Why the Transportation Energy Intensity of Buildings Matters

TOD report

Alex Wilson and Paula Melton of BuildingGreen dust off their earlier work.

Back in 2007I read an article by Alex Wilson in BuildingGreen that totally changed my thinking about green building. Wilson looked at how much energy was used by people getting to work (what he called Transportation Energy Intensity). He compared it to the energy actually used by the building (the Energy Use Intensity) and found that the transportation energy use was greater than what the building used.

The implications at the time were stunning; everybody was so proud of building LEED certified buildings in the suburbs, but when you looked at the overall impact, where the building was located had a bigger impact. As Kaid Benfield wrote about one building in Chicago:

God, where to start. What we really have here is yet another high-tech building calling itself "green" but that warrants the label only if you completely discount the sprawling, totally automobile-dependent location. Research proves that buildings in sprawling locations cause far more carbon emissions from employees and visitors driving to and from them than they save with energy-efficient building technology.

That research was probably Alex's. In the decade since Wilson wrote the original article, the concept has become part of the discussion, if not the terminology. It's there in the thinking of Transit Oriented Development and New Urbanism and Smart Growth. It is now addressed in LEED and other rating systems.

Alex Wilson and Paula Melton have now updated the original article and are much more prescriptive. They list "eight key factors that can reduce the energy intensity of buildings". A few important ones:

  • Density: The higher it is, the greater the number of options that are on the table.
  • Transit availability: This is often a function of density.
  • Mixed uses: Ellen Greenberg of the CNU says, “It’s very important for people who ride transit to be able to accomplish multiple things on foot once they arrive at their destination."
  • Parking Management: Get rid of all that free parking.
  • Walkability: A decade ago, walking was considered to be something that got you from your car to your destination. It was not really considered a transportation option. (It is still often ignored.) Now it is considered key. John Holtzclaw says, “Walkability and public transit go hand-in-hand.
  • "

So how do you turn that into a metric, into a number? It's harder than I thought it would be. But Wilson and Melton write:

....if one could define the baseline transportation energy intensity for a building type and attach a number to that, it should be possible to modify that value by a series of adjustment factors—much as is done with energy performance ratings of buildings. These adjustment factors would be based on the measures covered in this article: distance to transit, presence of bicycle pathways, traffic calming, etc. In such adjustment factors would be implicit weightings: distance to transit might be worth more than existence of bicycle racks, but both could be applied numerically.

They are not the first to try and do this; Steve Mouzon did with his Walk Appeal, as did the Institute for Transportation and Development Policy. There might even be a much simpler way, building on top of the Walkscore algorithm.

But the key point is that, no matter what metric one uses, it's important to measure. If everybody has to drive to get to a building, it's not green, whatever plaques are on the wall. It should be fundamental.