A radiant barrier runs along the ceiling of an attic in a home

A radiant barrier is a particular building material designed to reflect thermal radiation. This technology has existed for many decades and has become an essential component in energy-efficient homes. 

Most homeowners can benefit from installing the proper barrier in their homes. However, you may have specific questions regarding this technology.

This guide will answer some of the most frequently asked questions related to radiant barriers.

How Do Radiant Barriers Work?

The term “radiant barrier” does an excellent job of explaining what this technology is and what it does.

The ‘barrier’ portion of the name describes how it acts as a barrier that keeps heat inside your home and prevents external heat from coming inside. The ‘radiant’ portion of the name describes how the barrier blocks heat transmitted via radiation, including heat from the air outside on a hot day.

It also includes the heat generated and spread around your home through a heating unit.

How Long Have Radiant Barriers Been Around?

Radiant barriers were initially developed in the 1920s. Infra Insulation was the first brand to introduce this technology to the masses.

The company produced and sold a product called INFRA Insulation, designed to keep the external heat from entering homes in summer and internal heat from escaping in the winter. However, this product was taken off the market in 1965 after an unfavorable FTC ruling.

Other companies began producing their own types of barriers in the late 1960s, including products made from aluminum Kraft paper, aluminum-faced cardboard, and aluminum-faced fiberglass.

What Types of Radiant Barriers are Currently Available?

These days, three types of radiant barriers available.

Foil

Most barriers use foil such as aluminum for its metallic properties. It is light and uses its shininess to reflect thermal radiation. It also possesses low emissivity, meaning that it produces only a low amount of infrared energy.

Plywood

Also called radiant barrier sheathing, this form of heat shield typically consists of aluminum layers bonded to engineered wood or plywood panels.

Closeup on the corner of two radiant barrier sheathing boards
Courtesy of Georgia-Pacific

Silver

Silver is the main reflective component in radiant barrier ‘chips.’ This technology is often used in roofs and attics with unorthodox designs due to its small dimensions. Such chips can be placed in hard-to-reach spots to minimize the heat gain.

Are Radiant Barriers an Alternative to Insulation?

Radiant barriers are not an alternative to insulation. Their job is to block heat from entering or escaping your home via radiation. Insulation also serves as a sort of heat barrier. However, its job is to prevent heat from entering or escaping your home through conduction.

Insulation does an excellent job of slowing down the heat as it penetrates your home’s walls, so it’s possible to have a reasonably energy-efficient home with the proper insulation. Homeowners can reduce their energy consumption by installing insulation and a barrier. This combination will reduce heat loss or heat gain through both conduction and radiation.

Does a Radiant Barrier Keep the Cold Out?

It’s incorrect to say that a radiant barrier “keeps the cold out.” However, it does serve as a solid barrier that prevents cold air outside from entering your home. More importantly, it prevents the heat in your home from escaping via radiation.

It is estimated that up to 10% of heat loss in homes occurs via radiation.

Homes without radiant barriers would lose heat more quickly during winter, leading to colder internal temperatures.

Do Radiant Barriers Reduce Attic Temperatures?

Attics tend to be warmer than other parts of your home because they are located under the roof, which is directly in contact with sunlight. This means the roof heats up and transfers heat to the attic below.

Adding a barrier reduces heat transfer from radiation and keeps your attic cool. It is difficult to predict precisely how much more relaxed your attic will be after installing one. However, many manufacturers state that their barriers can reduce attic temperatures by 20-35 degrees. This significant temperature difference can lead to long-term savings on your air conditioning bills.

A radiant barrier paint application in an attic

Why Do Radiant Barriers Need an Air Gap?

Radiant barriers must have a small air gap between the material and the home’s wall to function at their best. If the barrier was placed directly against the home’s wall, heat from the wall would pass through via conduction.

This transmission happens because the radiant barrier is designed to block heat from radiation and not conduction. Therefore, placing a barrier against the wall with no gap will lead to external heat entering the home and internal heat escaping quickly, which nullifies the energy savings they create.

Most manufacturers recommend leaving an air gap that is ½” to ¾” in width. This size gap also helps promote ventilation and keeps the air around the barrier dry.

Do Radiant Barriers Affect WiFi and Cellular Reception?

WiFi and cellular reception are transmitted through electromagnetic waves, as is heat radiation. A radiant barrier is designed to block heat radiation. Therefore, it may impact WiFi signals and cellular reception in your home. However, this effect is limited.

Foil barriers are 3/1000″ to 5/1000″ thick, enough to block a significant percentage of radiant heat but not wide enough to block radio waves.

