Radiant barriers and reflective insulation products can earn the ENERGY STAR label (as insulation).
Radiant barriers are a metallic foil material (usually a sheet of foil alone or attached to something such as plywood or rigid foam) designed to block radiant heat transfer across open spaces. The material usually contains reflective aluminum. One side of the radiant barrier should be clean and dust free and must face an open air space for the product to provide maximum benefit. Radiant barriers are most effective at reducing cooling bills in hot, sunny climates. However, in some special cases the product can help reduce heating bills as well. Special care should be taken when installing radiant barriers to ensure that at least one reflective side of the product is installed next to an air space that will not (over time) be covered with dust. If it becomes covered with dust, such as on the floor of an attic, performance will degrade.
For more detailed information (how to install and cost data), visit these two websites:
When a radiant barrier is installed in an enclosed air space, such as in a wall or ceiling joist space, it is called "reflective insulation." When a radiant barrier is installed in this way a calculation can be made to determine the "effective" R-value of the product. Keep in mind, the calculated effective R-value of the product will vary depending on the direction of heat flow (up, down, sideways) and the size of the enclosed air space. Be aware that anyone claiming an effective R-value for a reflective insulation product is making a very specific assumption about how the products is installed and exactly how much enclosed air space is next to the reflective surface. Such claims can be very misleading. The performance and long-term cost-effectiveness of the product depends on number of factors, including where the product is installed, how the product is installed, and the amount of existing insulation currently in the home.
There are also low-emissivity paints and coatings called Interior Radiation Control Coatings (IRCCs) available that can be applied (painted or sprayed) directly to the underside of the roof decking and which behave similar to a radiant barrier. These paints and coatings can not earn the ENERGY STAR label at this time.