The challenge was to design a building complex, with open space and other amenities, that would transform a neglected city block in downtown Dallas into a model of sustainable construction and living practices.

The contest guidelines put hard construction costs in the range of $30 million and $60 million for the project, which would be designed to meet LEED Platinum standards and include about 500 residential units, 50 sq. ft. of arable land per unit, and about 75,000 sq. ft. of retail space.

The competition was launched in January by urban redevelopment specialist RE:Vision in collaboration with the Central Dallas Community Development Corporation and community design facilitator bcWORKSHOPS. The entry deadline was May 8; three winners have since been chosen by a six-member jury.

According to RE:Vision Dallas, judging focused on four areas, each weighted at 25% in the overall scoring: sustainability; affordability and constructability; innovation and originality; and the project’s ability to “encourage sustainable use of energy, transportation, commerce, community, and construction.”

Behind the green wall

RE:Vision has posted images of all three winners as well three honorable mentions (click here for the contest summary page). Eventually, one of the three winners will be picked for the actual project, which, the Central Dallas CDC executive director told the Dallas Observer, likely won’t break ground until after 2010.

All three winners – a project called Entangled Bank, from the firm Little, based in Charlotte, North Carolina; Greenways Xero Energy, from David Baker and Partners Architects and Fletcher Studio, based in San Francisco; and Forward Looking, from Atelier Data and MOOV, both based in Lisbon, Portugal – attempt to accommodate the arable-land requirement in fairly ambitious ways.

But as one Observer reader pointed out, growing anything but desert-tolerant succulents on the buildings’ south- and west-facing sides will be difficult because of the intensely hot Texas sun, and attempts at maintaining green-growing, moisture-retaining walls can be derailed by mold problems that are particularly tenacious in Dallas.

But the CDC seems willing to listen to good advice. And there’s plenty of time before digging starts.