pearl.jpgEvery so often, we get criticized for being too fixated on fostering compact neighborhoods. “Density goes against what the housing market wants,” say some—ignoring the fact that most downtown housing developments around these parts get snapped up pretty quickly.  Or, “Density is driving up the cost of middle-class housing,” which is simply backwards—density is a response to high housing prices, not a cause. 

So we think there are plenty of good reasons for policymakers to be favorably disposed to fostering more housing close to downtown.  But the following chart illustrates another key reason:  Living in a dense neighborhood has less impact on the climate.

Density GHG chart 250The chart was taken from this awesome 2006 article* in the Journal of Urban Planning and Development, on the total climate and energy impacts of city vs. suburban living in Toronto, Ontario.  The basic finding—living in a dense urban neighborhood cuts your GHG emissions by about 60 percent.  Obviously, it’s just one study, for one city.  But the authors took a fairly comprehensive look at energy use, and their findings are generally consistent with just about every other piece of literature I’ve seen on the subject.  Really, this is just another piece of evidence adding to a fairly solid academic consensus:  denser neighborhoods mean less climate warming emissions.

  • There’s an interesting side note to this study (well, interesting to me, anyway).  Looking only at buildings alone—that is, leaving out transportation—it looks as if greenhouse emissions per square foot of living space are a teensy bit higher in dense urban areas than in sprawling neighborhoods. I would have expected the opposite, since living in a high rise means you share walls with your neighbors, and thus leak less heat to the outside world.  But this study suggests otherwise—measured per square foot, the author found that energy consumption was pretty comparable in urban vs. suburban homes.

    However, measured per person rather than per square foot, city dwellers do far better than single family homes—mostly because people end up living in smaller spaces in the city.  And regardless, the overwhelming GHG difference between city and suburban living is in transportation.  That’s where the GHG benefits of city living really kick in.

    * Study citation:  Jonathan Norman; Heather L. MacLean, M.ASCE2; and Christopher A. Kennedy, “Comparing High and Low Residential Density: Life-Cycle Analysis of Energy Use and Greenhouse Gas Emissions“, Journal of Urban Planning and Development, March 2006, pp. 10-21.

    Photo of street scene courtesy of Gordon Price