"Cool Roofs"
A "Cool Roof" is defined as a roof surface that has both high reflectivity and high emissivity. High reflectivity requires the surfacing material to reflect solar energy away from the surface. High emissivity requires radiating heat energy away from the surface. Roofs undergo significant expansion and contraction as they heat and cool throughout the day. Heat absorbed by the roof can also accelerate degradation by ultraviolet rays and water. A reflective roof can reduce the amount of thermal shock that occurs on the roof surface and prolong the life of the roof.
Green Roofs are considered very effective "Cool Roofs".
The Sealoflex® CT Green Roof Installation is an impervious, rubber based system. Advantages are:
-Slows water runoff, reducing dependency on retention ponds;
-Reduces heat island effect in inner city environments;
-Provides the ability to create beautiful garden environments on rooftops.
Chlorophyll found in all plant life is the most solar reflective medium known to man. Thus, a green roof in midsummer will be even cooler than a comparable white roof by approximately 15°F. To enjoy these environmental benefits and a remarkable range of design options, a dependable waterproofing system is critical. The Sealoflex® CT System with the Sealogreen™ drainage mat offers the ideal combination.
Green Roofs Technical Information
1.2.1.3 - Green Roofs Application Guide
Related to this is the concept of Solar absorptivity. Solar absorptivity is a fraction which represents the difference between how much solar radiation is absorbed by a material versus that which is absorbed by a standard black surface. Since black (dark) surfaces absorb more solar energy than lighter colors (i.e., do not reflect as much), those surfaces are warmer. Click below to see a representation of this principle.