Month: December 2017

Tools for Planning a Green Community

Porchscapes is a housing project designed by the University of Arkansas Community Design Center for client Habitat for Humanity. Winner most recently of an Urban Design Honor Award from the American Institute of Architects, the project is innovative on several fronts.

The building program is for 43 single family homes that are compliant with Habitat guidelines; individual units are sized from 1,150 to 1,250 square feet.

Construction costs for the housing are low, estimated at $60 per square foot. This is because of the voluntary nature of Habitat’s building program, with future homeowners contributing sweat equity during construciton. This figure does not include Infrastructure costs.

The project, located in Fayetteville, Arkansas, is intended to foster a sense of community while simultaneously solving tricky ecological conditions unique to the site. The students and professors involved in the design have looked to the natural environment for ways to address these objectives.

Stormwater Management

The 10 acre housing site is a catchment area for water runoff from 220 adjacent acres. Stormwater surges not only cause flooding but can result in the release of toxic wastes from pesticides, fertilizers and other pollutants. To deal with stormwater runoff, the project uses a low impact development (LID) system.

Conventional stormwater management strategies are costly to build and rely on pipe and pond systems which redirect water flow away from affected sites. Using an LID or “soft engineering” approach, stormwater runoff is absorbed into the ground with the site acting like a giant sponge.

The management system includes rainwater meadows, rubber sidewalks and shared streets, all surfaces designed to be pervious to water. Pollutants are rapidly removed in the event of a storm, and water flow velocity is diminished.

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Green Neighborhood Transect and Shared Streets

In planning Porchscapes, the designers set out to build a community that would be sustainable socially, environmentally and financially. The green neighborhood transect accomplishes these goals.

Transect planning is an approach that mimics the way the natural world creates communities, with one ecosystem transitioning into another. The green neighborhood transect is composed of five elements that reflect this planning concept:

  1. House: distinguished by a compact footprint and passive design strategy to maximize the benefits of solar orientation
  2. Porch: encourages natural convection and extends the house into the adjacent green space, with the intent of enhancing social interaction among residents
  3. Lawn: rather than being a strictly decorative element, the lawn functions as part of the ecologically-based stormwater treatment system
  4. Shared Street: streets at the site are designed to slow or calm automobile traffic, safely accommodate pedestrians and cyclists, and be part of the LID stormwater management system
  5. Open Space: backyard activity is accommodated in a shared landscape to promote connections between residents

Porchscapes’ shared streets are a key component of the strategy for managing stormwater. They incorporate bioswales, sediment filters and infiltration trenches. The financial benefits are substantial: costly curbs, gutters, pipes and catch basins are eliminated, for a potential 40 percent savings, versus conventional pipe and pond solutions.

Making Low Impact Development Ordinance-Friendly

One of the most significant aspect of Porchscapes is the design team’s success in overcoming municipal engineers’ objections to the LID strategy. Sustainable approaches to urban planning often meet with rejection because they conflict with well-established practices and bylaws, or ordinances.

Under existing municipal ordinances in Arkansas, rubber sidewalks, shared streets and rainwater gardens would be considered illegal. By consulting and collaborating with the fire department and ecological and civil engineers responsible for water and utilities, designers were able to resolve planning and policy issues.

As a testament to Porchscapes’ sustainable design, the project has been selected by the US Green Building Council for LEED-Neighborhood Development certification.…