Although radiant barriers have gained popularity in the insulation market for their energy efficiency in keeping a comfortable conditioned space at home, they’re also known for their undeniable problems.
Problems and concerns about installing radiant barriers typically arise due to faulty installation, environmental factors, and even deceptive or aggressive marketing in sales. If your radiant barrier is improperly installed, then its effectiveness will decline.
So what are the disadvantages and concerns one can face when installing a radiant barrier? If you’re planning to install a radiant barrier in the attic, you must know the pros and cons to make an informed decision.
Below, we’ll take an in-depth look at some problems and concerns that arise with radiant barriers, along with precautions and solutions to avoid them.
What Is Radiant Barrier And Why Do They Get a Bad Rep?
A radiant barrier is a reflective building material that reduces and prevents the transfer of about 90 to 97% of the radiant heat (energy from the sun or other sources). Radiant barriers are often confused with reflective insulation as they work similarly and reflect the radiant heat away from the attic’s surface, roof’s underside, and other directions to keep the heat from entering the home.
A radiant barrier acts as an additional layer and a boundary against radiant heat between the sun and conditioned air space. It is typically combined with other insulation materials to serve as additional thermal insulation facing material, reducing building heating and cooling energy usage.
Radiant barriers are typically made of a highly reflective material, usually, a sheet or coating of aluminum foil applied on at least one or both sides of the substrate materials. Common substrates include kraft paper, cardboard, plastic films, air infiltration barrier material, and oriented strand board. In addition, some radiant barriers are reinforced with fiber to increase durability and make them easier to handle.
According to the Department of Energy (DOE). in order to be classified as a radiant barrier, the product must have a high reflectance rate of 90% or more or a low emittance rate of 10%.
Before we analyze the undeniable disadvantages of radiant barriers, let’s first look at its benefits, including:
- Attic temperature drop. show Radian barrier can facilitate a noticeable attic temperature drop as low as 30 degrees Fahrenheit. It was also shown in various tests of Oak Ridge National Laboratory (ORNL) that a radiant barrier reduces 16% to 42% of ceiling heat gains in attics with R-19 insulation compared to an attic with the same level of insulation but with no radiant barrier installed.
- Relatively low cost of installation. The total radiant barrier installation costs around $700 to $3000 or $1,700 on average, including the materials and labor costs if done by a professional. The cost of a radiant barrier for the material alone usually ranges from $0.10 to $0.25 per sq. ft (single-sided) and $0.15 to $0.50 per sq. ft (double-sided). For the installation fees, professionals commonly charge the labor about $30 to $80.
- Lower cooling bill. Since a radiant barrier helps reduce the ceiling heat gain and transfer, it’s an effective way of lowering the cooling costs by about a minimum of 5% to 10% with a maximum of 17%, especially when it’s used in hot climates according to the US Department of Energy. It also helps reduce the cooling bills from your HVAC system.
- Non-toxic. Unlike other insulation types, radiant barriers are safe to use at home because they are made of non-toxic materials, usually sheet or coating or aluminum foil. It’s also non-carcinogenic and doesn’t irritate the skin, eyes, and lungs.
Here are the disadvantages of using a radiant barrier.
1. Doesn’t Work In Every State or Climate
Radiant barriers are more effective in locations with warm to hot climates than in cold or freezing temperatures. Although it still works in colder climates, it was found that using radiant barriers may block or counteract the solar heat gain in winter. This means the HVAC system would need to work harder, increasing energy consumption to keep the conditioned space warmer with stable temperatures because of the loss of solar gain.
Moreover, radiant barriers are not applicable in every state because each state has different climate zones with various local building code requirements determined by the U.S. Department of Energy. This means you have to adhere to the requirements for each building envelope area for your region.
2. Efficiency Depends On Proper Installation
In order for radiant barriers to function effectively, they must be installed properly. Although you can install radiant barriers yourself, it’s best to let a professional installer do it instead because the installation process is quite complex, and specific manufacturer instructions need to be followed.
Local building codes and safety precautions must also be met.
A radiant barrier can be attached near the roof, to the bottom of the rafter framing or attic truss chords, directly to the roof deck’s underside, or over the rafter’s tops before the roof deck is applied.
If the radiant barrier is one-sided, the reflective surface must face the open air space to reduce heating and cooling loads effectively.
Another important factor to consider is how you insulate the area because it can interfere with how the radiant barriers work. Radiant barriers must face the radiant heat source to work correctly. Maintaining an air gap ( about a quarter of an inch to 10”) between the insulation and an installed radiant barrier is also essential because it will allow it to work properly and not become a means of conduction. If a radiant barrier is improperly installed, sandwiched between the heat source and the barrier, it will directly transfer the heat into the attic instead.
