MEP Design Drives Greater Efficiency at Austin Medical Center

The 517,000-square-foot facility, which opened this summer, is the only Level 1 trauma center in the region for adults and includes 211 patient beds, with design provisions for an additional 135 more beds in the future. As a teaching hospital for the university, the new facility incorporates medical education components that will enhance collaboration among students, medical staff and patients.

Ascension, the owner of the facility, set high standards for a design team that included WSP USA as the project’s mechanical, electrical and plumbing (MEP) engineer; and HKS as the architect.

“In the health care field, sustainability and building performance are measured by energy efficiency, while hospitals are graded on patient outcomes and satisfaction,” said Shaun Grimm, project manager for WSP. “Ascension has set particularly high standards for these objectives.”

MEP strategies to reduce and optimize energy use and water use were designed to qualify for Leadership in Energy and Environmental Design (LEED) Silver certification from the U.S. Green Building Council.

“The owner embraced the architectural and engineering practices employed in the project to support the attainment of these goals,” Grimm said.

One of the MEP challenges was Ascension’s requirement for outside air delivery to patient rooms in the typically humid Austin climate.

A typical air handling system would mix outside air with return air from the building, and then pass the mixed air through a coil in an air handling unit to cool the air to about 50 degrees Fahrenheit and lower the humidity ratio. The air would then be reheated by variable air volume units in each patient room and other occupied spaces until it reaches that room’s temperature setpoint.

“The mechanical engineering strategy at Dell Seton decouples cooling and reheating using a ‘dual-wheel energy-recovery system for patient rooms,” Grimm said. “Outside air first passes through an enthalpy wheel, where it exchanges energy with a general exhaust clean airstream coming from restrooms and workrooms in the building. This allows for the recovery of energy that otherwise would have been wasted.”

The pretreated air then passes through another wheel that continuously transfers moisture from one side of the wheel to the other, discharging the air at a lower humidity level. A final cooling coil maintains the discharged air temperature between 52 and 65 degrees Fahrenheit.

“The higher discharge air temperature provides substantial energy savings on chilled water usage and on re-heat energy usage,” Grimm said. “This approach enabled the cost-effective delivery of 100 percent outside air to each patient room without the higher maintenance or first cost of other systems, like chilled beam or displacement ventilation.”

The mechanical system design uses heat recovery chillers to recover heat from the chilled water return line, and use the compressor to drive the heat into the heating water system, reducing the temperature differential of both systems.

“This strategy reduces the load on boilers at the district energy plant, saving energy and reducing the carbon footprint of the medical center campus,” Grimm said. “It also reduces the load on the district plant and its cooling towers that would otherwise consume water to compensate for evaporation.”

The MEP design also provides a locally zoned hot water system that uses instantaneous heat exchange technology, rather than a conventional gas-fired central water heating system.

The energy model projected a 23 percent energy savings, which translates into $240,000 in energy savings per year over conventional systems.

“Overall, these MEP strategies optimize patient comfort and operational flexibility, while reducing energy use,” Grimm said.

While energy-efficient, low-maintenance LED lighting has become the standard for health care facilities, automated control has been limited due to safety concerns in patient-occupied spaces. The design team found a way to introduce these controls at Dell Seton while addressing patient concerns.

“The building management system integrates lighting control, patient tracking, departmental scheduling systems and room occupancy sensors to safely enable automated on/off lighting control and appropriate variable air volume setbacks throughout the medical center,” Grimm said.

The MEP system also provides full metering of energy consumption and natural resource consumption a daily building management system dashboard that reports and displays integrated data trends to facilitate operational performance reviews.

“Dell Seton will review energy trends with the design team to compare operational results against the energy model targets for optimization of the controls,” Grimm said.

To reduce water consumption and enhance site sustainability, the medical center’s MEP system incorporates low-water-use plumbing equipment and an air-handling unit condensate recovery system designed to produce an estimated 3 million gallons of water a year for onsite landscape irrigation.

“As health care organizations come under increasing pressure to improve patient care, outcomes and satisfaction while improving operational performance, sustainability is no longer a luxury, but a necessity,” Grimm said. “For the Dell Seton Medical Center, innovative MEP strategies are contributing to sustainability in support of the medical center’s goals for patient care and building performance.”