The Phipps: Creating Energy Efficient Greenhouses
GreenBuildTV is pleased, once again, to explore the sustainable world of the Phipps Conservatory and Botanical Gardens, located in Pittsburgh, Pennsylvania. In our first e-chat, we spoke with Executive Director, Richard V. Piacentini, exploring some of the basic issues Phipps faced when taking their historical site on a more sustainable course, beginning with the design of their LEED certified Welcome Center.
In our second echat, we are exploring the Conservatory’s sustainable LEED Platinum Production Greenhouses, complete with 36,000 square feet of energy-efficient growing space and 16 different growing environments.
GBTV: To begin, how does your sustainable greenhouse design differ from the traditional variety?
Piacentini: When we began designing the Production Greenhouse, we were led to believe that a glass greenhouse could never qualify for LEED; there was a prevailing belief that these structures were too inherently inefficient to qualify. For this reason, we chose not to pursue LEED certification at the time, but the question was still in our minds: What are the big efficiency issues with greenhouses and why are they so hard to get certified?
It didn’t take long to identify the problem; greenhouses are usually built with single-paned glass because, in the winter time, and in a climate like ours in Pittsburgh, plants need as much sunlight as they can get, and double pane glass blocks too much sunlight. The problem with using single-paned glass in a greenhouse, however, is that, in the winter, they lose a lot of heat. In the summer, we have the opposite problem; large glass buildings capture a lot of sunlight and get very hot. This is called the greenhouse effect. The traditional solution to this problem is to design a greenhouse with both high and low vents. Hot air will rise and exit via the high vents and, in turn, pull cooler air in from down below. This is called the chimney effect and it works, but never very well. Over the past 40 years, a trend developed to install large exhaust fans to blow the hot air out of greenhouses and draw cooler air in from outside; this works better, but uses a lot of energy.
As we were researching the issue, we learned about new open roof greenhouses that were being developed in the Netherlands. Instead of having vents and fans, they were designed so that the entire roof would open up when it got hot, leaving no way for the glass to trap the heat inside and essentially eliminating the greenhouse effect. It was a brilliant idea, and we knew immediately that this was what we wanted to do at Phipps. Adopting this model led us to add many other state-of-the-art efficiency features, from computer controls to energy blankets, and even provoked us to take a closer look at making the plant production process more efficient. Ultimately, we earned Platinum certification for our production greenhouses under the LEED® for Existing Buildings: Operations and Maintenance program, becoming the first greenhouse in the world to do so.
GBTV: First LEED Greenhouse in the world; that’s quite an accomplishment! Congratulations. And obviously, your computer controlled weather and temperature system is at the heart of that certification. How does it work?
Piacentini: The Production Greenhouse uses an Argus computer control system that receives data from inside of the greenhouse as well as outside via an onsite weather station. The computer continuously monitors inside conditions and, in response to changes in outdoor conditions, from temperature and humidity to sunlight, rain and cloud cover, the computer automatically controls the roof vents, fans, heating, misting, energy blankets and shade cloths. On cool evenings, for example, the computer will tell the greenhouse to draw its energy blankets to prevent heat from rising into the peaks of the greenhouse, slowing down heat loss and keeping the heat closer to the plants. All of this automation makes for more efficient operations, and it also allows Phipps to maintain 16 different growing environments within our eight greenhouse ranges, with each space making its own adjustments according to the needs of the plants.
GBTV: And the ‘shade cloths’ – what are they and how do they work?
Piacentini: A typical shading system in a greenhouse consists of a perforated cloth called a shade cloth that pulls across the entire surface of the roof. The shade cloth serves an important purpose: In the summer, intense heat and sun levels can actually burn the leaves of certain plants, so a shade cloth can help block some of that light and heat. Our shade cloths, directed by the computer controls, draw and close mechanically on an as-needed basis.
GBTV: Water conservation and efficiency are also key elements in any sustainable plan. What are you doing in these areas?
Piacentini: Water conservation and efficiency in the Production Greenhouse are tied to a campus-wide system that uses an array of methods that all work in tandem. Outdoors, many of our spaces are organically managed, with drought resistant, local and non-invasive plants selected to minimize supplemental irrigation. In fact, we completely eliminated the irrigation system in our front lawn. Where irrigation is needed, we frequently employ drip irrigation systems, which use minimal water and are positioned close to the plant roots. Within the Conservatory and Production Greenhouse, we use high-efficiency plumbing fixtures and hand water most plants on an as-needed basis. Rainwater capture is also a key component; several of our outdoor spaces capture water in rain barrels, and our new Center for Sustainable Landscapes (CSL) facility has taken water capture and treatment to a new level, as all of the rainwater that falls on our lower site is either infiltrated or captured in 80,000 gallons of underground rain tank storage for watering plants on our upper campus. This, combined with our onsite sanitary water treatment for the CSL, greatly reduces our impact on municipal sewage treatment.
See a complete listing of the Production Greenhouses’ green features and practices.
Richard V. Piacentini has held the position of Executive Director of Phipps Conservatory and Botanical Gardens since 1994. During his tenure, Phipps launched the most ambitious expansion project in its 113 year history; a 36.6 million dollar expansion featuring environmentally sensitive design.
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All images are courtesy of Paul g. Wiegman.