You cannot place the radiant barrier directly on top of the insulation in a ventilated area because it will accumulate dust on the foil surface facing the roof, negating the effect of the radiant barrier, and making it less reflective.
Additionally, improper installation of radiant barriers will cause moisture and mold build-up in the attic, resulting in a rotting roof, mold, and milder due to poor ventilation in the attic.
Although radiant barriers are sensitive to improper installation, some radiant barrier installation myths are going too far. Let’s debunk a couple of them.
One of the most well-known installation myths is that radiant barriers can cause the shingles to curl and the roof to overheat. However, this is not true.
According to a study by the Reflective Insulation Manufacturers Association International (RIMA-I), roofs with installed radiant barriers will slightly increase the temperature by only a few degrees, about 2 to 5 degrees Fahrenheit. But this small increase in temperature is still considered normal, and most roofing systems and shingles are designed to handle and even withstand temperatures above the maximum level.
A Florida Solar Energy Center test also has shown the presence of a radiant barrier when installed under a roof deck will only increase between 5° and 10°F. In addition, it was also found that the asphalt shingle colors have more effect on the shingle temperature than a radiant barrier.
Overall, this concludes that the radiant barrier, even with the slight temperature increase, will not cause overheating, curling, and damage to roofing shingles and the system itself. It will not also reduce the roofing shingle life or void the shingle manufacturer’s warranty.
Another common misconception about radiant barrier is that it degrades over time. Contrary to popular belief, radiant barriers may last up to 100 years, when properly installed. In addition, their quality and effectiveness don’t deteriorate over time, making it an energy-efficient and cost-effective insulation technique.
3. Dust Accumulation
As radiant barriers reflect heat, they must maintain optimal reflective properties. And one way for its reflective properties to decline is through dust accumulation. According to a Chicago radiant barrier study, a radiant barrier’s effectiveness can decline by ten times within two years solely because of dust.
Dust can accumulate when the radiant barrier is installed over or directly at the top of the attic floor’s insulation, allowing sunlight and heat to penetrate the roof and absorb instead of repelling it. When contaminants like dust or dirt accumulate in the radiant barrier, the reflective surface won’t be able to bounce the heat off.
It’s important to install the radiant barrier properly with adequate air gaps to ensure your radiant barrier is dust-free and provides optimal reflective properties. Air gaps promote proper ventilation on the foil surface. Another way to ensure proper ventilation is to ensure the air isn’t still and the vents are unclogged.
It is also possible to prevent dust accumulation by installing the radiant barrier in an open space with its reflective surface facing an open-air space, preventing dust accumulation.
4. Moisture Trap
Because of greater condensation probability, moisture can be a bigger problem for a radiant barrier in colder climates. This is especially a prevalent concern for locations with 32° F temperatures or less. However, condensation and moisture are not issues in hot or humid areas.
Moisture may build when the radiant barrier is directly installed on top of the insulation on the attic floors as water vapor may move and enter the attic from the interior of a house. This is also because the water vapor could condense on the radiant barrier’s underside. When this happens, this could result in mold and mildew build-up that could damage not only the radiant barrier but also the insulation.
In addition, condensation could reduce the effectiveness of insulation and radiant barrier as it becomes wet. It can also create water zones on your ceiling and could rot under severe conditions.
One precaution for moisture problems is using a naturally permeable or perforated radiant barrier. Additional precautions you can take include providing proper attic ventilation, sealing air leaks and cracks, and removing obstructions that could block existing vents.
5. Radiant Barriers Don’t Work On Its Own
Radiant barriers can effectively prevent radiant heat, but they won’t stop conduction or convection-driven heat gain. It is, therefore, necessary to insulate your house with thermal insulation, especially your attic.
A radiant barrier alone has an R-value of zero. Still, when used as supplemental to other thermal insulation, it will help increase the R-value of the insulation. So, you must combine radiant barriers with other insulation types to achieve an optimal energy-efficient conditioned space and comply with local building codes.
The bottom line is that the radiant barrier works together with thermal insulation, doing each other’s functions to make the house energy efficient and warm in the winter and cooler in the summer. A radiant barrier acts as the first defense against radiant heat, while thermal insulation is the second line of defense against heat gain.
6. Misleading Marketing
Installing radiant barriers has induced a lot of controversy and confusion because of the misinformation spread mainly through marketing and sale. For example, some companies promise impossible energy claims and projected savings calculations—the radiant barrier can cut the entire bill by 20% to 40%, which is untrue since what the radiant barrier does is help lower cooling bills.
Others have even provided claims with multiple references to NASA, telling how great an investment the radiant barrier alone is, with pitches over invitations to presentations. Other manufacturers and installers even overcharge for purchasing and installing radiant barriers in the attic.
The bottom line is to ensure you contact your local building authorities, regional planning department, or Division of Energy Resources (DER) for proper insulation and other energy-efficient measures in your area.