Summary: Although buildings themselves are responsible for the lion’s share (48 percent) of all greenhouse gas (GHG) emissions annually, the impact of building design and siting on transportation patterns should not be taken lightly. A study limited to office buildings and commutes by BuildingGreen.com authors Alex Wilson and Rachel Navaro points up the impact and proposes planning and design solutions.

Environmental Business News (EBN) in its September 2007 issue features “Driving to Green Buildings: the Transportation Energy Intensity of Buildings.” The article, which calculates energy use only for office buildings and workers, figures an average U.S. commute of 12.2 miles, with average mileage of 21 mpg will use 27,700 kBtu per person over the typical 235-day work year, given established assumptions on number of persons per vehicle.

It should be noted that adding in other types of commercial buildings plus residential buildings, the overall energy consumption of these buildings is 37.7 percent more than can be ascribed to transportation overall. The more specific point the article advocates, however, is for including transportation energy intensity as a building-performance metric. According to the article, with the average office occupancy of 230 square feet per person, transportation energy use for the average office building is 121 kBtu per square foot, the EBN authors calculate, whereas the operating energy use averages 92.9 kBtu per square foot (or 30.2 percent more) for a typical office building and 51 kBtu per square foot (137 percent more) for a new building designed to ASHRAE 90.1-2004.

What’s an architect to do?
The most important elements to reducing the transportation energy intensity of a building will be through more mixed-use density, less sprawl, more use of mass transit and carpooling, and better conditions for walking and biking to work. Conceding that these issues are the purview of urban planning much more than individual building design, the EBN article still offers some building-specific ideas for transportation efficiency. Key among them is building siting.

In Portland, Ore., for instance, more than half of all development in the past 10 years has been located within one block of the city’s streetcar line, with property values 35 to 40 percent higher for those properties than those even two blocks away from the line.

Designing mid-block cut-through paths into a building will make a city more walkable. And something as simple as secure bicycle storage areas and shower/changing facilities will send the message that the building was designed with alternative transportation modes in mind.

To read the full text of “Driving to Green Buildings: The Transportation Energy Intensity of Buildings,” visit BuildingGreen.com.