Case Study: Zero Energy

Graceland & Holabird Schools

Baltimore City Public SchoolsBaltimore, Maryland

Two Identical Schools Achieve LEED Platinum, Zero Energy, and Negative Operational Carbon Emissions

Balitmore City Public Schools (BCPS) needed to replace two aging, urban schools located 5 miles apart and close to the Baltimore Inner Harbor: the Graceland Park/O'Donnell Heights Elementary/Middle School and Holabird Middle School. The new K-8 schools were designed as 21st century learning environments, utilizing project-based learning initiatives. BCPS decided to challenge traditional sustainability and energy efficiency goals, electing to build new prototype schools that would be designed to be zero energy.

The Challenges

  • Deliver two Zero Energy schools on budget and on schedule
  • Target significant decarbonization goals
  • Create a built learning environment that provides access to building operational information within the classroom
  • Prioritize occupant comfort, health, and wellness in an urban setting
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This building [marks] a significant step in the fulfillment...of our commitment to provide our city's children with safe, modern learning environments...It is an example of our determination to press forward until every student has the tools and opportunity they need and deserve to be successful. Created with Sketch.

Dr. Sonja Santelises

Baltimore City Public Schools CEO

The Solutions

During the design process, CMTA worked closely with the architectural firm Grimm + Parker and BCPS to challenge previous ways that buildings have been designed for the school system. Through our First 30 collaborative effort, CMTA was able to drive down energy usage in the buildings by examining all energy sources. CMTA led numerous Zero Energy charrettes focused on drastic energy reduction and operational maintenance goals to allow these buildings to succeed in their first year of operation and long into the future. Based on historical project data, the decentralized geothermal water-source heat pumps with demand-controlled ventilation systems are one the most energy efficient system design approaches for K-12 school buildings. Accordingly, a geothermal heat pump system was determined to be the best solution for BCPS.

CMTA also knew that the envelope of the building, and in particular, the airtightness, is crucial in reducing energy consumption early on and maintaining efficiency and longevity. To provide a well-insulated and airtight envelope, the design team constructed the building using insulated concrete form (ICF) walls. This system combines a highly efficient thermal envelope with high density massing and an airtight envelope.

Creating a high-performance learning environment with optimal thermal comfort for the students and teachers is paramount, and the design team made sure this was not compromised for energy reduction. All occupied spaces have adjustable thermostats that allow each space to maintain temperatures between 68°F and 74°F in accordance with the ASHRAE 55 standards. Each thermostat has an override button that allows for spaces to be conditioned during unoccupied hours, as needed. Additionally, due to the school’s proximity to interstates, industrial sites, and a shipping port, the outside air system was designed with an emergency mode that closes off the outside air intakes if there is a release of hazardous chemicals or other airborne contaminants. Air intakes are located at the highest point of the buildings, reducing the exposure to ground contaminants.

The lighting system throughout the building was designed with high efficiency LED light fixtures, utilizing natural light and artificial lighting to reduce the lighting power density to 0.5W/SF. This was accomplished through reducing the overall ceiling heights in key spaces and the required quantity and wattage of light fixtures needed to achieve proper lighting levels for the learning environment.

To ensure the MEP systems continue to run efficiently for years to come, maintainability and serviceability were crucial factors in early design decisions. The team paid close attention to where and how the equipment was installed. Most equipment was kept off the roof(s) and is easily accessible and serviceable from the ground in mechanical rooms with multiple units or a single closet. The kitchen exhaust fans are the only two pieces of roof-mounted equipment. Maintaining clear roof space simplified the layout and design of the photovoltaic systems on the roof.

As an additional measure to streamline serviceability, the HVAC equipment was designed with external filter housings, and filters were standardized to 24”x24” highly efficient MERV 13 filtration. This allows BCPS maintenance staff to keep one filter size for all equipment across both schools. The Demand Control Ventilation system was designed with maintainability and serviceability in mind. This sampling-based system utilizes two high quality single CO2 sensors that sample the air of occupied spaces every 15 seconds and adjusts the ventilation accordingly. This approach requires the calibration of just two sensors for the whole school in lieu of sensors in each room.

The potential of this design's drastic energy reduction resulted in BCPS being awarded the Maryland Energy Authority Zero Energy Grant to purchase the renewable energy source for this project. The project bid within the original budget, with the renewable energy cost adding only 2.5% to the project budget. This has resulted in two, 94,000 SF Urban School Prototypes that have achieved Zero Energy and LEED Platinum Certification within their traditional project budgets.

SPHERE: An Interactive Learning Dashboard

A SPHERE Dashboard was installed to tie building features into the school curriculum. This live, interactive dashboard connects learning and real-time energy data to the built environment, allowing students and teachers to track building performance and incorporate sustainability into their curriculum. The dashboard displays the building’s real-time energy use and provides a virtual building tour for students to learn about energy efficiency and the economic impact. Due to the high percentage of bilingual students, the customized dashboard was developed to easily convert between English and Spanish.

These dashboards allow the individual schools to be used as learning labs for the district, students, and community. Rarely are facilities operated by the same owner, have identical massing, are in the same climate zone, and designed with the same MEP systems. By designing these two schools as identical Zero Energy / Zero Operational Carbon schools with only a 180-degree rotation difference, BCPS is provided a unique opportunity to use them as learning labs for the school district and design teams. This allows BCPS to make adjustments to one building—such as increased ventilation or expanded run time on HVAC equipment—and understand how this affects the performance of the building.

Click here to check out Holabird Middle Schools’ SPHERE Dashboard.

The Results

As a result of implementing energy efficient, renewable systems, the buildings have achieved an EUI of 24 kBTU/SF/ yr (Graceland) and 21 kBTU/SF/yr (Holabird)—more than a 300% EUI improvement from their average facilities. The buildings are LEED Platinum and Zero Energy certified, and they eliminate 195 Metric tons of carbon emissions per year.

CMTA was proud to partner with Baltimore City Public Schools to construct two new Zero Energy, Zero Operational Carbon schools. Not only did these schools achieve significant sustainability and energy goals, but they provided a traditionally under-served, economically disadvantaged community with two of the best learning environments in the nation.

Graceland Energy Use