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Heating and cooling are the major components of any home energy bill. Radiant barriers reduce summer energy costs by blocking radiant heat transmission, but they don’t slow the loss or gain of conductive heat like conventional insulation products do.
In new construction, installers drape a rolled radiant barrier foil face down in the attic before roof sheathing goes on. They can also be installed in existing attics by stapling the material over the attic rafters. Read on Ultimate Radiant Barrier & Insulation for more details.
Radiant barriers are designed to reduce the amount of heat that is transferred from the attic space into the living spaces of a home by reflecting thermal radiation back toward its source. These barriers are typically installed over a typical attic floor or under the roof deck to provide an insulating layer that decreases energy consumption by reducing cooling costs.
There are three mechanisms of heat transfer: conduction, convection, and radiation. Radiation is the most common and causes things to feel hotter than they really are. When you stand in front of a window or woodstove, the radiant energy from the sun shining through it makes you feel hotter than the room itself. A reflective surface, such as the foil used in car windows, will reflect that radiant heat and prevent it from entering the interior of your home.
All materials give off, or emit, a certain amount of thermal energy by radiation at their temperature. All radiant barriers have a property called emissivity, which is a number between zero and one. The lower the emissivity, the better the radiant barrier. The emissivity of a radiant barrier is measured after it has been cleaned to remove any dirt, debris, or dust. This will ensure the emissivity is as low as possible for maximum performance.
The most effective location for a radiant barrier is on the underside of the attic insulation in a ventilated attic. Traditionally, these barriers have been installed on the attic floor, but this is a less than ideal installation as it can be difficult to keep clean and dust-free. It can also cause moisture to be trapped in the attic, which increases the dew point and can lead to fungal problems such as mold.
Many radiant barriers are sold as part of a package of other energy-saving measures, such as attic ventilation and spray foam insulation. These packages can cost more than they should, and you should be sure to compare prices and the R-value of each measure before choosing a package deal.
Adding a radiant barrier to your attic can improve the R-value of conventional attic insulation, and it may also help with air leakage between the attic space and the living areas of your home. However, radiant barriers do not work as a standalone solution. They must be combined with other energy-saving measures to make a significant impact on your utility bills.
While radiant barriers are extremely effective, they are not a substitute for attic insulation. Rather, they work in tandem with traditional mass insulation to block radiant heat. This results in a much cooler attic space and, therefore, a much cooler house. A cooler attic also allows conventional insulation to perform more effectively, further reducing energy costs.
A radiant barrier can be installed in homes with a variety of roof types, including shingle, tile, and iron. However, they are most commonly used in new construction and vented attics. They are typically stapled or draped beneath the rafters and trusses in an attic before sheathing is applied. This technique is known as a “raised floor attic.”
The foil on a radiant barrier has a high reflectivity rating (typically 90% or more) and a low emissivity rating (0.1 or less). This means it can reflect heat but doesn’t absorb it, which is why they are so efficient. All materials emit some radiation; the difference is that radiant barriers reflect the majority of radiated heat, so they significantly reduce the amount of thermal energy emitted from an attic or wall cavity.
In addition, radiant barriers are unaffected by humidity, unlike many mass insulations, meaning they will continue to operate at a consistent level regardless of weather conditions. This is especially important in Texas, where the summer temperatures can be quite extreme.
Many builders choose to use a pre-laminated radiant barrier sheathing, like oriented strand board, that is designed to be the building’s roof decking and radiant barrier in one. This greatly reduces labor and material costs during the construction process.
It is important to note that any radiant barrier product must meet certain fire ratings and test specifications to be considered a valid product. It is recommended to always look for a radiant barrier with current ASTM testing results to ensure that you’re getting the best product on the market.
Foil-faced plywood is a common form of radiant barrier sheathing. It consists of oriented strand board (OSB) with a layer of low-emissivity aluminum foil applied to one side. This type of sheathing is often used on walls but is also used in attics as a way to limit the amount of radiant heat entering a home. A layer of mass insulation is typically added to the attic over the radiant barrier to reduce heat transfer through convection and conduction as well.
It is best to hire a professional to install a radiant barrier, but if you decide to do it yourself, make sure you follow proper safety precautions. It is also recommended to stagger the work over several days so that you do not have to go up in the attic during extreme temperatures.
Radiant barriers help limit summer heat gain by reflecting radiant energy away from the roof. However, they do not reduce heat conduction like thermal insulation materials. This makes them an important addition to your attic, but not a replacement for it.
When installed properly, a radiant barrier can cut cooling costs by 5–10%. They can be used in new construction or incorporated into an existing attic in place of traditional insulation.
During the construction of a new house, an installer will drape a rolled radiant barrier over the OSB or plywood roof sheathing before it is put in place. This prevents dust from settling on the reflective surfaces of the material (double-faced radiant barriers are available). If you are installing a radiant barrier in an existing attic, it is usually easier to use a sheet of foil-faced plywood as the sheathing.
If you choose to use a sheet of foil as your radiant barrier, it can be nailed or stapled to the attic joists. When stapling, you should leave a small gap between the attic floor and the foil so that air can circulate through the attic. This air circulation will help maintain the temperature of your attic, which in turn will keep your whole house cooler. Alternatively, you can purchase radiant barrier sheathing that is pre-installed. A popular example is LP TechShield, which can be installed in an attic before the roofing shingles go up or from the inside of the attic after it is completed.
The reflective surface of a radiant barrier inhibits thermal radiation and can be used alone or in combination with other types of insulation. Radiant barriers have a higher R-value than traditional attic or wall insulation and can reduce cooling costs by up to 20%. Foil-faced paint can be applied to radiant barriers to help protect them from damage. However, before applying a coating of paint to a radiant barrier, it must be properly prepared. The foil surface of the insulation is nonporous and can be difficult to adhere paint to. Using an appropriate pre-treatment and a polyester paintbrush can help prevent the problem.
While it is possible to paint foil-faced insulation, the process is more complicated than painting other types of insulation. It is important to choose a paint that is designed for use on metal surfaces and can withstand high temperatures. Using ordinary latex or oil-based paint may cause the foil facing to peel. It is also necessary to use a galvanized metal etching primer before applying the finish coat of paint. Once the priming is complete, the foil facing can be painted with satin or semi-gloss paint.
When properly installed, radiant barriers can be an excellent way to reduce energy costs in Texas homes. They can effectively keep ductwork cool, which is especially important if the ducts are in unconditioned attics. In addition, radiant barriers can help reduce air pollution caused by the generation of electricity and increase the overall comfort of a home.
Radiant barriers are often combined with traditional insulation to provide the best results. This can be especially beneficial in attics where there is a lot of ductwork and/or where the ceiling is very low. A combination of a radiant barrier and attic insulation can help to improve the R-value of the attic space and provide increased insulating properties throughout the entire home.
Despite the many benefits of radiant barriers, they are not an effective solution in every situation. For example, they do not perform well if there are rafters or other obstructions in the attic, and they can be less effective in cold climates. In addition, some state and local governments have advised against their use because of misleading energy savings claims. For this reason, it is important to consult with your local planning and zoning department before installing a radiant barrier in your home or business.