Green Roofs: Calculating the Benefits

by Alison Kibe

The known benefits of green roofs are nothing new; they can reduce building heating and cooling costs, aid in the remediation of the “heat island effect” often observed in cities, and reduce storm run-off. With this in mind, and perhaps putting aside risks and costs associated with green roofs, should I install one? Green Roofs for Healthy Cities, a non-profit industry association for green roof companies, strives to make that an easier question to answer via its Green Roof Energy Calculator (GREC) ( Developed by University of Toronto and Portland State University and funded by The US Green Building Council, GREC estimates annual cost and savings estimates for office and residential buildings with just a few clicks of the mouse. Continue reading

Models Reveal Climatic Impacts of Urban Expansion

by Dan McCabe

Greenhouse gases have earned a bad name for their impacts on global climate, but in modern cities, the built environment itself can contribute to climate change just as much. In order to quantify and analyze the impacts of urbanization on local and regional temperature and hydroclimate, Georgescu et. al. (2014) modeled the impacts of urban expansion in the contiguous United States in a variety of scenarios. The authors considered a range of different predicted population levels in the United States for the year 2100. Using advanced atmospheric models, they found that if no urban climate change mitigation measures were put into place by then, summertime urban-induced warming of 1–3 °C can be expected in cities, with exact values varying by location. These increased temperatures are due solely to the effects of the built environment, as simulations were run using climate data from 2001-2008 without any assumptions about future warming due to increased greenhouse gas emissions. Continue reading