A radiant barrier is a reflective insulation that can effectively block most of the heat entering or leaving your living space. Stopping radiant heat transfer is the surest means for reducing your heating and cooling needs. In summer, less radiant heat in your attic means that your air conditioning system will run more efficiently. In winter, when you want to keep the heat in, a radiant barrier can help your heating system run more efficiently by reflecting the heat inward.
Traditional insulating materials such as fiberglass, cellulose, and Styrofoam are able to absorb or slow down convective and conductive heat transfer. Radiant heat transfer is seldom discussed, but is a dominant form of heat transfer which traditional insulation does not block. The chart below explains the differences between these 3 types of heat transfer.
In your home, radiant heat is generated from charged particles converted into electromagnetic radiation. Radiant heat sources include sunlight streaming in a south or west facing window, a fireplace, or a radiator linked to a central boiler. It moves through the air without actually heating the air. The objects that are in the path of the charged particles, however, absorb the energy and heat up, radiating heat to other objects (like people) in the room. Everything in proximity to that space feels warmer.
Hot and Cold Facts
Radiant barriers are usually installed in the attics of homes. In warmer climates, radiant barriers are usually found under the roof rafters, reflecting back the heat generated when the sun meets the roof. Since the amount of heat meeting your home’s insulation has been largely blocked, the heat of the attic’s air temperature is greatly reduced. Anyone who has been in an attic on a hot, sunny day can appreciate this. Radiant barriers, then, protect ductwork and any items stored in an attic.
In cooler climates, radiant barriers work to prevent heat from the lower levels of the home from escaping. It is important to have a tight air seal in the attic at all times but, in combination with a radiant barrier, homeowners are going to significantly save on heating bills.
Benefits of Adding a Radiant Barrier
Adding a radiant barrier to work along with your current insulation can have great benefits. These include:
- Blocks up to 97% of radiant heat in the attic, saving up to 35% of home energy costs from the attic space’s impact on the energy use
- Reduces work load and extends life of HVAC system
- Lowers humidity in air conditioned areas
- Increases comfort in both air conditioned and non-conditioned areas
- Will increase comfort during colder seasons
- Reclaims potential storage space, protecting items from excessive heat
What To Look For:
Radiant barriers come in rolls of thin, highly reflective material, usually over 90% aluminum. The reflectivity of a radiant barrier should be as close to 100% as possible, and the emittance level should be close to 1-3 %. This means that less thermal radiation is emitted, and the heat from the roof will be reflected back. Look for a barrier with a denser, heavier weight and tensile strength – preferably one that has a woven fiber to prevent ripping and tearing upon installation. It will also discourage rodents from nesting, because they can’t use it for nesting materials.
There are so many benefits to installing a high quality radiant barrier in your home that many communities actually require it. In moderate zones it won’t have the money saving capabilities of colder and hotter climates, but a radiant barrier is a good investment wherever you make your home.
Radiant barriers have been tested by:
Oak Ridge National Laboratory
Florida Solar Energy Center http://www.fsec.ucf.edu/en/publications/html/fsec-en-15/
U.S. Department of Energy http://sigmalabs.squarespace.com/storage/reference/DOE%20Radiant%20Barrier%20Study%202012.pdf