Radiant Barrier white also, or will paint damage it?

    If you paint over the radiant barrier it will no longer be effective, it must be open to air. If the shiny foil side is covered with anything, then you no longer have a radiant barrier to block the heat from coming in via the ceiling.

  111. Rating: +0

    Positive Negative

    I want to sheet rock my shop ceiling so my wood stove is more efficient in the winter. But equally so in the summer, I want it cooler. My question is can I install Radiant Barrier first to the ceiling joist, then rock over it for a easier install? Thank you Larry

    Yes, you can do this. As long as the FOIL/shiny side is open to an air space, then this will work. The video on this page shows you how to do the install: https://www.youtube.com/watch?v=85S4F_2z5nM

  112. Rating: +0

    Positive Negative

    I live in California and need to be title 24 compliant which is have a R38 rating. I also have wood shake with 1x4 skip sheeting, can I install 7/16 Tech Shield on top of skip sheeting?

    Because of the close spacing on skip sheeting, you're really not going to get much benefit out of Techshield. The radiant barrier layer is going to offer you MUCH MORE benefit if you staple it up across the rafters in the attic. As far as Title 24 Compliance, the rafter method would meet that.

  113. Rating: +0

    Positive Negative

    Hi, I saw your comments regarding a Radiant Barrier below a radiant heat system that has the hot water tubing installed below a subfloor, but what about when it installed in a slab above the subfloor in a 2nd story? Of course, if unconditioned space is below, it seems like a radiant barrier with proper air space would make sense, but what about if the space below is conditioned space with a slab on grade radiant system? To save money, I don't want to insulate between the 1st and 2nd floors of my new home, but was considering a radiant barrier to mitigate heat migration from the slab on the 2nd floor downward, which could cause the 1st floor to be overheated. Is this something I should consider, or a waste of time and money? If it is a good idea, can I staple the radiant barrier to the bottom of the floor joist with 12" of air space, or does it need to be up in the bay 1-1.5" below the subfloor? Not having to cut the barrier to staple up inside the bays would save a large amount of time and some material, but wasn't sure the effect this would have? Thanks.

    Yes, you can use the foil between floors to help direct radiant heat a certain direction; remember, the foil works both ways! To do this, you would ideally have the foil closer to the radiant heat source, in between each joist. To save on cutting each piece, you can measure the distance between joists and buy a remade roll in that size, or cut a 48" wide roll down to the width you need. 12" of space is ok, but you'll have a lot of the radiant heat just heating up that air, and not really working most efficiently to keep a space warm.

  114. Rating: +0

    Positive Negative

    Thank you very much for your great website. I have a new home with cellulose insulation in the floor of the attic. The attic is not going to be used for living or storage. Unfortunately, we have all of the duct work for the second floor of our home in the attic, along with two air handlers. I now this is a no no - much better to insulate the outer perimeter - but my wife is severely asthmatic and we had few options (worried about foam, etc.). We recently found a product called "Supper Attic" that uses "Silver glo." It is a sandwich of radiant barriers and foam board insulation in the middle. It looks attractive, but I need to "ignition proof" the underside facing the attic. Do you have any suggestions? Our home is a large modular home and the truss structure in the attic makes getting sheet rock, etc. hard to get up there. Second question. Are you familiar with the McDowell Ownens report on the risks of radiant barriers in an attic? They claim it can literally attract lightening and be a fire barrier. This concerns me, so I would like your opinion. Thank you very much.

    I don't know what you mean by "ignition proof" - who is saying you need to do this? I would ask them for clarification.
    As far as foil/foam board products, they do work, but really it's the FOIL that's doing the work. For a fraction of the cost, you can get the same results using a foil sheet product like AtticFoil Radiant Barrier.
    About the lightening scares, we've seen the article before and this question comes up every so often. The reality is that if lightening strikes your home, your problems will be bigger than the foil and the whole house will be a fire hazard since it is framed in wood. Just as wrapping a tree with foil wouldn't change the outcome if it were to be struck by lightening, the same is true of your attic. More than 9 times out of 10 these problems you read about are either due to error on the part of whomever installed it OR it's just plain bad luck (in the instance of a lightening strike) and not bad foil.

  115. Rating: +0

    Positive Negative

    I am planning my insulation install in a cathedral ceiling near Kansas City, Mo. House is 1984 2x4 wall ranch, 4 12 pitch roof. I have taken out load bearing wall and installed ridge beam, opened the center of the house up. I added furring strips to the 2x6 rafters and am now looking to insulate. I also installed cross ties approx 14" down from peak to create a narrow flat surface for the peak of the ceiling. My thoughts are to install venting baffles from soffit to ridge in each bay. next, a radiant barrier (single sheet, no bubbles) in the bay and then high density batts. 1x4 purlins perpecdular to rafters with 3/4" rigid foam between purlins. Corrugated tin for the finished interior ceiling. I know I am under the recommended R factor for this part of the country and am trying to get as much out of the depth I have. BTW, I will have a wood stove in the house as well. Central air and heat as back up also. My concerns are Is the radiant barrier necessary (I am worried about heat gain in the summer with will the air baffle interfere with the performance of radiant barrier (I want to make sure the air is moving as needed) Am I on the right track? Would you do anything differently? Many thanks

    If you're using the baffles, then you should put the radiant barrier FIRST, right on the roof decking underside. That way only the edges of the baffle will touch the foil, so the rest of the surface area of the foil will work to prevent radiant heat from entering the cavity. Otherwise, follow the steps on how to install the foil on this page, it doesn't use baffles, but it does create an air channel for air flow; we've had hundreds of people use this method with very successful results: http://www.atticfoil.com/applications-a-uses/cathedral-ceilings/foil-to-outside.html

  116. Rating: +1

    Positive Negative

    Iam slowly building a small cabin with my son...as we both are quite new at this. Due to severe chemical sensitivity, I am building this as non-toxic as i can afford. So, I am not going to insulate. My ceiling is 2x8 16" center. Can i put the foil directly under the rafters then put my ceiling mateial on that? Enough air space for hot sun in, will it keep the cabin warmer as well. And if I do it that way, do I use perforated or solid? We have a non-vented metal roof. Thank you for your help.

    Yes, the foil will work to stop heat transfer as long as there is an air gap/space on one side of the foil. This air gaps allows the foil to stop 97% of radiant heat from coming in (during summer) AND 97% of radiant heat from leaving (in winter). I always recommend some regular insulation for a conditioned space, but even if you chose to omit it because of your condition, the foil would still be useful. In this type of application, go with the perforated material so any moisture that may exist around the foil can easily pass the foil layer and (hopefully) dry out.