The application of reflective coatings or exteriors to rooftops can result in dramatically cooler interiors during hot weather, as well as an attendant reduction in energy consumption, utilities bills and maintenance costs.
Lighter-hued roofs have long been a staple of home architecture in the Mediterranean countries such as Greece, chiefly because of their ability to cool down the interiors of buildings by warding off solar radiation.
In the modern era, scientists have radically raised the ability of building roofs to cool their interiors via the development of advanced coating technology. In addition to being of a lighter colour, new coating materials possess enhanced reflectivity extending beyond the visible spectrum, as well as a heightened ability to emit energy via radiation.
The application of these sophisticated reflective coats is capable of achieving remarkable reductions in the day-time surface temperature of rooftops, with attendant benefits for building performance.
A study conducted by the cool roof division of the US Department of Energy’s Lawrence Berkeley National Laboratory (LBNL) found that even a measure as simple as a retrofitted vinyl membrane could achieve reductions in surface temperature of 24 degrees Celsius compared to the original black rubber roofing membrane of a retail building in Texas.
This dramatic reduction in roof temperatures resulted in a number benefits for the building, including an 11 per cent reduction in aggregate air conditioning energy consumption, and an attendant 14 per cent drop in peak hour demand.
These findings are consistent with research conducted by the University of Melbourne in conjunction with Dulux Group Australia, which found that the application of a cool roof coating reduced HVAC power consumption by 20 per cent at a retail store in the northern Queensland city of Cairns.
Cooler roofs also have the benefits of decreased temperatures for solar PV panels, which results in efficient harvesting of energy, as well as an extended service life for roofs themselves and reduced roof maintenance costs.
In addition to these manifold benefits, cool roofs are perhaps the easiest form of green retrofit to implement, requiring only the alteration of the uppermost portion of the exterior and entailing no interference with the structure or interior of building.
These sustainability advantages are now firmly acknowledged by construction industry standards and green building criteria, with the world-renowned LEED rating system now including a cool roof category, and the Building Code of Australia also incorporating roof reflectivity as a factor which can offset ceiling insulation requirements.