Enhancing sustainability

[This is the fifth in a series of blog posts by David Dixon FAIA, principal-in-charge Planning and Urban Design at Goody Clancy. Dixon's posts are part of a series of expert blogs on TOD highlighting work and research that experts are doing in the field.]

Kaid Benfield, Smart Growth Director for the Natural Resources Defense Council, studied data from metropolitan Baltimore to tease out the correlation between density and driving. Households in neighborhoods dense enough to support walkable Main Streets, he found, drive roughly one-third as many miles each year as those in auto-dependent suburbs. A study commissioned by developer Jonathan Rose demonstrates that households in urban multifamily housing consume roughly one-third as much energy over the course of a year as households in suburban detached dwellings. Such analyses make a convincing case that significant reductions in energy consumption, carbon footprints, and comparable sustainability benchmarks will require development patterns that focus growth toward infill of established urban areas rather than outlying greenfield sites.

By 2050, America will add a projected 90 million people. Accommodating a significant portion of this growth in cities to avoid sprawl will require significantly increasing density in urban neighborhoods.  Even housing existing urban populations over that period would require additional housing, because the size of individual households is declining. For example, in 2000, when growth brought Seattle’s population back to its 1960 level of roughly 600,000, the city required 35% more housing units than it had four decades earlier—to accommodate the same number of people. Seattle met this challenge in part with a five-year planning initiative that built support for a new generation of lofts and mid-rise apartments in its core neighborhoods. The increased vitality that this added density brought to languishing commercial districts helped cement popular support for the plan.

Seattle’s higher density of housing did not come at the expense of single-family houses; rather, new housing arose on brownfields, redeveloped strip malls, older industrial parcels, and similar sites that involved expensive land acquisition, environmental clean-up, and related redevelopment costs—often far in excess of the costs of making comparable greenfield sites buildable. In an era of scarce public resources, increased density is essential to support the high site-redevelopment costs that make possible an ambitious new era of more sustainable urban growth.

Next: Creating places that people love

Part 1: Density deficits
Part 2: Restoring personal choices
Part 3: Building community in the midst of diversity
Part 4: Fostering public health
Part 5: Enhancing sustainability
Part 6: Creating places that people love

David Dixon is co-author of Urban Design for an Urban Century: Placemaking for People