HVAC controls put middle school in energy efficiency LEED®
The first thing students attending the new Twenhofel Middle School in Independence, KY, do when they arrive at school each day is watch TV. But the programming broadcast on the 42-in. plasma screen TV at the school's main entrance lobby isn't be the usual teenage fare. In-stead, students eagerly interact with a touchscreen menu to call up "Vital Signs" screens to see which grade is winning the ongoing monthly energy conservation contest. Or they might monitor the effects the previous night's rainfall had on replenishing the school's rainwater collection system. Or they might call up a "Vital Signs" screen that shows the dollar savings in energy and the pounds of power plant CO2 emissions that the school has saved through its innovative daylighting and solar PV systems.
Then, throughout the rest of the day, the students continuously refer to "Vital Signs" screens as they relate to the curriculum being taught in each class. In science, for example, they might use a "daylighting" screen to learn how the angle of the sun changes throughout the course of the year. In math, students can interact with "Vital Signs" to calculate how a 1-in. rainfall equates to hundreds of gal of water harvested from the building's roof for low flow toilets, urinals, and other gray-water uses.
"Twenhofel is unique in that the building itself has been designed to serve as a teaching tool, where students can see how a building functions and the enormous effect they have as occupants on its performance," said Robert Lape, facilities director for the Kenton County Schools System, one of the largest in Kentucky. "We call it a ‘high-performance' school, where students can excel through an enhanced environment, while at the same time reducing the total energy and life-cycle costs to the school district by meeting and exceeding LEED® certification requirements."
CHECKING THE ‘VITALS'The Vital Signs capability is just one of the school's many features designed to earn rating points with the USGBC's LEED system. In the case of Twenhofel, the building has been designed to earn anywhere from 33 to 38 points on the LEED certification scale, ultimately qualifying the school as Kentucky's first LEED Silver-certified school.
Innovative Energy Solutions (IES), Hamilton, OH, was selected as the systems integrator for the project, responsible for designing and integrating the school's advanced Invensys I/A Series® energy management and control system, and for the creation of the Vital Signs screens.
"With the features of the I/A Series System, we're able to precisely monitor, control, and measure the effects and benefits of all the unique systems incorporated into this project," said John Brofft, vice president, sales manager for IES. As an example, the "daylighting" system in each classroom uses photocells, which measure the light in foot candle levels and then activate artificial lighting only when natu-ral light isn't sufficient.
Several photocells communicate over a LonWorks® network to the Invensys control system, while Modbus® power monitors throughout the building measure the building's electrical usage to validate the effects of the daylighting system. The architects (Robert E. Hayes & Assoc.) designed the building with a north/south exposure, and equipped it with daylighting baffles, to allow the optimum level of natural light into classrooms through clerestory windows, such that upwards of 70% of the annual required light is provided naturally. This combination of innovative design and precise control typifies the school, and will ultimately result in significant energy savings.
100% SUSTAINABLE, 30% SAVINGSIn fact, overall energy consumption for the 111,000-sq-ft building is expected to be at least 30% less than a comparably sized conven-tional school building, thanks to the use of sustainable geothermal energy sources for 100% of the school's HVAC needs - and innovative heat recovery systems to minimize the heat that is normally lost from outside AHUs. The geothermal field, consisting of miles of tubing and thousands of gal of water for heat rejection and reclaim is located some 300 ft below the surface of the sports stadium.
"The use of a geothermal heat pump system to transfer heat to and from the school marks a radical departure from conventional blowers and chiller units, allowing us to achieve considerable energy savings and also better control IAQ, which is a big LEED emphasis," said Tony Hans, design engineer for CMTA Engineering Consultants, the firm that designed the geothermal system.
"Twenhofel is a shining example of how innovative building design and energy management systems can work together to enhance student and teacher performance," concluded Dr. Susan Cook, superintendent of Kenton County Schools.