Some of these types of roofs use materials made from clay, metal and stone. You would typically find these types of roofing materials desirable if you reside in a warmer climate with more direct sunlight, and thus higher heat indexes. By keeping solar absorption low while maintaining a well insulated attic space, the less you would need to rely on some type of air conditioning to cool the structure. While material and installation costs of these materials is usually higher than that of the traditional wood or asphalt shingles, the environmental and durability aspects are better. The initial and maintenance costs for a metal roof, for example, generally are higher but will usually last 2 to 3 times longer than its wood counterpart. The energy savings associated with these roofs over time also help to reduce the costs over its lifespan. The metals used can also be recycled or made from recycled components which help from an environmental standpoint. Asphalt shingles are petroleum based products which require more energy to produce and have no real recyclable value. Asphalt does have some upsides when used in colder climates to assist in reducing heating costs, as it absorbs heat to help raise the temperatures within a structure.
A heat sink on the Roof?
Ballasted roofing is made from placing river-rock over a synthetic rubber (EPDM) membrane and rigid insulation on top of a metal roof. This combination of materials utilizes its mass to act like a heat sink and simulate the performance of a cool roof, as it has high solar reflectance and high thermal emittance. This is the type of roof you would find on larger commercial building due to the weight. A ballasted roof will have a minimum weight of 10 pounds per square foot once it is completed. Studies have confirmed that the roof system’s mass acts as a shield protection the building from solar radiation that reduces peak temperatures and also delays potential heat flow into the building so that more of the cooling load can be moved to off peak hours of the day.
So as I discussed n our previous blogs, the world’s population is continuing to grow at an astounding rate. With this growth, come more construction, more energy use, and more landfills. While the construction will be needed to keep up with the growth, the energy use and landfill problems can be confronted and dealt with by engineers utilizing these newer technologies and materials as we move forward.