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building a greener greenhouse

When most of us think about energy efficient buildings, greenhouses do not often spring to mind.  But by taking a leadership position in the field of sustainability, the Phipps Conservatory has made the counter-intuitive idea of energy efficient greenhouses a reality.

"It wasn't our original intention to build the most energy efficient conservatory in the world, but we did," said Richard Piacentini, Phipps Executive Director, as we chatted before embarking on a tour of the world’s greenest greenhouse.

As we climbed the spiral staircase from the underground reception center to the above ground conservatory level, the pleasing wash of natural sunlight afforded by the glass dome above our heads gave way to a forest of shade as innumerable species of plants went about their glorious business of oxygenating the air we breathe at the same time they made food out of sunlight, water and carbon dioxide.

My host expounded upon the evolution of the supercentarian facility from its origin as a gift from Henry Phipps to the City of Pittsburgh in 1893, to its metamorphosis into a privately funded, non-profit in 1993, to its present status as the most energy efficient conservatory in the world, and to the anticipated construction of a new, net-zero energy building to be called the Center for Sustainable Landscapes which, by achieving a newly defined Living Building certification will exceed the U.S. Green Building Council’s Platinum LEED standard. 

"Sixteen years ago, when we went private, we realized that in order to make this a sustainable economic venture, we had to do more than put on three flower shows a year,” Piacentini said as we walked.  “We needed to increase the average visitor's length of stay to beyond the typical hour or so.  As we began to think about what we had to offer, the idea of green buildings came up.  In 1993, green building was a completely new concept, but the more we learned about it, the more sense it made.  What could be greener than a greenhouse?"

Armed with revenues from a successful capital campaign and the courage of its newfound conviction in the power of sustainability, the Phipps Conservatory embarked upon its transformation from a conventional nineteenth century indoor public garden to a fully functioning, twenty-first century laboratory and test bed for sustainable technology.

As we passed from the renovated South Conservatory to the completely new Tropical Forest Conservatory, a Siemens fuel cell module about the size of a vending machine silently reformed natural gas into hydrogen to generate electricity.  At the threshold between the old and new conservatories, a barely detectable tropical breeze wafted past us as solar-heated air ascended through the forest canopy to make its way through open panels in the 12,000 square foot glass roof, drawing cooler air from 24-inch pipes, called earth tubes, buried in the ground beneath our feet.  While the slanted, flat roof of the new structure is made of double-paned glass to increase heat retention, its serpentine vertical walls are glazed with single pane glass to permit maximum light transmission.  To avoid greenhouse heat buildup, the double-paned panels of the 12,000 square foot roof open and close.  Adjustable shades suspended from the ceiling act as solar reflectors on hot days and heat blankets on cold nights.  Operating in concert with the adjustable glass roof panels, the shades extend and retract as directed by a computerized sensing and control system that anticipates changes in temperature, humidity and light. 

In keeping with best green building practices, on days when the passive heating system can’t keep up with the weather, heat is provided by steam piped from the Bellefield boiler plant in nearby Panther Hollow.  After supplying heat and condensing back to liquid, the residual warm water is used to heat both the entry walk to the reception center and the plant beds.   “We don’t need an air conditioning system,” Piacentini explained.  “Natural convection does the job. We heat this facility for less than some people pay to heat their homes.” 

For more than a century, the Phipps Conservatory has been a place for the world to experience the wonders of botany.  Today it is also a place to witness the promise of sustainability.

And by the way, the orchids are beautiful.

This article first appeared in Tom Imerito’s TEQ column, Science Fare

© Copyright 2009, Thomas P. Imerito / dba Science Communications

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©2009 Science Communications