Colder cities are less sustainable

Cold cities are less sustainable from an energy standpoint than cites in warmer regions, a University of Michigan researchers says. Michael Sivak has calculated that climate control in the coldest large metropolitan area in the United States -- Minneapolis -- is about three-and-a-half times more energy demanding than in the warmest large metropolitan area -- Miami. "It has been taken for a fact that living in the warm regions of the United States is less sustainable than living in the cold regions, based partly on the perceived energy needs for climate control; however, the present findings suggest a re-examination of the relative sustainability of living in warm versus cold climates," he said. For the study published in Environmental Research Letters, Sivak said he calculated the difference in energy demand using three parameters: the number of heating or cooling degree days in each area; the efficiencies of heating and cooling appliances; and the efficiencies of power-generating plants. Heating degree days are computed by comparing the mean daily outdoor temperatures with 64.4 degrees Fahrenheit; each degree above is a heating degree day, while each degree below is a cooling degree day. Sivak showed that Minneapolis has 4376 heating degree days a year compared to 2423 cooling degree days in Miami. Climate, the efficiency of heating and cooling appliances and the efficiency of power-generating plants suggests Minneapolis is substantially more energy demanding than Miami, he said. A typical air conditioner is about four times more energy efficient than a typical furnace, he said. "In simple terms, it takes less energy to cool a room down by one degree than it does to heat it up by one degree."