Like some of the best ideas, it sounded crazy at first. The old Rosenbluth building, named for the family-owned bank that once occupied it, had been vacant for some years. There was talk of converting the 160,000 square feet of office space into a luxury highrise – the planned Mandeville Place would have soared 41 stories skyward, and featured a luxury penthouse on every floor. This was in 2005, however, and Center City’s real estate bubble was on the verge of bursting. The plans fell through, and 2401 Walnut sat, vacant, for a few more years. Finally, Philly-native Charles X. Block got his hands on the building.

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Fresh, and determined, the new face of 2401 Walnut cares deeply about the world. Photo: City CoHo

The result was the City CoHo, an industrial space dedicated to groundbreaking, green building practices. Block’s Bedrock Group retrofitted the 1920s building with energy-efficient windows and a “green roof” featuring an enormous cistern that collects gray water for flushing the building’s toilets. The group took the unusual step of laying out fairly strict rules for would-be tenants: no carpeting in hallways or other areas of high foot traffic, limited or no use of dropped ceilings (all beams and ductwork exposes), and glass walls used wherever possible to demarcate space. The reason for the Big Brother-esque micromanagement is a good one: Block had his eye on LEED Platinum certification, a measure of environmental-friendliness that requires the highest standards of sustainability and efficiency to be implemented in building and maintaining commercial or residential properties.

There were those who said Block would never find enough tenants willing to play the green game, but just yesterday, news broke that 2401 Walnut has defied the odds. The building is just about 100% rented out, a few outstanding leases notwithstanding. Tenants include a diverse group of both local and national businesses: Bayada Nurses – the home care company that became 2401 Walnut’s first tenant – The Delaware Valley Green Building Council, Curalate, Wharton, Poptent, Voith & Mactavish, Ammann & Whitney, and Ticketleap, among others.

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Alloy, Wharton College’s summer incubator for MBA start ups, occupies space at 2401 Walnut – the industrial look is a good representation of what the building’s owners had in mind for the finished spaces within. Photo: Alloy

I’m personally loving the fact that the Bedrock Group went out on a ledge and had stones enough to reject paying tenants that wouldn’t maintain an earth-happy standard. 2401 Walnut may be one lone, stumpy building in the midst of a big Center City, but I wonder if it might not be the harbinger of great things to come. The more our community embraces sustainability, the more normal these “unconventional” building requirements will seem, and the more green buildings will sprout in Philadelphia.