In her column this week, Lisa Selin Davis wrote about the optimism of those in the green building movement. Today I saw it in the flesh.

It was astonishing, the sight of more than 800 companies and organizations packed into Boston’s Convention & Exhibition Center for this year’s Greenbuild. Big guys like Honda and DuPont shared floor space with scrappier entities like Big Ass Fans and the Slag Cement Association. From the center’s (massive! awesome!) glass catwalk, I watched as attendees — estimated by one staffer to number close to 30,000 — swarmed the floor, some in suits, some in jeans, some pushing baby carriages. Venturing down into the action, I heard intense conversations about the properties of concrete and the promise of green schools and the frustrations of storm-water management.

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At 4 p.m., with just two hours until the exhibition hall closed for good, some exhibitors were showing signs of fading (“five to 10” I heard one jetlagged German staffing the booth of the Baden-Wuerttemberg economic development agency mutter), but for the most part they were going strong. Jack Orth, a green consultant and former contractor from Florida who was talking up ecoScorecard, enthused about the two big promises of the movement: jobs (and jobs that stay in the U.S.) and energy savings. Although he acknowledged that current economics are slowing things down, he expects that to change. “I see a green wave,” he said. “And when contractors tell me they don’t understand green building, I tell them they’ve been doing it for years. It’s just common sense.”

Common sense and cutting-edge design — it’s happening in ass-cold Boston this week. I’ll be back there tomorrow for more.