Driving to Green Buildings:
The Transportation Energy Intensity of Buildings
This summary is a shortened, condensed version of the Full Article.
Executive Summary
For an average office building in the U.S., 30% more energy is expended by workers getting to and from the building than the building itself uses. For an average office building built to modern energy codes, more than twice as much energy is used by commuters than by the building itself. This data suggests that much more focus should be put into where we locate buildings and how strongly we encourage alternatives to single-occupancy vehicles, including public transit, walking, and bicycling. This article introduces the term “transportation energy intensity” as a metric of building performance.
Multiple factors affect the transportation energy intensity of buildings. Most experts put land-use density near the top of the list of measures for reducing vehicle use; greater density makes walking feasible and public transit cost-effective. To achieve high ridership, transit needs high frequency and stops that are convenient to where people live and where they work. Raising the cost and reducing the convenience of parking encourages alternatives to car use. Mixed-use development, with residential, commercial, and retail uses permitted in an area spaces allows people’s everyday needs to be met within easy walking distance of their homes and workplaces.
Increasing the walkability of an area is key to reducing transportation energy intensity; traffic-calming measures, pedestrian-friendly streetscape design, and a well-connected pedestrian-pathway system all contribute to that effect. Encouraging bicycle accessibility with bicycle lanes and covered storage areas as well as changing and shower facilities at work encourages this non-polluting mode of transportation. Finally, improving the energy efficiency of all transportation options should remain a goal when considering ways to reduce the transportation energy intensity of buildings.
Metrics for quantifying the transportation energy intensity of a building should be developed and used to inform project development. This will help change the perception that location efficiency is beyond the scope of a particular building project.
DISCUSSIONSReader-contributed comments related to Driving to Green Buildings: The Transportation Energy Intensity of Buildings - EBN: 16:9. Comments are listed with newest at the top.
Greening the Trip to Greener Buildings
Posted by Hal Levin on Sep 13, 2007, 07:28 PMGreat job, Alex! Thanks for the careful, thorough discussion and especially thanks for your advocacy of the "high road" in terms of the need for performance-based criteria for LEED points and for putting building environmental performance in the context of transportation in the communities in which they are located.
A life cycle assessment (LCA) of suburban and ex-urban "eco-villages" full of advanced energy design houses in southern Finland found them to be more environmentally harmful than more traditional housing in Helsinki. Commuting impacts including vehicles, roads, and fuel accounted for the difference.
I would extend your suggestion beyond building and related transportation energy to include indoor environmental quality as well. Prescriptive standards based on qualifying for CHPS listing or SCS or GreenGuard certification is oversimplifed and does not do justice to the really good products that go far beyond passing the requirements to be listed and certified.
The prescriptive approach lacks the site and building specificity that is what good 'design for environment' is all about. LEED should move toward a performance-based approach for all that it rewards, mandates, or penalized. Post-occupancy evaluation and performance verification should be required.
To your data on transportation and building energy use, I would add that more than 80% of U.S. office workers drive to work in single occupancy vehicles (according to the U.S. Census Bureau). Your comparison of the SUV with five passengers to a Prius with one is an important illustration of the need to focus on the details of energy use. The same applies to energy performance measured in Btu per square foot per year. A 5,000 sq ft McMansion with 2 occupants and a 1,500 square foot tract house with 7 occupants look very different when occupancy is considered in assessing energy performance. How about source energy consumption per occupant hours per year as a new energy performance metric? Could be in addition to or instead of Btu/sf-yr.
I have analyzed the relative magnitudes of commuting and building energy intensity for a well-known, environmental award-winning office building on which I consulted in the SF Bay Area. I found that auto use for commuting requires more source energy than the office each day. Autos emit more pollution and closer to the human population than most power plants. Some of our worst air pollution exposures daily are when we are in motor vehicles on busy roads.
My PV installation and solar hot water heater make my home and home-office close to energy neutral, but one auto trip downtown uses more source energy than my house/office would use without the solar inputs.
I have analyzed the relative magnitudes of commuting and building energy intensity in the SF Bay Area and found that in general, moderate auto use for commuting to a well-known, environmental award-winning office building on which I consulted uses more source energy than the office each day.
My PV installation and solar hot water heater make my home and home-office close to energy neutral, but one auto trip downtown uses more source energy than my house/office would use without the solar inputs.
Let's work together to make our environmental performance criteria more meaningful, whether in LEED, GreenGlobes, SBTool, CASBEE, Cradle-to-Cradle, or wherever.
Hal Levin
Building Ecology Research Group
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Thoughts on Reducing Driving
Posted by Jim Newman on Dec 11, 2007, 05:26 PMBion's note about "unpredictability" seems like very fertile ground for investigation.
From Bion Howard:
"Density versus VMT -- in my graduate stats class R-sq. of 0.22 was considered non correlating, but there is a "shape" to data -- less residential density MAY cause increase in VMT, but main increase is in the unpredictablilty of the relationship. Either more data is needed or avoid a conclusion.The fact that transportation costs are a huge propotional share of overall worker expense is not a surprise, but rather it fits with other parts of the pattern. Worker productivity costs can be orders of magnitude higher (in once case Univ. Mich said 100:1 c. 1993 but I have trouble with that gap) than the operating (energy, water, etc.) costs of the office building. "
I may be reading his note incorrectly, but...
Following two threads in the comment leads to the idea that increasing the predicability of transportation needs ( or decreasing the effect of unpredictability) can have a very positive impact on transportation energy intensity in whatever measure seems to make sense.
Thread 1 is the issue that worker productivity is so much more important than resource consumption to organization finances. I expect that workers (and families and such) innately understand this, both for their organizations and for themselves. Think of your decision to drive the kids to soccer practice so that you end up with time after practice to share a family dinner instead of eating on the run. This is a productivity issue.
Thread 2 is the idea that the location of activities that MIGHT fall into a daily routine is such (in locations like Annapolis, as described by Bion) that the POTENTIAL for an unanticipated change in the daily routine activities drives the internal calculation that the resource consumption of driving is much less expensive (to the individual, to the family, to the company) than the EXPECTED time lost of these POTENTIAL activity changes. In other words, the fact that you MAY get a call from your husband asking you to grab a bottle of wine for tonight's dinner on the way home (such a call might actually happen only once every two months) means that is always makes more sense to drive to work, because you can grab that wine if you take public transit, and you never know when that call might come. And grabbing the wine is increasing your personal productivity - ie., better family interactions.
All this leads to the conclusion that what transit oriented development really means is reducing the effect of unpredictability on routine travel.