FAQs About Radiant Barrier Foil Insulation

General Questions

What is a radiant barrier?

A radiant barrier is made of highly reflective aluminum and is typically reinforced with a middle fabric layer making it puncture and tear resistant unlike basic kitchen foil.

Unlike mass insulation that merely slows down or resists the transfer of heat, a radiant barrier BLOCKs the transfer of a large percentage of radiant heat (at a minimum 90% as prescribed by the official Department of Energy definition of a true radiant barrier).

Radiant barriers BLOCK radiant heat by reflecting it back towards the direction it came as well as REDUCE convective heat by acting as a blockage against convective air flow. 

With a radiant barrier properly installed, you can significantly reduce the amount of heat that common insulation materials merely slow down thereby maximizing the efficiency of your existing insulation materials making your living space more comfortable while reducing your overall energy utility costs.

What is radiant heat?

An example of radiant heat is the heat you feel on your skin when you walk out from under a shelter into the direct sunlight.

Exactly how does radiant barrier foil insulation work?

Simply put, a radiant barrier reduces the transfer of a large percentage of radiant heat in one of two ways: 

1. a radiant barrier REFLECTs a large percentage of radiant heat that strikes it surface across an air space back in the direction from which it came, and

2. it EMITs a very small percentage of radiant heat from its own surface facing an air space.

Noticeably above, the words "air space" are used in describing both methods a radiant barrier utilizes to reduce the transfer of radiant heat.  For a radiant barrier to be effective in any installation, and air space of at least 3/4" of an inch must exist on at least one side of the radiant barrier.

Why is my attic space hot and how will a radiant barrier keep it cooler?

All materials have some degree of reflectivity and re-transmission of heat.  The shingles, tar, and plywood comprising a typical roof absorb radiant heat from the sun and conduct this heat through to the plywood decking.  Because plywood decking emits approximately 82% of its heat, your attic gets hot.

A RadiantGUARD® radiant barrier stapled to the underside of the decking or rafters would emit only 3% of the heat from the plywood decking resulting in an overall cooler attic which means less heat to enter your living spaces resulting in lower utility bills.

How much money can I expect to save on my utility bills if I install a radiant barrier in my attic?

Although RadiantGUARD® radiant barriers BLOCK 97% of radiant heat, your utility bills savings will vary because some homes are more energy efficient than others and because of other forms of heat flow in a building structure that contribute to the total cooling (or heating) load.  Data varies by region.

Based on a radiant barrier study performed by the Tennessee Value Authority, savings averaged approximately 9% with some results found as high at 17%. 

Is a radiant barrier the same as basic kitchen foil?

Basic kitchen foil is not the same as a RadiantGUARD® radiant barrier.  Basic kitchen foil is much thinner than a typical radiant barrier product and lacks the middle scrim layer that adds durability in the form of puncture and tear resistance that exists in RadiantGUARD® radiant barriers.  Our radiant barriers are almost impossible to tear by hand unlike typical kitchen foils.

More importantly, the shiniest of kitchen foils only reflects an average of 88% of the radiant heat whereas RadiantGUARD® radiant barriers reflect a much higher percentage at 97%.

Also, our radiant barrier foil insulation products are available in a perforated version to allow moisture to pass through reducing condensation issues.  Kitchen foil is not perforated and therefore, traps moisture.

What's the difference between a radiant barrier and the "so-called radiant barrier paints?"

There's a big difference!  A true radiant barrier reflects 90% or more of the radiant heat.  The most effective reflective paint reflects only 78% of the radiant heat. 

Such reflective paints are NOT radiant barriers as they don't meet the minimum 90% reflectivity requirement set forth for radiant barriers by the Department of Energy (DOE).

How does a radiant barrier help me in both the winter and summer months?

During the warmer months of the year, a radiant barrier in your attic will REFLECT the radiant heat from the sun that attempts to enter your living spaces from your attic.  This can reduce heat transfer from the attic to living spaces by 16-42% which can result in increasing the comfort level of your home or building, reducing the usage of the air conditioning unit, and thereby, reducing utility bills up to 17%.

During the cooler months of the year, a radiant barrier works similar to wrapping hot foods in aluminum foil to keep them warmer longer.  Baked potatoes and pizza are both great examples of hot food products that are kept warmer by being wrapped in aluminum foil.  With a radiant barrier in your attic, the heat generated within your home is REFLECTed back down to your living space inside the home and results in increasing the comfort level of your home or building, reducing the usage of the central heat or furnace, and thereby, reducing utility bills up to 17%.

Will a radiant barrier in my attic cause my roof shingles to get hotter, degrade, or void the  shingle warranty?

A radiant barrier may cause an increase in shingle temperature between 2-5 degrees Fahrenheit on a hot summer day.  Given that shingle temperatures on a hat day is in the range of 160-190 degrees, this increase is negligible and does not accelerate shingle degradation.

