Concrete’s relatively light colour has several important environmental benefits, particularly in urban areas, helping to keep our cities cooler and to reduce energy consumption.

Bryan Perrie, CEO of South Africa’s Concrete and Cement Council.

According to Bryan Perrie, CEO of South Africa’s Concrete and Cement Council, the two primary benefits created thanks to concrete’s light colour are:

  1. Reduced lighting energy consumption.
  2. Decreased “heat island” effect in cities and built-up areas.

Both factors make a sizable contribution to helping combat global warming,” Bryan states. “In the first instance, the light colour of concrete provides a safer environment while enabling the lighting requirements in towns and cities to be reduced, both internally and externally.

“For concrete roads or parking areas, research in the USA has shown that surface reflection readings on concrete pavements and other surfaces are four to five times higher than other road surface materials. This means increased visibility for drivers and increased security in urban areas. Similar research has shown that the increased reflectance of concrete roads calls for fewer lighting masts and up to 24% lower energy requirements. This principle also applies to urban areas and car parks.”

Reducing heat islands

Explaining the benefits of the light colour of concrete in reducing the heat island effect, Bryan says on hot summer days, ambient conditions in urban areas can be to 2 to 6 degrees Celsius warmer than the adjacent countryside, thus making built-up areas “heat islands”.

These urban heat islands can influence rainfall patterns with higher rainfall downwind of cities compared to the upwind areas. The reflectance ratio – known as the “albedo effect” – of reflected solar radiation to the amount that falls on the surface, rates from 0, when no incoming radiation is reflected, to 1, when all incoming radiation is reflected. The lighter the surface colour, the more solar radiation it will reflect and the less heat it will absorb. The solar reflectance of concrete varies between 0.2 and 0.4, compared with asphalt’s much lower reflectance that ranges between 0.05 to 0.2.

“Exposed building materials with a high albedo reflect more heat and lead to cooler cities, says Bryan. The average albedo of normal concrete is about 0.35 with reflectance values as high as 0.7 to 0.8 for white concrete made with white cement. In contrast, dark materials, such as new asphalt, can have an albedo or reflectance capacity as low as 0.05.”

Incorporating albedo concrete products in surfaces

“The incorporation of high albedo concrete products in exposed surfaces, such as roads and parking areas, can significantly reduce the heat island effect and lead to cooler urban areas. In Arizona, for example, the summer temperatures of adjacent concrete and asphalt roads were measured and concrete was a staggering eleven degrees Celsius cooler,” Bryan adds.

He says using concrete, with its high heat reflectance ability, can lower average summer afternoon temperatures in surrounding buildings by as much as three degrees Celsius, cutting air-conditioning usage by as much as 18%.

“The potential increase in cost during the design and construction phases of a green structure will generally be more than offset by the savings from reduced energy usage when concrete structures are used. Life-cycle cost analyses have shown that, because of concrete’s durability, the whole life cost of many projects is lower when concrete is used as the major construction material,” concludes Bryan.

For more information, contact CCSA:
Tel: +27 11 315 0300

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