Subscribe / Renew
|► Subscribe to our Free Weekly Newsletter|
|print email to a friend reprints add to mydjc|
September 25, 2003
Photo courtesy of UW/Soundview Aerial Photography
Designers sought to build a clean-looking building, without the mechanical equipment that often litters the roofline of medical facilities. To accomplish that goal, engineers placed the cooling tower and main building chiller in a separate plant and hid other mechanical devices behind vegetation.
Sometimes it’s the things you can’t see that contribute the most to the comfort, efficiency and usefulness of a facility.
This is certainly the case at the University of Washington Medical Center Surgery Pavilion, where mechanical engineers pioneered a number of innovative approaches. The design elements can be expected to greatly reduce the energy costs normally associated with a facility of this kind, and ensure the pavilion will meet the medical center’s changing needs.
Clearing the air
To control infection, the surgery pavilion does not recirculate its air. Instead, supplies come from the outside and are treated for temperature — a relatively expensive undertaking. For example, air changes must occur 25 times per hour in the operating rooms when surgery is in progress to ensure proper freshness.
But what about at night, when operating rooms may not be in use? Typically, air changes would continue at their daytime rate. At UW, however, engineers built a system where exchanges drop to about eight an hour during times when the operating rooms are normally vacant — resulting in a cost savings of about 43 percent over standard air processing approaches.
Of course, there may be times when a surgical procedure goes on much longer than expected, and surgeons need to keep the air exchanges going at high levels.
So inside each operating room is a control panel on the wall, with a strobe light that activates 30 minutes before air exchanges would drop to inactive levels. This allows surgeons to press an override button to maintain appropriate air change rates for the duration of the procedure.
Photo courtesy of CDi Engineers
The air-handling system performs fewer air changes when operating rooms are vacant.
Fans are an essential component in air-handling systems, but they tend to take up a lot of space. In critical facilities such as the surgery pavilion, fans require backups in case of failure. To obtain this level of safety, fans normally are installed in pairs for redundancy.
The surgery pavilion features a more creative solution. Its three largest supply air fans are mounted on stands that roll on special tracks imbedded in the mechanical room floor. Spare fans units are also mounted permanently on the track
If a fan fails, it can be unbolted and rolled out. The spare kept waiting in the wings can be easily rolled in, replacing the faulty unit in less than half an hour. The mobile fans therefore achieve redundancies at a significantly lower cost, and the size of the air-handling units are kept smaller, allowing a more-efficient layout of the mechanical room.
Maintaining HVAC equipment for a surgical facility can be difficult because the environment must be kept sterile. Even routine maintenance tasks require crews to gown up in hair nets, masks, booties and gloves.
To avoid this problem, engineers created a mechanical penthouse to serve the pavilion’s 11 second-floor operating rooms, a pioneering use of vertical HVAC supply, return and exhaust delivery systems.
The penthouse is where thermal units, heating coils, airflow measuring stations, controls and other equipment are located. Equipment can be tested and fine-tuned without disturbing either the operating rooms or the clean core where supplies are kept — and without requiring special clothing for workers.
The third (top) floor of the pavilion houses six procedure rooms, two imaging rooms, a surgery clinic for general and plastic surgery and abdominal organ transplantation, and a presurgery clinic. HVAC equipment serving all these areas is reached by catwalks above the ceilings, again avoiding the need for maintenance crews to suit up.
Sleek, flexible design
A key goal for the surgery pavilion was to have a clean-looking building, without the stacks, vents, fans, and other mechanical equipment that often litter the roofline of medical facilities.
Engineers achieved this effect by putting the cooling tower and main building chiller in a separate plant 1,200 feet away from the building. Water is piped underground through the existing UW tunnel system, and other mechanical devices are hidden behind vegetation. To the untrained eye, it looks as if the facility has no mechanical system at all.
Since usage patterns in medical facilities change frequently, the medical center wanted a floorplan that could be modified in the future. Engineers therefore placed all waste and vent stacks at columns towards the exterior of the building, rather than in the middle of the floor plan where they are normally found.
If the department needs to change room configurations, they will not have to worry about relocating mechanical elements, such as waste and vent stacks, when walls are moved. This should save UW money in renovation costs down the line.
The surgery pavilion is built into a hillside. Viewed from the Montlake Bridge, only one of its six floors (including the parking garage) is above ground. Several of the floors are thus situated below the city’s sewer connection.
Engineers therefore designed a system that pumps wastewater and stormwater up from the lower levels to empty into city sewers. And since the bottom floor of the garage is just a few feet above Lake Washington’s water level, dedicated pumps will go to work in the winter to ensure the structure stays dry.
Drinking water throughout most of Seattle is affected by algae blooms several times a year, and the UW area is no exception. Although the blooms are not dangerous to healthy populations, they can be a cause of concern for people with low immunity. High-tech filtration systems at the surgery pavilion remove algae in any water entering the facility, guaranteeing the utmost purity for patients.
The design of mechanical systems illustrates an important point — that with ingenuity and creativity, HVAC systems can be engineered for lasting efficiency and long-term flexibility — even for a facility as high-tech as the UW Surgery Pavilion.
Finn Jakobsen is a project manager at CDi Engineers, a mechanical engineering consulting firm headquartered in Lynnwood.