Radiant barrier foil insulation has been used extensively in the south, showing negligible differences in roof temperatures, as confirmed by field tests.  Read more about radiant barriers and roof shingle temperatures.

What is the "R" value of a radiant barrier?

Radiant barriers do not "absorb" heat like mass insulation (fiberglass, cellulose, foam, etc).  Instead, our RadiantGUARD® radiant barriers, with their highly reflective surfaces, reflect 97% of the radiant heat that hit their surfaces and therefore, have no R-value rating.

Installing a radiant barrier between the heat source (sun) and an existing R-Value rated insulation will improve the effectiveness of the R-Value rated insulation.  Why?  Because only 3% of the radiant heat is now hitting the R-Value rated mass insulation thereby extending the amount of time it has to absorb heat before becoming saturated and passing the heat into your living spaces.

Do I have to have other insulation in my attic for a radiant barrier to be effective?

No; a radiant barrier works independently of other insulation products. 

If you currently have no insulation in your attic space, you will most likely see a greater reduction in your utility bill by adding a radiant barrier than someone adding a radiant barrier to an attic full of existing insulation.

This does not mean that you don't need other insulation products in your attic.  Mass insulation, like fiberglass insulation, blown-in cellulose, and rock wool, work to protect you against conductive and convective heat flow and therefore, when used in conjunction with a radiant barrier, give you the best overall protection for reducing the transfer of radiant heat.

I already have plenty of insulation in my attic.  Do I really need a radiant barrier?

Regardless of how much insulation you have in your attic, adding radiant barrier foil insulation will save on your heating and cooling expense, and keep you much more comfortable.  Energy savings for heating and cooling can be as much as 17%, depending on a number of factors, including climate, building configuration, materials used, site, family size and lifestyle.

Quotes from notable studies on radiant barrier:

• "A radiant barrier system can stop 97% of the thermal radiation across an attic space.  If it is not stopped, that radiant energy would be absorbed by the ceiling insulation and eventually be transferred to the living space below."  "The Solar Collector," Quarterly Newsletter of the Florida Solar Energy Center.

• "The heat storage capacity of reflective insulation is low.  As a result, it does not store heat during summer days, only to pass it on down into the rooms of the house from the attic at night when coolness is most apt to be desired from the point of view of sleeping comfort."  "Progressive Architecture," Nov. 1949, Page 76.

• "Reflective foil retrofitted to fiberglass insulated . . . buildings is demonstrably effective in reducing heat loss . . . Installation of foil in uninsulated buildings would show even more pronounced reduction in heat loss."  "Effects of Reflective Foil On Heat Loss in Attic Floors and Metal Building Installations," Northeastern Illinois University, Prof. Charles Shabica, May 20, 1986.

Are radiant barriers tested by qualified independent testing agencies or governmental agencies?

The Florida Solar Energy Center at Cape Canaveral has tested radiant barriers in both small scale laboratory and full scale building models.  Their results indicate that radiation barriers provide significant resistance to heat transfer. 

Current tests conducted by the Tennessee Valley Authority and the University of Mississippi support the findings at the Florida Solar Energy Center. 

Northeastern Illinois University conducted winter tests in residential and commercial structures using infra-red thermograph photography.  The photos showed significant resistance to heat transfer over the regular insulation.

Reliable individual brands of radiant barrier products are tested by the American Society for Testing and Materials (ASTM) and result in verified and uniform product specifications that can be trusted when researching a radiant barrier to purchase.

All RadiantGUARD® radiant barrier products meet the Standard Specifications for Sheet Radiant Barriers for Building Construction Applications ASTM C1313 and the State of California Title 24 Insulation Standards.

Installation Questions

How should I install a radiant barrier in my attic?

Please see our Where & How to Install page for the most common radiant barrier installation methods.  Our instructions can be easily reviewed online, printed, and even saved to your local PC for later reading.

Do I need a a radiant barrier or bubble insulation for my my attic?

There is no need to purchase and install the more expensive reflective bubble insulation for your attic space as it will end up performing exactly the same as a radiant barrier which is almost 1/2 the cost.  However, you certainly can install the reflective bubble insulation in your attic space but stapled to the roof decking or underside of rafters ONLY.  You cannot lay a bubble insulation product over the attic floor because it is a vapor barrier (not perforated like our radiant barriers) and will trap moisture that rises from your living space thereby causing condensation and potentially causing water damage in your attic space.  If you want to install one of our products on your attic floor, you must choose one of our perforated radiant barriers: Standard, Premium or Ultima.

Do I need a perforated or solid radiant barrier in my attic?

A radiant barrier used in the attic floor application MUST be perforated to allow water vapor from your living space to to pass up through it and be carried out your attic via your attic ventilation. This is necessary because, during the winter, if there is no effective vapor retarder at the ceiling, water vapor from the living space may condense (and even freeze) on the underside of a solid radiant barrier lying on the attic floor and cause water damage to the ceiling and any existing attic floor insulation. Why? Because warm moisture laden air always moves towards cooler air and will condense on surfaces trapping the air if it is not a perforated material allowing the moisture laden air to pass through it and out the building structure.

