Urban Heat Island

We’ve looked at how dense urban areas compare with sprawling areas in terms of per capita emissions and we’ve also looked at whether Vehicle Miles Traveled (VMT) and gas consumption is higher in areas that sprawl than in compact areas. In both cases studies have shown what we might suspect: areas that sprawl have more climate changing emissions, bigger and less efficient vehicles.

Now how about energy use? Do compact residential communities use less energy than areas that sprawl? A study recently published in Housing Debate takes a comprehensive look at residential energy use in compact areas compared with those that sprawl.  The conclusions, again, are what we might have suspected all along. Land use policy is tantamount to energy policy. The study is worth a closer look to dig into some of the reasons this is true.

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    Thanks to The Schmidt Family Foundation / 11th Hour Project for supporting a sustainable Cascadia.

  • First, the researchers look at two factors, housing types and the urban heat island (UHI) effect.  By housing type, the researchers mean the size of homes and whether they are attached multi-family units or detached single family. UHI is the tendency for certain areas to generate more heat than others by absorbing more than they reflect. So a typical result of UHI is energy costs and demands will be higher in a heat island in summer and lower in those areas in winter.

    The study revealed that—surprise!—bigger houses consume 16 percent more energy for heating and 13 percent more for cooling. Detached houses require 54 percent more energy for heating and 26 percent more for cooling. And houses are also bigger in sprawling counties—23 percent bigger than those in more compact counties.  The Ewing index is used here to measure sprawl. Ewing takes 6 different variables including people per square mile and block size and places a threshold for density at more than 12,500 persons per square mile. (The housing data was taken from the Residential Energy Consumption Survey (RECS), the Public Use Microdata Sample (PUMS) and the American Housing Survey (AHS).  The RECS survey is conducted by the Energy Information Agency and the PUMS and AHS are both produced by the Census Bureau.)

    Overall urban form—whether a county was dense or sprawling—had a significant influence on energy use. “The average household would be expected to consume 17.9 million fewer BTUs of primary energy annually, about 20 percent less, living in a compact county,” the study concludes. Even when accounting for the UHI effect, which is greater in compact areas, a compact community would still consume less energy overall because the reduced heating demands of UHI offset the increased cooling requirements.

    In the Sunbelt, UHI tends to be a bigger problem but, overall, what the study calls the “housing effect” is much stronger than UHI. “So urban sprawl can be said to inflate residential energy consumption and associated greenhouse gas emissions regardless of location.” Hence, land use policy is also energy policy when it comes to urban forms. Compact communities encourage housing types that are more efficient and, in spite of UHI, are still more affordable to heat and cool regardless of what the weather is like. 

    Compact communities create fewer climate changing emissions, support fewer Vehicle Miles Traveled, and encourage more energy efficient buildings and homes than sprawl.  Three big reasons to sustain efforts on effectively managing growth through smart land use policy in our region.