From ‘green movement,’ ‘Green Party,’ ‘green collar jobs,’ to ‘Greenpeace,’ the color reference is to plants, chlorophyll, the green pigment central to photosynthesis, which is the basis of all life. Quite often, however, the chief environmental goal being advocated has little to do with plants, but rather promoting low-impact technologies, practices and lifestyles.
This is the case with “green building design” which is receiving growing attention because of the under-appreciated magnitude of building emissions worldwide. Recently, New York City audited the source of all its CO2 emissions and found that nearly 80 percent is from building energy consumption. Worldwide the estimate is closer to 45 percent, making “buildings the biggest single contributor to anthropogenic climate change – a worse offender than all the world’s cars and trucks put together.”
The vast bulk of green building design focuses on efficient heating, cooling, lighting, insulation and window technologies. All of these are great things of course, but what’s not mentioned in the Nature article is a truly ‘green’ building technology – living green roofs and living walls. These are technologies that introduce plants into building facades, especially rooftops.
Typical dark rooftop temperatures in summer sunlight can reach extraordinary levels of 150 degrees F (~65 degrees C) or more. It makes little sense not to address such an extreme building heat source in green building design. Moreover, in cities, rooftops, among other dark, impervious surfaces like streets and parking areas are a chief contributor to the “urban heat island” effect which elevates the temperature and climate in cities well above surrounding suburban and rural areas. This extra heat can be deadly during heatwaves, especially if air-conditioning is not available or fails during blackouts. Resident proximity to high-floors and rooftops was a risk factor in both the deadly 1995 Chicago and 2003 European heat waves.