Colors
for Exterior Finishes
Solar heat gains
conducted through roofs can considerably increase cooling loads. Improving
roof insulation or increasing the roof reflectivity can reduce solar
gains.
Increasing the
roof reflectivity to 0.7 or more can reduce solar heat gains by 80%
compared to typical dark roofs. This can be achieved by a variety
of techniques, such as covering the exterior surface of the roof with
white gravel ballast, light-colored tiles or reflective paint.
Solar gains through
roofs can also be reduced using reflective foil radiant barriers located
in attic spaces of cavity roof systems, e.g., gable roofs. They are
proven effective at lowering cooling demand, and can be retrofitted
above thermal insulation and below the ventilated cavity.
Cautions
- Light colors
on roofs are difficult to maintain in urban areas.
- Structural
loading design must account for ballast.
- If using gravel
ballast, fit gravel stops around rainwater drains and the roof perimeter.
- Reflective
foil radiant barriers can raise attic air temperature and roofing
surface temperature dramatically, so an attic fan is usually an
important complement.
