The Staple-Up (also known as the Open-Ridge) method is the standard method used most often.  In this method, the radiant barrier foil is stapled on the bottom of the rafters inside the attic. During the installation you will work to leave a gap at the top and bottom of all rafters and a space is left along the ridge (peak), hips and valleys and any attic vents. The spaces and slits are created to allow for continuous air flow through the attic, as if the radiant barrier foil was not even there.

If you have a tall attic or high ridge, consider the Flat Top Installation Method. This method will keep you from having to climb ladders inside your attic. With this method, you will run the foil up the roof slopes to a height of about 7 ft. Then create a grid or a false ceiling for the foil to run across the top. You will cut some holes in the flat top part for air to flow freely through the attic. Many customers combine this method for the tall parts of the attic and use the standard staple up method for the easier to reach areas.

Benefits:

• Provides a cooler attic space
• Allows for storage on the attic floor
• Keeps air handlers, duct work, etc. in a cooler environment for more efficient systems
• Does not interfere with insulation placement 
• See Customer DIY Installation Photos

The video below is the second of a 3 part series of installing radiant barrier in an attic space. This video covers some basic tips and trips from professionals, as well as the supplies needed to complete an installation. Ed also answers the common question, "How much of a gap is needed at the top and bottom when installing the radiant barrrier?"

For more information on gaps and airflow see: How much of a gap should I leave at the tops and the bottoms of the foil to allow for proper ventilation?

Run the 48" wide foil horizontally (from left to right) across the rafters, starting at the bottom and working your way up. This is usually the best method for wide open spaced attics. For attics with truss systems, try the 26" wide radiant barrier that is specifically made for easy vertical installation. You want to cover as much as you can as fast as you can, which is why the horizontal application is suggested.  You do not have to run the foil horizontally, it will work parallel too; the direction has no effect on the performance.

Using either a measuring tape or just counting, count the rafters in your attic space along one slope of the roof; rafters are usually 24" or 2 feet apart. Count them and add about a foot to your final number to make sure you don't run short.

Cut pieces outside the attic. The best way is to cut several pieces at a time and work in sections. The driveway works well. Use a standard utility knife and have some extra blades handy. Don't use scissors, they will quickly get dull. Use a cardboard box as a cutting board. If you plan ahead, you can cut 5-10 pieces at a time and minimize trips into the attic. This is a perfect job for a helper to do.

Tip: Take the ends of your cut pieces of the AtticFoil® and pull them together, then fold or roll up the foil. When you are in the attic, you and your helper can each grab an end and pull it out full length. This method will keep the foil from getting folded up or wrinkled.

Start at the bottom and work your way up.

Most installs go best when you start at the bottom with larger pieces and work your way up toward the top of the space. This enables the first piece to be pulled across and level.

Use a helper and pull the first piece across the space, leaving a small gap (3-6") at the bottom. You can start the foil all the way at the bottom of the rafters, but if you do this, make sure you have open soffit vents in the section to provide intake attic ventilation. If you have no soffit vents (or a lack of soffit vents in this area), you need to leave a gap at the bottom.

Continue moving up with your next piece of foil. It does not have to be pretty; if you get the foil between the roof and the attic insulation, the foil will work correctly. Seams can be overlapped, butted against each other or leave a small gap between pieces. Remember, you are using perforated foil; therefore, the installation will not be airtight.

Either cut around bracing and other obstacles, or just go over them. The foil does not have to be perfectly smooth. You can use a foil air-conditioning tape to patch foil back together after cutting, but you do not have to do this. When cutting around objects, don't worry if it is not a tight fit - a few gaps are OK.

Tip: Use a pen/marker to mark a common distance on the rafters (about 52" up from the floor joists) to help guide your first run of foil.  This helps the foil stay level, prevents uneven stapling that could result in crooked runs or useless overage on one end of the attic and it ensures about a 4" gap at the bottom of the install for air flow.

For more tips on installing around obstacles or in attics with a bunch of twists and turns, see the section below on alignment and blocking.

 The final installment of the 3 part video series on installing AtticFoil radiant barrier foil covers installation around obstacles (braces, supports, vents, etc.) in the attic and the basics of attic ventilation and how it contributes to reducing the heat load on the home.

Keep in mind that good attic ventilation is important because keeping air moving through an attic not only keeps the air temperature cooler in the attic, but it also helps to remove moisture.  

Just like we mentioned in the section above, you want to install the foil so there is a gap at the bottom and a gap at the top of the attic. Regardless of the type of ventilation systems you have, this is the best way to do it.  When done this way, fresh outside air will enter the attic low at the soffit level and it will go one of two routes: either up the channel created by the foil (between the roof deck and the foil) or it will come into the attic below the foil.

As hot air accumulates, it will move toward the top of the attic, just like water in a bathtub migrates toward the open drain.

The hot air will find its way out your exhaust vents (whether that is a ridge vent, gable vents, powered fans, etc.) and allowing the air to easily flow throughout the attic promotes a cooler attic air temperature as well as maximum potential for reducing moisture.

The main thing is to allow the air to flow as freely as possible, while still maintaining a good coverage.  There is not an exact science as to how large the gaps need to be, just make enough so the air has a path to escape out and leave the attic. The simple way to look at this is: air should flow though the attic as though the foil is not even there.

