The building industry has paid scant attention to where we locate buildings or to the amount of energy used in getting to and from our buildings — whether they be schools, office buildings, homes, restaurants, or retail stores. For years, the energy intensity of a building (energy consumed per square foot per year) has been a useful calculation for evaluating and comparing buildings. Unfortunately, there is not a comparable metric for transportation use.
A close approximation can be created using federal government data on commuting workers: their average distance to work, mode of transportation (76 percent single-occupancy vehicle), average fuel economy of vehicles (21 mpg), and building square footage per office worker. This data yields the average energy use for transportation for an office building per square foot of space.
Using these admittedly crude assumptions, office-building energy use for commuting averages 121 kBTU/sf/yr. The U.S. Department of Energy reports that the average energy intensity of office buildings is 93 kBTU/sf/yr. In other words, it takes 30 percent more energy to get to and from our office buildings than the buildings use directly. If we make the same comparison using a new office building that is built and performs to modern energy codes, the transportation energy use exceeds direct building energy use by more than 200 percent.