Radiant Barrier – Great for Hot Attic

Is a Radiant Barrier Right for Your Home?

Radiant barrier is a great addition to attic insulation. Properly insulating your home is a great way to improve energy efficiency and comfort especially if you add a attic stairs cover. With all the different products available how do you know which is right for you? Here is some information to help you decide if installing a radiant barrier is a good idea for your home.

“Remember, with all properly installed insulation, the payback is certain…if you give it enough time. If you are moving in a year, only go with the basics that will improve the sale of your home.”

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What is Radiant Barrier?

Radiant barriers are made of aluminum and designed to reflect radiant heat from the sun. When installed properly, radiant barriers can reflect up to 95% of the radiant heat off the attic. The best way I have seen to describe this effect is it’s like putting your home or office under a shade tree.

“Installing a radiant barrier is like putting a shade tree over your attic.”

There are many brands of radiant barrier available. Here are some tips to make sure you are using a good product:

Non-laminated radiant barrier – In a lamination process, the foil is either simply glued on or heat laminated to the plastic lining.  Both of these processes will eventually fail.  With some products you can peel the foil off the plastic right out of the box, with others you have to leave it in the attic for several years before you can easily peel it off.

Protective coating installed – Without this protection, aluminum will oxidize loosing its ability to reflect heat.  As the surface of the foil begins to oxidize, it turns cloudy.  If it continues and oxidizes all the way through, it will eventually turn clear.

Passes newest fire codes – make sure the radiant barrier passes all of the current codes including the ASTM E84 fire test under the new mounting method (ASTM 2599).

Radiant barrier benefits

The benefits of radiant barriers are both monetary as well as increased comfort. If your home or office are in the direct sun your roof radiates solar-generated heat to the insulation below it. The insulation absorbs the heat and gradually transfers it to the material it touches, principally, the drywall ceiling. This heat transfer makes your home less comfortable and can cause your air conditioner to run longer and consume more energy. A properly installed radiant barrier can block 95 percent of the heat radiated down by the roof so it can’t reach the insulation.

Roof-radiated heat also warms ductwork or mechanical equipment (air handler) found in your attic. The proportion of the total heat gain the ductwork represents, compared to heat gain to the interior of the house, varies depending on the amount of attic and duct insulation you have.

Should I apply radiant barrier to the attic floor?

According to the Department of Energy installing radiant barrier on the floor of the attic can cause problems. It may be an easier way to install radiant barrier but it can trap moisture between itself and the attic floor and cause the insulation to become damp. Damp Insulation may support mold growth and eventually will lose some of its R Value. If you decide to apply a radiant barrier to the floor of your attic make sure you air seal the attic floor with a closed cell spray foam prior to installation.

Will a radiant barrier damage my shingles?

I have had this question asked many times and I see no evidence that a radiant barrier damages shingles. The Florida Solar Energy Center has measured the temperatures of roof shingles above attic radiant barriers on hot, sunny summer days. Depending on the color of the shingles, their peak temperatures are only 2-5° F higher than the temperature of shingles under the same conditions without a radiant barrier. Since roofing materials are manufactured to withstand the high temperatures to which they are frequently exposed. A 2-5° F increase in peak temperatures that normally reach 160-190° F should have no adverse affect.

Radiant Barrier Cost

Since all buildings and there uses are different, this is a very difficult question to answer but according to research done by the Florida Solar Energy Center, you could save between 8-12% on annual cooling costs. If this is true, the cost of installing a radiant barrier is irrelevant given you stay in your home long enough to recoup your investment. The benefits of a radiant barrier extend beyond monetary and should make your building more comfortable as well. It is also a good idea to make sure the attic is properly ventilated. Installing a solar attic fan is a great way to save money and may qualify for a 30% tax credit.

21 thoughts on “Radiant Barrier – Great for Hot Attic”

  1. Larry Phillips

    Can U Use Inch & Half White Insulation Board First Then Radiant Barrier. To Insulate The Attic Rafters. I Have 3 Eve Vents In My House.So I Was Going To Use Them For The Vents. So The Hot Air Can Go out

    1. Hi Larry, it sounds like what your saying will work, just make sure there is an air gap between radiant barrier and insulation so the radiant barrier performs better.

