Installing radiant barrier in an attic

How Do I Install Radiant Barrier in My Attic?

Insulating your attic with radiant barrier provides year-round energy savings and helps cut utility bills. Installation methods vary per application, but can be boiled down to two types:

  • Installing radiant barrier directly under your attic's rafters (for energy savings in summer)
  • Installing radiant barrier on the floor of your attic (for energy savings in winter)

Many customers call in to ask which method is right for them. While both applications will work to keep radiant heat out of your home, there are certain variables that need to be considered when choosing which method is best for you.

Installing radiant barrier under your attic's rafters

Ideal for hotter climates

A large number of our customers are in the southern states and want to protect their homes from the sun's heat. If this is the case, the answer is simple. Your primary goal is to keep the heat out of your attic; therefore the best choice for installation is directly under your rafters. This is especially true if you have any HVAC units or duct work in the attic.

To maximize efficiency and extend the life of your furnace/air conditioning unit, these ducts should also be insulated with EcoFoil Big 8 duct insulation. The rafter installation is the most efficient method to keep heat out because it reflects the heat away from your attic before it can heat up the mass (e.g. fiberglass or foam) insulation below. This keeps the overall attic temperature down considerably, and reduces the chances the heat escapes into your living space. This installation method is also preferred if the attic has a functional floor and is used for storage.


Installing radiant barrier on your attic's floor

Ideal for colder climates

When installing radiant barrier on your attic floor, your primary goal is to reflect your furnace's heat back into your living space. The following scenarios are better suited for radiant barrier on your attic's floor:

  • Climates with both hot and cold extremes (midwest and northern states)
  • Steep roof pitches with peaks that are difficult to reach
  • Complicated roof truss designs

In these cases you can choose to lay the insulation on the floor of the attic. In cases of extreme climates, the foil will help minimize heat loss in the winter time.

Whichever method you choose, be sure to install EcoFoil perforated radiant barrier. These tiny perforations promote air flow, and prevent moisture buildup in any mass insulation you may already have in your attic. Attics are typically designed so that cool air enters through soffit vents and hot air exits through the ridge vent. This will also allow any humidity to escape. The following guidelines should be followed to properly install radient barrier in your attic:

  • Always use perforated radiant barrier in your attic. This will limit moisture buildup and help prevent mold and mildew from forming due to excess humidity
  • Do not overlap or tape the seams. This can trap moisture and lead to mold and mildew.
  • Allow for air flow. When installing on the floor of the attic, lay the radiant barrier perpendicular to the joists and leave a 3” gap between the sheets to allow air flow. When installing on rafters, do not cover the 6” adjacent to the ridge or soffit vents
  • Be thorough. Don’t forget to insulate the gable or knee walls
  • Maximize the benefits of radiant barrier. Many customers choose to add perforated radiant barrier in both locations (under rafters and on top of the attic floor) to take full advantage of the heat reflectivity year-round


EcoFoil attic insulation offers a 10-year manufacturer warranty, and is a popular and relatively inexpensive way to insulate your home in summer, winter, and everything in between. Our centrally located warehouses allow us to ship to the east and west coast of the U.S. within four business days, so you can keep your projects running on time. For more information on the benefits of radiant barrier in your attic, view our attic insulation page. If you have more questions or would like to insulation advice, call us at 888-349-6264, send us a chat, or send us an email. We'd be glad to help!

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