Alignment & blocking

Sometimes the foil and the attic framing supports don't line up perfectly. You can either cut a strip and staple below the support. Or, you could go OVER the TOP of the support and encapsulate it in foil and connect to the bottom piece of foil.

You might have what is called "blocking" between your rafters. These are cross-supports to add strength to your roof. The blocking will also constrict airflow behind the foil. You have two options: 1) let the foil "droop" an inch or two below the area with blocking to allow air to bypass or go around the blocking. 2) Cut around the blocking to allow air to exit/enter. Either way works. All you need is to do is create a path to keep the air moving to the top of the attic.

Continue to work your way up to the ridge. STOP the foil about 3-6" from the ridge. This gap will allow a pathway for air to "pool" in the top of the attic. The hot air will then exit the attic through either your ridge vents, wind turbines, electric or solar fans or static vents. Homeowners really tend to get too concerned about this. It's OK if your "holes" in the attic are not at the highest part of the roof at the ridge. Just think of the air like water and it is "draining" out the top.

Cut holes in the radiant barrier below ALL exhaust vents about 6" larger then the actual vent holes. It is important to create a pathway for cool air to come in the bottom of the attic and heated air to go out the top of the attic. With normal ventilation foil will ONLY increase shingle temperatures 2º-10º which is acceptable and will not damage or shorten the life of your roof.  For more information on adding a radiant barrier to your home and how if effects the life of your roof and shingles, read our article on Myths: Radiant Barrier and Roof Temperatures.

Roof Hips & Valleys 

Roof Hips and Valleys should be treated like any other part of the roof. Remember, you want to create a path for air to flow behind the foil and then up and out. On hips and valleys this is done by simply cutting a hole or slit at the top and the bottom of each cavity. Air will naturally be drawn in the bottom and out the top. Ultimately all hot air will end up in the top of the attic and be exhausted by whatever exhaust vents you have.

You want air (attic ventilation) to continue to flow through the attic as though the radiant barrier foil is not even there. A slot is left along the ridge, on any hips or valleys, and around roof vents to allow air to flow from the soffits to the top of the attic and then vent out the top of the attic. The holes (demonstrated in the photo to the right) are small, about the size of an adult hand.

Radiant barrier should be installed so that it does NOT interfere with attic ventilation.  Have you watched our video about the proper gaps for airflow when installing a radiant barrier?

Gables are the "flat" ends of the attic – Run the foil across the framing. Leave a small space at top and bottom of gable ends. You want air to be able to flow behind the foil. Install radiant barrier on gable ends that get direct sun - East, West and South facing. Do any North facing gable sides last or if you have extra foil. 

You want outside air to still enter the bottom of the attic and vent out the top exhaust vents. Remember - Hot air will rise to the highest point - just give it a path to get there. Don't worry, all hot air ends up in the top of the attic. It does not matter if you have ridge vents, wind turbines, gable vents, fans or other vents the hot air will find the top of the attic. You DO NOT have to have ridge vents for radiant barrier to work. It's OK if your top exhaust "hole" is off the ridge (wind turbine or other type vent).

More info: Installing Radiant Barrier on Gable Walls 

If you want to add insulation to your attic floor at a later time, you can use one of two methods to do this: the skirt method or the slit method.

The Skirt method create a skirt, or overhang of foil. This method should ONLY be used if you have adequate soffit vents in the area where the skirt method is used. The skirt method is good if you plan on adding additional insulation later. It will act as "back stop" to keep the insulation from blowing into the soffits. The RED line shows how the foil is folded back.

The Slit method is when the first piece of foil goes as far down as possible. This first piece will keep insulation from falling down into the soffit. Then, leave a small slit/space/gap 1-2" between the lowest piece of AtticFoil® and the second piece. Ideally, you want air to enter behind the foil from the soffits. This "slit" method will allow attic air to enter behind the radiant barrier foil and help with good attic ventilation. 

Notice the open slot at the ridge for ventilation. Use this method in lower attics and dormers even if there are no exhaust vents. The air will move out and then make its way to the upper attic sections.

To make install easier, you can cut or pull down the ducts straps. Then, once the installation is complete, nail the straps back into the rafters through the foil. Or, if codes will allow it, leave the ducts on the ground, but be sure to keep them straight and try to eliminate sharp turns. Then, bury the ducts with blown-in insulation.

Buy radiant barrier foil.

The ceiling in most this the house is 9'. So getting all the way down into the 3-4' slanted area between the roof decking and the ceiling sheetrock was impossible. The customer decided to just block that area off.  

He did long runs above and below the supports, then came back later and patched the holes between each truss.  Also, notice how the vents holes are not covered with foil, but open for exhaust.

This customer doesn't have a ridge vent, just 5 of the circular vents. Therefore, he stopped the foil just before the vents to leave a clear path for the air to escape. 

For the runs on the lower right, he folded the foil across its length, then rolled it up. This made it much easier when hanging it in place. 

When necessary, cut holes or slits in the foil so air can escape and vent out through the exhaust vents.  Here the customer cut slits in the foil installation to push the blocks through.

Cutting around supports is part of most installations. It goes fastest when you do the wide open runs first, then go back to these.