In addition, they typically cover only 20-30% of your home, meaning the remaining walls will allow radio waves to pass through.

Do Radiant Barriers Have R-Values?

All forms of insulation possess an “R-value” that describes their ability to reduce heat movement through their surface. A high R-value means the insulation does a great job blocking heat transfer.

Radiant barriers do not have R-values associated with their effectiveness because they do not absorb heat like insulation does. Instead, they reflect heat rather than absorb it and slow it down, meaning an R-value would not be able to describe what it does.

Do Radiant Barriers Prevent Condensation?

Some types of radiant barriers are prone to developing condensation. Condensation usually occurs due to the significant temperature differences between the environment above and below the barrier.

If left unchecked, this condensation can lead to mold developing over time. Mold can become a severe problem, so homeowners must monitor for any condensation during winter.

Plenty of barriers are designed to combat condensation issues, including permeable or perforated. Homeowners can also opt to seal cracks and air leaks in their home’s ceiling to avoid creating high humidity conditions indoors.

Are Spray-On Radiant Barriers Effective?

Spray-on radiant barriers are a recent development touted to perform the same functions as traditional radiant barriers. They are a spray-on low emissivity compound applied to the underside of your home’s roof deck.

Most spray-on barriers resemble paint and are easy to apply to surfaces. Spray-on barrier manufacturers tout their products as being able to reflect 56% of heat from outside away from your home.

Is Spray Foam Insulation an Alternative to a Radiant Barrier?

Spray foam insulation is not supposed to be an alternative to a radiant barrier.

This insulation’s application process is different from that of other insulation types. However, it still serves the purpose of slowing down heat transfer through conduction and convection.

A picture of spray foam insulation covering the floor and wood studs in a wall.

Homeowners with spray foam insulation will still need to invest in a barrier if they wish to keep heat from radiating out of their homes during summer and retained indoors during winter.

How Much Do Radiant Barriers Cost?

Radiant barriers vary in cost from $0.10-$0.95 per square foot of material. Installation costs also vary from $700-$2,000, depending on the home’s size and the installer’s charges.

Such costs may seem high to homeowners. However, these costs will be offset by a fardel of energy savings in the long run.

It is estimated that radiant barriers can help you save between 5-10% on your air conditioning bill if you reside in a warm climate, meaning they make up for their purchase and installation costs within just a few years.

Can Barriers Be Installed On Only Select Roof Areas?

Some homeowners may install a barrier on only specific roof parts, leading to some energy savings over time.

However, this arrangement will also reduce the barrier’s effectiveness if it can’t envelop the entire surface. For this reason, homeowners should consider adding a barrier to their entire roof.

Are Radiant Barriers a Fire Hazard?

Most radiant barriers are not considered fire hazards. Their principal component is aluminum which melts when it is exposed to high heat. However, certain barriers, such as the variety containing cardboard, may catch fire.

Homeowners concerned about the fire hazard nature of a barrier should opt for the plastic varieties as they have a low flame rating.

Do Radiant Barriers Attract Lightning?

Radiant barriers may attract lightning because they contain metal. However, experts are unsure how prominent this risk is.

For example, it is believed that a rooftop containing a barrier is more likely to be struck by lightning than a rooftop that does not include one. This is one of the downsides associated with them that homeowners should be aware of.

Can a Barrier Be Installed In an Existing Structure?

Homeowners must install most forms of insulation during their home’s initial construction.

However, this same rule does not necessarily apply to radiant barriers. While most barriers are generally installed in new homes, they can be added to spaces in existing homes.

For example, it is relatively easy to add a one to an open attic with the help of a trained professional.

Will Installing a Radiant Barrier Damage My Roof’s Shingles?

Some homeowners may believe that installing a radiant barrier could harm their roof in the long run because they reflect the heat they receive from outside upwards and back onto the bottom of the shingles covering the roof.

Studies have found that these barriers do increase the amount of heat transmitted back to shingles. However, this amount raises the shingles’ temperature by only a few degrees, meaning they may damage your shingles over time, but by only a minor amount.

How Long Do Radiant Barriers Last?

Radiant barriers can last between 80-100 years if installed correctly. This timeframe means your barrier is likely to last a lifetime. Therefore, homeowners should invest in a good quality product if they want to create near-permanent energy savings in their homes.

Final Thoughts

Homeowners can use the above guide to learn more about radiant barriers and the considerations associated with choosing and installing them.

The right choice can help make your home more comfortable and save you thousands of dollars on your energy bill in the long run, so be sure to choose a high-quality product and hire an experienced professional to install it.

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