Radiant Barrier Installation Summary – Block the Heat

The one question I probably get asked most often is: “What all do I need to know to install AtticFoil Radiant Barrier Foil Insulation?”

The big concept is you’re trying to get a piece of radiant barrier foil between the roof and the insulation; the goal for heat rejection in the summer being to keep attic insulation cooler by preventing it from absorbing radiant heat from the roof. In this video I will explain it as quickly and concisely as I can.

So, in summary here is what you need to focus on:

  • Get the foil between the insulation and the roof line.
  • Staple it up across the rafters; it doesn’t have to be smooth or pretty. You can use 48″ wide radiant barrier foil to work horizontally, or 26″ wide radiant barrier foil to work vertically.
  • The staples are standard size – 1/4 or 5/16th size work fine.
  • Cover as much as possible; the more space you can cover, the better your results. Even partial coverage works!
  • Allow ventilation a free path to flow in to the attic from down low at the soffits and escape the attic up high, near the ridge (via a ridge vent, gable vent, attic fan, etc.).

If you would like to see some photos of finished installs, I recommend you take a look at these Do-It-Yourself radiant barrier foil installation photos.

Still have questions? Leave me a comment below!

24 thoughts on “Radiant Barrier Installation Summary – Block the Heat

  1. Does the radiant barrier have any effect in WINTER to keep the HEAT IN? Or is that the job of the foam or fiberglass on the attic floor? In this case, the attic floor is insulated, and a radiant barrier will be stapled to the rafters underneath the roof deck (no other insulation on rafters). There will also be an attic fan. Thanks in advance

    1. Yes, foil does offer a benefit in the winter. Basically whatever direction the heat flow is coming from, the foil prevents 97% of it from passing through the foil layer, as long as it is installed with the proper air gap. Watch the video on this page to get the full information on how the foil helps the home retain heat in the winter: Radiant Barrier Foil Installation for Cold Climates

  2. Hi Ed, we are building an ICF home with a flat roof. The attic is “unvented”, with the attic height of 3ft. Trusses of 18″, with HVAC ducts and water lines in the attic. What is the best combination insulation product for us.We are building in WV.


  3. Ed,

    How much airspace, if any, is needed between the radiant foil and the roof to be effective? I had a company install mine and they installed it vertically in between the roof joists mostly right up against the roof (some of stapled right to the roof). I told them i thought that to be effective you needed several inches of airspace between the radiant barrier and the inside of the roof. Am I correct and if so, what minimum airspace is needed?

  4. I live in south east Texas and I am very interested in the benefits of a radiant barrier but I noticed you had a popup text in the video about not recommending attic fans. Question 1: My house has 2 solar powered ridge fans, will they affect the installation? Should I cut ports in the top of the foil near the roof ridge to allow the air to pass. Question 2: My roof also covers my two patios, should I use the barrier to make a “foil wall” to shield or block out the un-insulated portions over the patio? This will still allow the heat to move up the roof rafters to the roof ridge. Thanks for a great video.

    1. If you have any hole in the roof – fans included, you will want a corresponding hole in the foil to allow air to flow freely. See picture below:
      Radiant Barrier and attic fans

      For the patio, I would NOT make a “wall”. Just continue down over the patio. You will be amazed at how much cooler the ceiling of the patio will be and you can usually FEEL cooler since the ceiling is putting out less heat.

  5. Do you know this company? They had a promotion for temperguard and said it would cost 2k to do the attic 3br 2 ba 1450 sq. ft. What do you think?

    1. $2000 for 1450 sq ft. comes out to $1.37 per sq. ft. AtticFoil Radiant Barrier Foil costs only about $.13 per ft. So, you are paying about $1.25 per ft. for labor. This seems VERY high for laying out over the insulation and fairly high for the staple up method. Installing radiant barrier is not really that difficult. I would look to finding a handyman type installer or even a couple of college students to do it.

  6. If you install the radiant barrier, it seems to me that you will no longer be able to inspect if there is mold or rot. Does the radiant heat barrier do away with mold ever forming?

