Reuters: The current financial downturn could spur demand for sustainably designed buildings and communities, the chairman of one of the world’s largest green architecture firms said on Tuesday. “It’s the environmental opportunity of a lifetime,” Bill Valentine of the HOK firm told the Reuters Global Environment Summit. “And if we don’t use it now as an opportunity to make the sustainable movement not just make progress, but gallop ahead, we’ve lost our chance.” The turmoil in the …