CMTA Consulting Engineers: Center for a Sustainable Future
New construction of an educational facility.
Engineering firm: CMTA Consulting Engineers
2014 MEP Giants rank: 55
Project: Center for a Sustainable Future (NetZero Energy School)
Address: Adrian, Mich., U.S.
Building type: Educational facility
Project type: New construction
Engineering services: Automation/controls, commissioning/retro-commissioning, electrical/power, fire/life safety, HVAC/mechanical, lighting, energy/sustainability, plumbing/piping, and other
Project timeline: 3/12/2012 to 6/10/2013
MEP/FP budget: $1,385,972
The Lenawee Center for a Sustainable Future (CSF) is certified LEED Platinum and is the first LEED Platinum K-12 school in Michigan. During design, this goal presented a number of challenges. Input on LEED related items was required from all members of the project team very early in the design process to carefully balance architectural and civil engineering goals with MEP goals. This helped to maximize the possible LEED points. Light Pollution Reduction (SSc8) was particularly difficult to achieve due to the restrictive LEED site boundary required to maximize other sustainable site credits. The rural classification of the site also complicated this effort. The requirement for a cold climate greenhouse affected the CSF design in multiple ways including energy consumption, control techniques, and energy modeling accuracy. This portion of the building is critical to the activities and curriculum of the CSF. Tubular daylighting devices are a great way to implement energy-saving strategies through daylighting while also increasing the aesthetic of the classroom environment. In a cold climate these devices can affect HVAC energy performance. A catchment system collects rainwater runoff and stores it in a 10,000-gal underground storage tank for nonpotable use inside the building and irrigation outside of the building. Design and implementation of a rainwater catchment system is always challenging and can often be subject to varying local codes. The project team experienced some difficulty in getting this system approved for nonpotable water use inside the building. One of the energy-saving tactics for the CSF involved total plug load control. All receptacle loads throughout the building are routed through a relay control panel, which ensures that idling appliance loads are eliminated when the building is unoccupied. This required careful coordination to ensure that certain loads are not inadvertently shut down. At the time of design, the local utility company offered a pilot program for photovoltaics (PV) owners that would have reimbursed the owner at a much higher rate for any kWh generated. One of the requirements for this program was that the PV be on a separate utility meter. However, admission into this program was extremely limited and only offered by lottery on occasion. This presented unique challenges for tie-in of the PV system. A big goal of the school district was to integrate building design with the educational curriculum of the CSF. Students were involved in several meetings prior to and throughout design of the building. An energy dashboard located in the lobby helps to explain building features.
As a net zero energy (NZE) project, the building was designed to consume the absolute minimum amount of energy to reduce renewable energy costs. An NZE design greatly facilitated the firm’s ability to achieve LEED Platinum status. Geothermal heat pumps with a dedicated outdoor air delivery system condition and ventilate the building. An all-LED lighting design with occupancy and daylighting controls ensures optimum light levels while reducing energy consumption. Higher quantities of relatively short LED site poles were used to minimize the distance of light trespass from the site to meet the light pollution reduction credit. A radiant slab served by the geothermal system heats the greenhouse during winter months. During the summer, a natural ventilation system maintains space temperatures. The back wall of the greenhouse features an earth berm, and glazing with the highest R-value available was selected to further reduce greenhouse energy consumption. The design team also had to decide whether to allow the greenhouse HVAC systems to be controlled by a traditional greenhouse controller or the building automation system. It was decided to allow the greenhouse controller to manage these systems but to also monitor the status of these systems as well as temperature and humidity through the BAS to keep the owner informed of greenhouse operation. Special attention was given to occupancy schedules and greenhouse envelope in the energy model to ensure accurate modeling results. This was crucial to appropriately sizing the photovoltaic system for net zero offset. Special installation details were developed for the classroom and office tubular daylighting devices. Extra emphasis was placed on tightly sealing and insulating the roof curb where the tube penetrates the roofing structure. In addition, foil-faced batt insulation was added to the tubes above the ceiling to minimize heat transfer. The rainwater catchment system was initially used only for irrigation, but after a lengthy review by local code officials, it was decided that the system could be tied into the building and used for nonpotable water only if colored dye was added to the system. Also, the underground storage tank had to be positioned very carefully on-site in relation to the geothermal well field to alleviate groundwater contamination concerns. A careful walk-through was conducted by the contractor and owner prior to activation of the plug load control system to ensure that refrigerators and other 24/7 loads were not turned off by this system. Also, no greenhouse receptacle circuits were routed through this panel. The large ground-mounted PV array adjacent to the CSF is served by an outdoor electrical distribution panel connected to the main building. Empty underground conduits were provided between this distribution panel and the utility transformer so that the utility connection could be easily changed if the CSF were admitted to the utility pilot program at a future date. The main mechanical room has view windows, and all piping and conduit is color coded and labeled. Many elements of building systems are fully visible for educational purposes.