Alfa Development did things kind of backwards at Chelsea Green, its eco-friendly condo building at 151 West 21st Street. First, they opened a sales office. Then they started construction. Next, they sold out all 50 condos. And now, as closings and move-ins are starting, Alfa gave Curbed an inside tour. But mixed-up timeline aside, the project worked out swimmingly for Alfa. Designed by Stephen B. Jacobs Group, with substantial input from Alfa's CEO and Founder Michael Namerhe chose the cobalt blue solar shades and designed the floating staircasesChelsea Green holds mostly one- to three-bedrooms, and prices ranged from $875,000 to $2.95 million. The four-bedroom penthouse on the 12th floor entered contract with a listing price of $8.33 million. Since the units sold two years ago, the prices are low compared to other new developments in the area, and Namer said he expects some owners to immediately flip the units for at least a 50 percent profit.