Sunday, December 11, 2011

Paint 'Em White

That is one item on Bill Clinton’s list of 14 Ways to Create Jobs. He is talking about roofs on buildings. Our Secretary of Energy, Dr. Steven Chu, has been talking up the clear benefits of white or reflective roofs. When making a roof material and color choice on a new building, this is a no-cost way to significantly reduce the energy needed to cool buildings. Zip. Zilch. A white roof does not cost more than a black one. And when in the process of replacing a roof on an old building, it does not cost more to install a white roof. Again, not a penny more.

In commercial buildings in the southeast, most of the conditioning load is to cool the building. Because of internal heat generation from lights, people, and machines, cooling systems are often running even whe
n it is cool outside. This is another reason why a reflective roof choice is so effective in our climate. It reduces the load of the primary mode of operation of the mechanical system.

We chose a white metal roof for our commercial building in Durham. We chose it because it looks good, because it is extremely durable, because it is a great surface for collecting rainwater that we will use for irrigation and for flushing our toilets, and because it has the highest Solar Reflectivity Index (85) of any roof that met the rest of our design criteria. Not only does this save on utility costs over time, it allowed us to install smaller systems to condition the building. Yup, the color of the roof saved us money before we received our first utility bill. Why isn’t this the primary color choice for roofs?

Pictured below: The low-sloped white roof of the ClearSense building at 502 Rigsbee Avenue overlooking Downtown Durham. The rails will support solar panels (soon to be installed).

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