JJC Opens First LEED-Certified Community College Greenhouse

If it could, a leafhopper that sneaks through the roof of Joliet Junior College’s (JJC) new Greenhouse Facility this spring would gloat. Its lower-flying fellow pests cannot penetrate the structure: the near 16-foot walls are too high, and the passive ventilation system offers no vents or fans to slip through. But just as it prepares to dig into a chrysanthemum, that leafhopper gets sucked up and out of the facility.

The mechanically-ventilated, operable roof that ousted the pest is just one of the high-performance features of a pioneering facility that extends the reputation for innovation of JJC—the nation’s first public community college. The facility sprouts as the first community college (and second of any U.S. college or university) greenhouse to register for LEED-NC certification. Dr. James Ethridge, chair of the Agricultural and Horticultural Sciences department, expects the new facility to halve the carbon footprint of JJC’s old greenhouse.

The completely computerized facility’s energy- and water-efficient systems bring the department new ways of growing, conserving and teaching. Among its high-performance technologies are a rainwater harvesting system, a passive ventilation system and a reflective roof surface on part of the building.

Three greenhouses (warm, cool and cold) total 9,000 square feet. While one house has a black shade cloth system that creates a night setting at any time, another has high intensity discharge (HID) lights that extend the day. Ethridge says, “It gives us the flexibility to grow short day plants and long day plants at the same time.” Although the greenhouses are same size as the old ones, the department has 15% more growing space; each new house only has one walkway (versus five), leaving more room for plant benches.

The 3,000 square foot educational facility that connects to the greenhouse includes a multi-purpose classroom, a “head house” for potting, two coolers for bulb storage and a pesticide storage room.

The innovative roof offers several benefits beyond purging pests. “By eliminating traditional exhaust systems, the passive ventilation significantly cuts energy consumption,” said Legat Architects project manager, Jason Lembke. On days that are perfect for spring crops, the computerized system opens the roof to match internal temperature to outside temperature. Also, the highly reflective roof surface on the educational building reflects solar energy to reduce cooling loads.

Thermal curtains in each greenhouse further optimize temperature control. Depending on the season, the curtains—integrated with the outside temperature monitoring system—close or open to retain or keep out heat.

In the past, the JJC Agricultural and Horticultural Sciences department had to hand-water 50% of its plants. Today, most watering is automatic. The rainwater harvesting system carries all water on the roof to four underground reservoirs, then pumps it into the irrigation system for reuse. When water in the reservoirs is gone, the facility uses non-potable well water. Ethridge’s goal is to never draw from the city water supply.

A variety of technologies within the greenhouse minimize wasted water. For instance, “pulse watering” systems fill hanging pots until two minutes before water leeches out. Misters automatically stop when water reaches the capacity of a pot. “Ebb and flow” benches continuously recycle water used on plants. One system even keeps leaves a little moist, but not to the point they’re dripping. “It’s like sweat,” explains Ethridge. “By keeping the leaves misted, we’re keeping transpiration loss at a minimum.”

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