Project Overview
Ray Braswell High School is a 450,000 square foot public school building.
The goals of the construction project focused on both sustainability and cost-effectiveness. RWB took on the challenge, providing the design for a highly effective centralized geothermal system.
As a result, Braswell High School had the lowest energy use per square foot per year in the district in the first 12 months of operation.
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K-12 education facility
- New construction
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450,000 square feet
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Designed in Revit MEP
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Architect: VLK Architects
Project Details
On November 5th, 2013 voters in the Denton Independent School District gave their stamp of approval on major expansions in the district. The largest project in the package was the construction of Braswell High School, a new school.
Denton ISD’s other high schools – Denton, Guyer, and Ryan – were all at or well over capacity. The intent of the new construction served to alleviate overcrowding from nearby Ryan High and Denton High. The site for Braswell High School was on the east side of the school district service area, serving the rapidly growing Little Elm neighborhood and surrounding areas. The school opened in August of 2016 with capacity for 2,600 students.
Facility Overview
The school district intended on building a state-of-the-art facility, including a new modern design look and amenities. For example, “huddle” rooms and other collaborative spaces were designed for class ‘break-outs’ for problem solving or homework completion. Multiple spaces included provisions for technology, such as USB ports for charging mobile devices. In addition, the building was designed for as much daylight as possible. This included many common spaces with expansive windows and tall ceilings.
The finished high school is 452,868 square feet in size and is planned for expansion. The facility was uniquely designed with four “learning houses”. Each wing included classrooms, science labs, technology rooms, and special education facilities so they could be stand alone with respect to each grade level. The houses were connected by large open areas for administration, the cafeteria, the library, and collaborative “flex” spaces. The school also included large areas for fine arts and athletics, designed to serve both students and local community events.
239
Ground Source Heat Pumps
300
Depth in Feet of Each Well
1,118
Individual Wells
Energy Efficiency
Achieving Sustainability Goals | Braswell High School
The Board of Trustees were committed to a sustainable building. The original project requirements were tagged with over fifty sustainable design goals, with each goal being addressed one-by-one by various disciplines. The owner opted to pursue efficiency and sustainability goals consistent with LEED Silver certification but chose not to pursue this certification.
From a mechanical perspective, the building was designed in accordance to ASHRAE Standard 90.1 – 2010 (project design started in 2013). Early discussions with the building owner concluded in choosing a geothermal, or ground source, heat pump system to serve the building. The school district had a highly successful experience with geothermal systems used on a previous middle school project.
Centralized Geothermal Design
The design was a centralized geothermal system, with larger centralized pumps serving separate well fields . This included twenty geothermal well fields with over 1,110 individual wells, 300 feet in depth.
Each centralized mechanical room has two (2) large pumps designed in parallel for redundancy each served by variable frequency drives. The pumping systems generally included two-position control valves at most heat pumps; sequenced to open upon demand when the respective pump is on, and close on demand or when the pump turns off.
Additionally, the water side design included three-way valves at the extremity of each loop. This ensures water flow for each pump and that design water supply temperature is available to the system while in operation. All water loops serve a total of 239 ground source heat pumps in the building.
Although no energy model was completed for this project, the energy use of the building was closely monitored following project completion. The geothermal system helped the school achieve the lowest energy use intensity in the district (energy consumption per square foot per year) as of the end of the first full school year of operation.
Operation and Maintenance
Geothermal System | Braswell High School
The centralized geothermal system is simple to maintain. The design team developed a prefabricated pump stand that included two (2) inline pumps stacked on top of one other. This saved valuable space in the mechanical room, and allowed technicians to service this equipment in an efficient manner with ease. One (1) pump is redundant of the other, each served by dedicated variable frequency drives, which allows for service or replacement of one pump while the other handles the load.
The piping system in the well fields and in the building were predominately made of HDPE plastic piping. The pump stand, which included pumps, minimal piping, strainers, isolation valves and related piping accessories were either made of stainless steel, bronze, brass or steel with an internal coating system to prevent corrosion and loose iron in the system. This was similar for the heat pump piping runouts. A closed system water treatment system was included in the design, but with no exposed steel to the fluid, the amount of treatment was very limited.
Makeup water meters were added to the system design for each well field. The makeup water to each well field allows the facility team to immediately identify the loss of water in a system, the signs of a leak, after which the team can search for the source and repair the leak as soon as possible.
Other Challenges
Braswell High School
With daylighting being a key priority for the owner, the mechanical team designed creative solutions to battle natural stratification when systems would operate in a heating mode. Multiple two-story, high-occupancy areas with significant glass exposures compounded the problem. The team designed perimeter slot diffusers to push airflow down into the spaces and which washed the windows with air movement to prevent condensation on the glass in the winter.
This project was among one of the first in the company which was produced fully in Revit and which fully utilized the advantages of clash detection. This required the entire design team to collaborate with one another and to keep up with daily design changes.
