Under the plan, all new construction at Princeton will have to use half as much energy as is required under current building codes. The plan also aims to reduce campus car traffic by 10 percent by 2020.

“We feel that we have an obligation as an institution to create an environment where students, faculty and staff can see the institution trying out new technologies … or trying to change behavior,” said Mark Burstein, Princeton’s executive vice president.

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Perhaps the biggest obstacle to creating this vision of a shining city on a green hill is that government can’t do it alone. While the city has shown willingness to lead by example, it will take the coordinated efforts of the corporate community and private citizens to turn a metropolis with an aging and underfunded mass transit infrastructure, and less-than-stellar record of water management and waste stream recycling, into a model for American cities looking to get serious about getting green.

One of the more intriguing ideas for eco-friendly urban design that Daley’s administration has tried to spread to the private sector is the green roof. Through its Green Roof Grants Program, the city has subsidized more than 60 residential and small commercial projects to the tune of $5,000 each in the last two years. Because the program includes fast-track building permits along with financial incentives, the use of green roofs has spread dramatically. In fact, Chicago now has more square footage of green roofs than any other American city.

The attraction of green roofs is that they offer environmental and economic benefits to both the building owner and the surrounding community. Cities with green roofs are more livable because the increased plant matter helps improve air quality and lowers the ambient air temperature during the hottest weather. Because plants use the energy of the sun to grow and photosynthesize rather than absorbing it as heat, green roofs help reduce the urban heat island effect (which contributes to ozone formation and increased energy consumption in the summer). Green roofs also help absorb and manage storm water runoff, which can be a big problem during heavy downpours in areas with a lot of impermeable surfaces. Owners of buildings with green roofs often see reductions in heating and cooling bills of 20% to 30%, and an additional economic incentive is a greatly increased roof lifespan. Finally, I should mention the aesthetic enhancement that added greenery brings to an urban landscape.

For those residents not willing or able to make the commitment to green roof (which may require building plans for strengthening roof support, added occupant access routes, or irrigation systems), the city recently unveiled a related intiative called the Cool Roof Grants Program. The program will encourage the use of light-colored or reflective materials, some of which use a soy-based coating, on conventional roofs. While lacking the aesthetic and water-management advantages of green roofs, cool roofs do fight the heat island effect, which means less electricity demand and better air quality. The Cool Roofs grant program will be even more well-funded than the Green Roofs program: a total of $185,000 in grants will be awarded in the first year, which breaks down to about 55 projects receiving up to $6,000 each.

Cool roofs may not be as sexy as green roofs, but encouraging their use just might be a better use of scarce municipal funds: an easily-accessible way to encourage Chicago residents to do something tangible to lower the city’s carbon footprint. In essence, this is an intermediate step toward a truly sustainable roof design, with the main goal being to get as many building owners as possible to transition away from the old black tar roofing material that soaks up the solar heat and makes the city a hotter, more smog-prone, and energy-inefficient place to live. In the age of global warming triage (change something, anything, but do it soon!), this idea makes a lot of sense for a town with the moniker "The city that works." This program will work, for the most number of people.

At least I hope that’s the impetus behind this new initiative … and not, say, influence peddling by some group of crooked roofing contractors scheming to corner the market on reflective coating materials in Cook County. After all, shadier things have happened in Chicago, and you don’t have to go back to the days Al Capone to find examples.

Photo credit: U.S. EPA

References and Resources

Mayor Daley’s Green Crusade | Metropolismag.com

History of Green Roofs in Chicago | Inhabitat

Green Roof and Cool Roof Grants Programs | City of Chicago

Chicago Green Roofs Initiative | City of Chicago

Cool Roofs | U.S. EPA

Contemporary vegetated roofs have little in common with old "earth sheltered" buildings of the 70s. A vegetated roof is an integrated system, with everything engineered for its performance in the system from the roof membranes which keep water from entering the building to the "growth media" engineered soil that sustains the plants.

But, while roofs are the easiest surface to consider greening, they aren't the only surfaces that are being greened. A number of buildings are now sporting vegetated walls, as well. And these new green walls are something more than just ivy covered buildings of yore.

The current darling of green walls is the new Museum du Quai Branly in Paris, France, a project by the noted architect Jean Nouvel which incorporates 8600 square feet of living wall with more than 170 different species. Nouvel's collaborator, Patrick Blanc has been installing his Plant Walls for more than 10 years, but the prominence of this recent project has brought a flood of new attention to the concept.

These green walls use the plants as the exterior surface of the building, over construction materials that keep moisture out of the building and retain heat in a more typical fashion. The plant material protects the building from sun and rain in a manner similar to a rainscreen.

Green walls are not only for building exteriors, either. Beamish-Munro Hall at Queens University in Kingston, Ontario, Canada has an indoor biowall to serve as a living air filter for the building to reduce CO2 and VOCs in the building's air. An indoor biowall can use a wider range of plants, since the hardiness of the plants is less of a concern inside a controlled environment.

Photo Credit: Takenaka CorporationGreen concrete is another surface greening method being developed in Japan. This system is currently being tested for steep slope embankments, where erosion would remove ordinary soils and plants. It would also be possible to build buildings with precast concrete walls which were covered with green, growing plants.

Green building surfaces allow for more plants to exist in the urban environment. They add the air cleaning properties of plants to a loaction where plants have been removed in order to build a building. Green building surfaces can provide a more amenable habitat for local wildlife. A green roof will provide more habitat for insects and birds than a conventionally constructed roof. Green roofs help to slow water runoff from buildings which would otherwise go into storm sewers. They also reduce heat island effect and aid in making cities a little bit cooler in the summertime. Green surfaces aren't a requirement for a building to be green. But they can certainly provide a number of benefits, from the aesthetic to the practical.