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How colour affects the membrane
As a manufacturer of both white and black roofing membranes, Carlisle Syntec, who manufacture RubberBond EPDM remains an advocate for careful selection of the membrane colour that is best suited for different geographies and different building types. Carlisle also suggests full understanding of the effects and properties of white roofing as a part of product selection. Far too often, a white membrane colour is selected for a building in a northern climate because of the perception that a white “cool” roof is more environmentally friendly than the alternative. However, a recent study conducted by Ashley-McGraw Architects, PC and CDH Energy Corp analyses this issue and concludes that in northern climates dark coloured roofing is more energy efficient than white roofing and more cost effective for a building owner when heating and cooling costs are examined.
The study, Comparative Roof Testing at Onondaga Correctional Facility, which is in the same ASHRAE (formerly the American Society of Heating, Refrigerating and Air Conditioning Engineers) climate zone as the majority of the UK. Found that while the reflectivity of white roofing does help keep a building slightly cooler during the summer months but the impact of white roofing on energy efficiency and heating costs during the winter months is more significant.
Many studies simply generate data based on laboratory testing and mathematical calculations. Fortunately, this study incorporates real world conditions with the most recent scientific technology and knowledge in a black roofing (EPDM) and white roofing (TPO) side-by-side comparison. To help inform and educate building owners and officials as well as design professionals – especially those in colder northern climates – they have highlighted two key figures in the study.
The study found that thermal heat loss of white roofing is 30% higher than black EPDM during the heating season. The additional heating burden this places on a building in a northern climate is thought to increase global warming by the consumption of more natural resources. The thermal heat loss played a role in 30% greater heating costs in the building with white roofing compared to the one with EPDM.
The solar absorption of a dark coloured membrane turns out to be a valuable asset in keeping a building warm during the winter months! The study also found that the cooling cost savings from white roofing during the summer months does not outweigh this figure.
It appears that selecting a membrane colour like black EPDM designed to reduce heating consumption in northern climates is energy efficient, cost effective for building owners, and good for the environment.
Speak to a member of our team for help and advice on the best solution for your flat roofing project; call us on 01494 448792 or email us at [email protected]