Read more here to determine if you need a solid radiant barrier.

Can I install a radiant barrier directly underneath my shingles when re-roofing?

No, a radiant barrier needs at least a 3/4" air space on at least one side of it for it to be effective.  If a radiant barrier were sandwiched between two solid surfaces, it would merely conduct heat all the way through it as if it were not installed.  The best location for installing a radiant barrier is in your attic space.

If I install the radiant barrier partially under the rafters and partially over the attic floor, will I see benefits?

Yes, you will receive some benefits, HOWEVER, you won't receive the maximum benefit provided when you fully install to either the rafters or attic floor.  Why?  Simply because you're leaving open spaces for heat to penetrate through the roof and then through the ceiling to the living spaces below. 

When you install to the attic rafters in all parts of your attic, you block the radiant heat from heating up your attic space thereby eliminating it from entering your living spaces.  If you install to the attic floor in all parts of your attic, you block the heat within your attic from entering your living spaces.

Some people gain even higher savings by fully installing on both the attic rafters and the attic floor.  The radiant barrier on the attic rafters blocks 97% of the radiant heat from the roof decking and then the radiant barrier on the attic floor blocks 97% of the radiant heat that made it through the attic rafters location. 

This very issue has been studied by several research institutes.

An exhaustive test performed by James R. Hall, project engineer for the Tennessee Valley Authority concluded that "... dust appeared to have little effect on the effectiveness of the radiant barrier.  The percent reduction in ceiling heat flux was remarkably similar to that of a radiant barrier with no dust.  He stated that a radiant barrier's performance "...may not degrade nearly as much as would be expected from the significant increases in emissivity caused by small amounts of dust." Click here to read the report - summary conclusion is on page six.

What size staples work best with the radiant barrier and bubble insulation?

We recommend using 5/16".

Do I need to tape the overlapping seams when I install the radiant barrier in my attic?

Taping of seams is generally only done when using a solid radiant barrier or bubble insulation and you're trying to create a vapor barrier.  We recommend using a perforated radiant barrier in the attic and therefore, there is no need to tape any seams.  However, a solid radiant barrier or bubble insulation can be used on the attic rafters if desired and you can tape the seams for aesthetics or to create a vapor barrier.

Product Questions

What is the difference between RadiantGUARD® Standard,  Premium and Ultima radiant barrier??

The primary differences in RadiantGUARD® radiant barriers are in the weights and the puncture and tear resistance characteristics. 

Ultima is our most durable and industrialized radiant barrier with an extremely high puncture and tear resistance factor.  It is ideal stapled to the underside of roof rafters and stapled to wall studs as a house wrap.  Ultima perforated can also be laid over the attic floor.

Premium is our next durable version and is the most versatile of our radiant barriers ideal for both stapling to attic rafters and laying over the attic floor. It weighs almost 1/2 the weight of Ultima making Premium very easy to handle.  While it's not as puncture and tear resistant as Ultima, which is almost impossible to tear by hand, Premium is reinforced with a durability scrim layer giving it resistance to tearing.

All RadiantGUARD® radiant barrier products are high quality, double-sided, tear and puncture resistant radiant barrier products of higher quality than many of the other radiant barrier products in the marketplace.  Each radiant barrier version BLOCKs 97% of the radiant heat.

Ultima is recommended for the rafters but I want to use it on the attic floor.  Is that okay?

Yes, the Ultima perforated version can be used on the attic floor and is ideal if you plan to cover plywood decking and walk on it.  Otherwise, our Premium perforated is very suitable for the attic floor when extreme durability isn't required.

Are both sides of the radiant barrier the same or is there a top side and bottom side?

All our radiant barriers are double-sided and exactly the same therefore, it doesn't matter which side faces which direction.

My rafters are 24" apart.  Do you carry a 24" wide product?

All our radiant barrier are 48" wide and most commonly installed across the rafters spaces therefore, it doesn't matter how far apart the rafters are.  If for some reason you want a 24" section for installs, you can quite easily cut an entire roll of radiant barrier in half with a hacksaw resulting in two 24" mini-rolls.

Questions About Orders

How do I cancel an order?

Please call customer support toll free at (866) 528-8412 option 1.  We will assist you in cancelling your order and issuing you a payment refund.

I received a shipping tracking number but FedEx.com doesn't show a current status of my package(s).

FedEx.com will show a current shipping status once they actually pick up your order from our warehouse and scan it into their system.  If you currently do not see a shipping status on the FedEx.com website, wait until the end of the next business day after your order was placed.  You should be able to inquire on the shipping status at that time on the FedEx.com website.

Can I return any unopened rolls of RadiantGUARD® for a refund?

Yes, please see our Return Policy for information about the conditions under which we will accept a return for a refund.