Is White the New Roof?
By Lucas on Feb 12, 2014
Image via VangViet.com
By Penny Munoz
In case you’re only tuning into the discussion now, white roofs aren’t just a trend, and researchers at Lawrence Berkeley National Laboratory are doing everything they can to prove that white is better than black and green roofs.
The pros of white roofs
According to their economic analysis, researchers were able to find two added benefits of white roofs. The overall finding was that white roofs fight climate change with greater success on a global scale than black or green because they reflect the sunlight back into the atmosphere while cooling down street levels.
In Energy and Buildings by Julian Sproul, Man Pun Wan, Benjamin H. Mandel and Arthur H. Rosenfeld, which evaluates the economic benefits of a white roof, the life-cycle costs of a white or “green” (vegetated) roof could save about $2.40 a square foot. Though not a significant amount, the environmental benefits might contribute to the appeal for some consumers.
Scientific studies have shown that per unit, white roofs are three times more effective at cooling the globe than green roofs. Similar studies have also shown substantial evidence indicating that white roofs efficiently reduce local air temperatures (commonly known as ‘urban heat island effect’). Urban heat island effect can be understood by analyzing the change in temperature between rural and urban areas. The temperature difference, is a direct result of human activity, which generates warmer conditions. In zones that have mostly black and green roofs, urban heat island effect is generally greater because these roofs absorb heat and channel it downward where there are higher degrees of movement.
The cons of white roofs
Although it is proven that dark roofs also mean higher air conditioning bills, which ultimately mean higher carbon dioxide emissions in warmer parts of the world, what does this mean for cooler regions, like Toronto?
Well, critics argue that in colder climates, white roofs can actually increase energy costs due to winter-related heating. In addition, white roofs in colder climates tend to accumulate more moisture, though there are architectural ways to minimize the impact of condensation.
A series of studies conducted by Mark Z. Jacobson and Ten Hoeve from Stanford University showed through climate simulations that though white roofs are successful in decreasing temperatures in lower parts of the atmosphere, they also decrease temperatures half a mile above ground. Why is this a bad thing? This change in temperature disrupts cloud formation, which in turn means more sunlight is reaching the earth’s surface.
What kind of roof do you have, and why? Do you think we’ll see white roofs topping Toronto soon?
