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Issue link: https://mcdmag.epubxp.com/i/105316
COMMENTARY HOSPITAL HVAC ENERGY: Driving with the brakes on By Travis R. English I was recently at a seminar, learning about process mapping, six sigma and Lean tools. Our teacher taught us a technique called "five whys." To understand this method, picture my 3-year-old daughter asking "Why?" "Why?" "Why?" five times in a row until I say something exasperated like "because I said so." As a game, let's apply the "five whys" technique to my opening line: U.S. hospital buildings use more energy per square foot than most commercial buildings. "Why?" Hospitals use a whole lot of energy in HVAC systems. Anywhere from 50 percent to as much as 70 percent of energy in most hospitals goes to HVAC. "Why?" Most hospitals use a system, such as constantvolume reheat, which is inherently energy intensive. "Why?" We design hospital HVAC systems to meet airchange requirements. "Why?" The industry standards and many building codes require minimum air changes. "Why?" Air-change requirements are intended to provide comfort and prevent airborne infection transmission. There have been three recent substantial publications on energy use in hospitals: > NREL's "Large Hospital 50% Energy Savings: Technical Support Document" 60 Medical Construction & Design | January/February 2013 > The University of Washington's Integrated Design Lab's "Targeting 100! Envisioning the High Performance Hospital: Implications for A New, Low Energy, High Performance Prototype" > ASHRAE's "Advanced Energy Design Guide for Large Hospitals: Achieving 50% Energy Savings Toward a Net Zero Energy Building" The good news is these publications are all fairly consistent in recommendations. The bad news is these publications are all fairly consistent in recommendations. The typical system in U.S. hospitals is the HVAC equivalent of driving with one foot on the brake pedal. We run chillers to cool air down to where it is nice and cool and dry. Then, right before it goes to a room diffuser, we heat it back up so as not to freeze out the occupants. This has some seemingly crazy results: many hospitals run heating boilers in the middle of summer, even on days when it is 100 degrees outdoors. Ostensibly, one reason we do this is for infection control. By the U.S. standard, a patient room, for example, requires a full change of the air in the room every 10 minutes. We're not allowed to open the windows. And, at no point can we reduce the air. An architect I work with recently showed me a hospital project in Rio Negro, Colombia. The extent of the naturally ventilated area (noted as "sin acondicionado") was astonishing. The HVAC system approach was fundamentally different from DOUGLAS RAPHAEL/DREAMSTIME Consider this: U.S. hospital buildings use more energy per square foot than most commercial buildings. The U.S. Energy Information Administration's 2003 Commercial Buildings Energy Consumption Survey ranked hospital buildings at 249.2 kBtu/sf, in second place for the highest energy consuming building type. The dubious honor of first place went to food service, coming in at 258.3 kBtu/sf. But, I'll come back to food. www.mcdmag.com