Large banks, the likes of Citi (C), HSBC and Morgan Stanley (MS), have been only too happy to tout their green building initiatives. At some green buildings, a massive field of grass sits atop the building, but the idea of a green wall is also in vogue. And PNC is only too happy tout its recent activity at one headquarter building in Pittsburgh.

The AP notes that PNC executives are convinced that its green wall is the largest in North America. The wall covers 2,400 square feet. The entire wall, however, requires only 15 minutes a week of watering during peak growing season and even less in winter. The wall "features more than 15,000 ferns, sedums, brass buttons and other plants" that create swirling patterns of green above the corporate logo.

The goal here, apart from good press, is to lower HVAC costs, thus benefiting the environment. PNC says it will be 25 percent cooler behind the wall than the ambient summer temperatures. A formal ROI analysis would be welcome. 

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