  2. I’m at the begging stages of cooling my hot attic = hot house, what would you recommend (example: ridge vent, radiant barrier, attic fan) and in what order to install first?

    1. Hi Henry, Congratulations on tackling your attic. My attic had none of the items you mentioned so I started with a ridge vent and made sure I had baffles installed to allow soffit air to be pulled into the attic. If the soffits are clogged it will try to pull from living space or gable but not all homes have gable vents. Then I did the solar attic fan. The fan actually uses the ridge to ventilate properly along with soffit. Then radiant barrier but I’d also air seal as much of floor as you can especially if you have recessed lights or a drafty attic access. Hope that helps and thank you for being a DIY Ninja.

  3. Hi my question is why would you install a radient barrier under shingles or any other material that is supposed to protect your roof. Other than a metal roof that is already highly reflective given you choose a light color. My understanding is you wanna reflect the sun’s uv and ir rays from being absorbed by your roof. The radient barrier is underneath shingles so it’s being shaded and if it were to reflect any light rays they would be reflected back to the bottom of the shingles. Wouldn’t it be better to have a reflective roofing material that is exposed to the sun’s light directly?

    1. Hello Ryan. Installing radiant barrier under the roof decking is the preferred method versus on top of the insulation because it gives an air gap for the heat to escape to the ridge vent without creating a potential moisture problem between the radiant barrier and the attic floor. Radiant barrier should always be installed to work with the soffit and ridge vents. A reflective material on the roof may be effective but we honestly don’t have an opinion about it because that would be more of a roofing company product I would guess. For people needing a roof and wanting to install the material you mention, I think that sounds like a viable option. Radiant barrier is a way to get heat out of the attic for those of us that have a 25 to 30 year roof and are not looking to replace the roofing materials. Please feel free to share the reflective materials you are writing about in case any of our readers are interested. Thanks for the question.

  4. Hello! Thank you for sharing your knowledge and expertise on radiant barriers. Have a quick question about the crawl space in between the first and second floor. Should I install Radiant Barrier across the 16 in gap ? I have a very hot garage attic that has no barrier or insulation to separate the attic from the crawl space between 1st and 2nd floor. How would i make the crawl space cooler?

  5. Thank you for all of the videos and resources.
    I am currently installing a radiant barrier in my attic. I have installed below the rafters and up to the the same height as the attic vents. Should I install the barrier above the attic vents as well (another 1-2 feet), all the way to the apex of the rafters, or would that simply trap the heat at the top with no way to escape?

    1. Hello Martin, it is recommended to leave minimum of 2-inch clearance around all flue pipes, exhausts, roof vents or active air vents. I’d leave a little more, minimum 12 inches. Great question. Hope that helps.

  6. Hi Michael – Love your videos – they are EXTREMELY helpful in dealing with our crawl space issues. We live in upstate NY and are in the process of cleaning up the crawl space to do encapsulation. We would like to stay away from insulating the walls with any foam insulation to reduce outgassing in our home so we’re wondering if we could use the foil radiant insulation and if so – would that be under or over the vapor barrier? Thank you!

    1. Thank you Jim. We appreciate you watching. As long as the insulation is able to be placed in wet areas without degrading, should be fine. Also make sure R-value matches your local recommendation. We would place the vapor barrier over the insulation as long as the insulation is wet area rated. Hope that helps.

          1. Thank you. I’ve started using the batts in walls and ceilings and I really like it but just recently read about the rockwool boards.

  7. I recently had my air conditioning duct replaced under my double wide in Florida. I was told my insulation and vapor barrier were in poor shape. I have gotten two estimates to fix with two different products. One is to replace fiberglass insulation plus a vapor barrier. The second was to remove old fiberglass and just put on a heavy duty barrier. My question is do I need to do anything and if yes, with what?

    1. Our code requires a ground cover vapor barrier and sub-floor insulation if your crawl space is vented. We typically seal crawl spaces and control humidity versus allowing outside humidity to saturate sub-floor and insulation. We do this with foundation wall insulation, vapor barrier and dehumidifier. You can also check with a local codes enforcement or home inspector for guidance in your area. Hope that helps. Here is a video that could help if controlling humidity is your focus. https://youtu.be/9nCGqp63-MI

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