    1. Mold and rot are usually cause by either roof leaks or really bad attic ventilation. Installing a radiant barrier won’t prevent or fix either one.

  7. I am curious about the “dust effect.” If the radiant barrier is reflecting the rays from the roof then it would seem to need the air gap between roof deck and foil and if only one side is “shiny” then it should face the roof deck. I read on sites that the roof-facing face will become covered with dust and not work well after 1-2 yrs, so put it in with “shiny side toward the attic space.” I see you product is shiny on both sides, but isn’t the effect from the top-side shiny doing most of the work? And if so, what about the “dust effect?” and, generally, doesn’t the reflector need to face the source of radiation?

    1. There is usually not as much dust in an attic as one would think. In order for dust to land on the foil it must do TWO things. First, it has to be LIGHT enough to be drawn into the attic. Then, all of a sudden it must be HEAVY enough to fall on the foil. I’ve been in thousands of attics and unless you are next to a dirt road they aren’t real dusty. Even if the top layer DOES get dusty, the bottom layer will still be effective due to the emissivity quality of radiant barrier foil. Here is a page on the AtticFoil.com website that talks all about The Effect of Dust On A Radiant Barrier.

  8. I am wanting to do this process myself and I was wondering where you recommend buying the product from at the best price and how to accurately measure how much or how big of a roll I would need. I also saw on a homedepot site where they sold an “enerflex radiant barrier ” panels that measured 24″ x 4′ or 16″ x 4′. I was wondering if this would achieve the same outsome as the radiant barrier sheets….the panels seem similar just without having to staple…thanks so much!

    1. Stacey, we are the manufacturer and you can buy online at http://www.AtticFoil.com Enerflex works but it is several times more then AtticFoil and by putting the product between the rafters, you will get what is called “thermal bypass”. Basically, the heat will pass through the uncovered rafters and re-radiate into the attic. Stapling AtticFoil to the BOTTOM will help eliminate the thermal bypass. Plus you can pull a long/big sheet and cover a large area quickly.

  9. Hello, I am interested in installing a radiant barrier in my attic, but there are parts of the rafters that are inaccessible for various reasons. Will installing a barrier on only part of the attic still be effective? I estimate about 75% coverage.

  10. My patio cover transmits too much heat. Do you have any products that could reduce this problem. My patio cover is simply plywood with felt and a asphalt roll. If I could cut down on the radiant heat transmitted by five to ten degrees, that would be great. Thanks, Bill

    1. Yes, if you’re trying to keep heat out, the best place to put the foil is right below the roof itself. Are the rafters open to the porch? If so, you can just staple the foil across the bottom of the rafters up there. This would be a perfect scenario for our foil + white vinyl product! The foil will face up, toward the empty rafter cavities and the white side faces down, toward the covered area.

  11. We are looking at installing radiant barrier, we’ve had it before, we know it works. There are some new options, now, though and we have questions. A guy came and was obviously pushing spray-in (which we thought wasn’t a good option even if it is the best spray-in and not watered down), he said if we did the foil we’d have to get soffit vents across the front of our house (we only have them on 2 full sides & part of the 3rd side, none on the front side) in order to have proper ventilation so it didn’t decrease the life of our roof. He also said since our roof was lower they would compact all our insulation in the installation process putting down decking to work from. I’ve been googling to try to answer the ventilation question, but thought I’d ask here…

    1. Heat is heat. Even if you only covered half a roof with foil it will still reduce MORE total heat BTU’s than spraying the entire roof. As for ventilation, ideally you want air to enter the attic from as many points as possible. However, if you leave a gap at the top and bottom of the foil, the air will naturally convect and find a way out. If you have a lower pitch attic, I’d consider the “hybrid” method to Install Radiant Barrier In Low Attics.

  12. I want to make sure that my attic is energy efficient. It’s good to know that a radiant barrier can help keep the heat under control! That’s definitely something worth getting a professional to install for me.

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