ASI Resellers Collaborate on Building Control System for
First Complete USGBC LEED-NC 2.1 Platinum School Campus
Adapted from article published in Indoor Comfort News, January, 2008.
ASI Controls value-added resellers Digital Control Solutions, Inc. (DCS) of Gilroy, CA and N-Control, Inc. of Northbrook, IL worked together with Val’s Plumbing & Heating of Salinas, CA to design and install the building control system for the Chartwell School, the first complete educational campus to ever earn a US Green Building Council LEED-NC 2.1 Platinum rating. The school, located in Seaside, CA, had to score 52 or more out of a possible 69 points to achieve Platinum status.
Some of the green features of the 20,000 square foot Phase 1 project include a photovoltaic array sized at 26 kW, offsetting 100% of predicted annual electricity use. Taylor Engineering of Alameda, CA used eQUEST software with the DOE-2 engine to do the energy modeling for the project, using standard climate zone 4 weather as input. According to the US EPA, who gave Chartwell School a 2007 Environmental Award for Outstanding Achievement, the solar generation will offset 54,000 pounds of carbon dioxide annually, equivalent to planting 8 acres of trees.
The only air-conditioning is in the server/computer room, the school relies on a mild coastal climate and sea breezes to keep the building comfortable in the summer. Energy efficient radiant heating embedded in the concrete floor, controlled by the digital control system, provides warming as needed. A high-performance building envelope, with facade and window selection designed to enhance daylighting, help to minimize building internal loads and deliver a high-quality learning environment. Total energy use is less than 50% of a comparable building due to the daylighting and digital control system.
Rainwater runoff is channeled into a cistern to reduce erosion and supply water for irrigation and bathroom flushing. Building material from deconstruction was milled and reused where possible. When new material was required the emphasis was to select low-emitting materials. CO2 levels are monitored and ample fresh air is delivered to ensure indoor air quality.
Some of the goals for the Chartwell School posed interesting control challenges for DCS’s Christina Jones. With most of her past projects located in or around sunny Gilroy, Chris didn’t have much experience with radiant heating systems. The need to conserve energy use required minimizing the thermal energy input to the floor slabs. Chris added Bob Pauli of ASI reseller N-Control Inc., who services the region around Chicago, to the project team in order to leverage Bob’s experience with radiant heating systems and with ASI WebLink web-based interfaces.
Bob explained that “with a net-zero requirement for site-wide energy use, there was a real emphasis on minimizing consumption for space heating. With the radiant heating system you don’t want the floor slabs reaching setpoint too early, but on the other hand we didn’t want students and teachers walking into cold classrooms.”
“We first monitored the amount of time that slabs took to reach setpoint to try and figure out some of the dependencies on atmospheric conditions, amount of sunlight, location in the building, and other factors. Then we setup a self-tuning PID loop to activate the morning warm-up sequences. The processing capability of digital controls was vital to achieving the precision needed to meet energy management goals.”
The graph on the right displays a week of trend values for Outside Air Temp (red) versus slab temperature (blue) and classroom CO2 concentrations (green). You can see a spike in heating demand on Thursday, when the outside temperature dropped by over 20 degrees and the radiant heating was called on to raise slab temperature quickly to reach setpoint. The CO2 trend shows higher than normal concentrations on Thursday; perhaps due to the change in weather the kids were kept inside, or the classroom ventilation fan was manually overridden.
Christina continues the story, “due to some larger construction schedule issues the controls portion of this project ended up overlapping with the school year. It made site visits a bit more complicated, but as a side benefit I got to see how the end-users interact with the control system. I always smile when I recall one of my first visits. I entered a classroom for younger students and the desks are all empty, the kids are lying on the floor soaking up the heat! They were fascinated by the radiant heating. Experiencing the heat helped channel their natural curiosity into tangible examples of how energy is used to provide a comfortable environment.”
“It was also rewarding to see the school leveraging the trending and reporting tools in the building control system web interface. School maintenance staff can graph things like outside temperature versus energy consumption and room temperature in the browser. Students and teachers can minimize classroom energy use as part of an integrated curriculum.”
“This was the first project where I’ve integrated a weather station into the BCS front end. The school wanted the weather data displayed along with site energy production and usage trends. We selected the Vaisala WXT510, along with Weather Display software to provide data for graphing and analysis in ASI WebLink. When we first fed weather data to the WebLink display it looked like we were at the North Pole, temperatures were all reading 32 degrees. Weather Display support connected to the PC from New Zealand, they changed units on their data feed and we started converting Celsius to Fahrenheit in WebLink, then everything worked fine.”
“On a technical level the specifications posed challenges. For final commissioning we had to trend over 500 points, including some Modbus control points, initially on 1 minute intervals and then on 5 minute intervals. The trend data had to be consistent over 2 weeks without any glitches in order to pass the commissioning tests. That was a big final hurdle having to meet these stringent requirements at the end of a long project. I was definitely nervous, but the ASI Controls system passed the test.”