From its founding in 1909, The Walter Reed Army Medical Center has served more than 150,000 military personnel. Many improvements and renovations later, it was ultimately determined that a major addition was needed to maintain quality patient care. Today, a new era has begun for the newly completed Walter Reed National Military Medical Center, located in Bethesda, MD, on the grounds of the National Naval Medical Center.

For this giant health care site, a mechanical systems giant — the Southland Industries branch in Dulles, VA — was chosen to provide Design/Build mechanical, plumbing and medical gas services. The project, procured through a Design/Build competition, included the construction of a 345-bed medical center. It provides the full range of intensive and complex specialty and subspecialty medical services, including specialized facilities for the most seriously injured.

The new facility, located at the current site of the National Naval Medical Center in Bethesda, MD, is expected to become the U.S. military’s premier tertiary referral center for casualty and beneficiary care. It will offer postgraduate education and other training, and will serve as a critical medical research center. The Naval Facilities Engineering Command (NAVFAC) oversaw the planning and construction of the project.

The project consisted of both new construction and renovation of existing buildings. Southland’s scope of work for the new construction included the design and construction of the mechanical, plumbing and medical gas systems for a:

• 533,000 sq.ft. medical office building
• 157,000 sq.ft. addition to the existing hospital
• 340,000 sq.ft. patient parking garage
• 400,000 sq.ft. multi-use parking garage and upgrades to the campus central utility plant, along with utility infrastructure upgrades and expansion to serve the added spaces.

100% Outside Air
Health care facilities present a design challenge to ensure a safe and healing environment. There’s risk of the transmission of infectious disease through the HVAC systems. Emerging issues such as drug-resistant tuberculosis and severe acute respiratory syndrome (SARS) have elevated these concerns. An HVAC system that doesn’t re-circulate the indoor air, but instead uses 100% outside air at all times will enhance the indoor air quality by ensuring that any infectious organisms in the air aren’t moved to other areas of the facility, but are instead exhausted to the outside.

The premise of the selected HVAC system allows for improved indoor air quality compared to traditional systems. Using 100% outside air means that there’s a constant influx of fresh air throughout the buildings. The project achieved a Leadership in Energy& Environmental Design (LEED) Innovation in Design credit for the 100% outside air approach as it applies to air quality. Southland implemented numerous innovative mechanical and plumbing features into the design of the project. The design consists of a constant volume HVAC system that uses 100% outside air, which helps with infection prevention, as well as pressure control within the hospital. Most traditional systems are designed with a recirculating return air system. (Additionally, one of the mandates of the request for proposal was to deliver, at minimum, a LEED Silver project. At the project’s completion, it won LEED® Gold.)

Taking this into account, an energy efficient HVAC system was designed. Large, Thermotech enthalpy heat recovery wheels recover energy from the buildings exhaust air before it’s exhausted from the building.

"A significant feature for a healthcare mechanical system is the ability to deliver and maintain the required amount of outdoor air, while meeting the project's RFP energy reduction goals," says Lead Engineer Chris Skoug. "Conventional recirculating (mixed air) systems typically fail to provide or maintain the required amount of outdoor air (ventilation) to the occupied space. This issue is compounded when using variable air volume systems to reduce energy consumption. The fundamental challenge of providing and maintaining U.S. Department of Defense Unified Facilities Criteria (UFC) required outside air to the occupied space, while reducing energy still remains difficult to accomplish in a lifecycle cost-effective manner," he says.

Multi-Stack heat recovery chillers pre-heat the building's water heating system. A copper/silver ionization system provides for Legionella control in the hospital's domestic hot water supply. Large, custom air handling units by Buffalo Air Handling, are manifolded together for redundancy and enhanced control of the indoor environment.