feb blog article

Ever wondered how the color of your roof affects your energy bill?

March 3rd, 2017 Posted by Energy Efficiency No Comment yet

Have you ever considered how efficient our roof is? A white roof will reflect most of the sunlight back into space, while a black roof absorbs most of the sunlight and turns it into heat.

The color of the roof can reduce the air-conditioning load of a one-story building by as much as 20%. It can reduce both the initial and the operating costs of an air-conditioning system. Adding extra roof insulation in lieu of a white roof is more expensive and is only a partially successful alternative, since the dark roof still heats the neighborhood. In homes and other small buildings, the air-conditioning ducts are often placed in the attic, where it is common to have 28°C air flowing in the ducts and 83°C air in the attic.

The difference between a black and a white roof can be as high as 33°C, significantly heating both the building and the surrounding environment. As a result, buildings get heated twice by black roofs — directly through the roof itself, and secondly by the increased air temperature of the neighborhood. Cities can be as high as 9°C warmer than the surrounding rural areas due to the extra absorption of dark roofs, pavements and the lack of trees. This is called the “heat island effect” and it also contributes to the pollution levels in cities.

Considering the ever growing urban area, with the city of Cape Town being a good example, the use of HVAC is critical to the operation of most businesses.

E. Leclerc is typical example in France, where they saved € 20 000 (R 276 000) on the first year, after painting 7000 m² of, their roof space to white.

Sources

https://www.linkedin.com/pulse/lhistoire-du-eleclerc-qui-%C3%A9conomis%C3%A9-20k-d%C3%A9nergie-en-son-horellou

https://energy.gov/energysaver/cool-roofs

https://greenpassivesolar.com/2015/04/white-is-the-greenest-color/

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