Health-care HVAC design engineers are familiar with “the table,” a list of space types, pressure requirements, temperatures, and air-change-per-hour (ACH) rates. The table’s format, columns, and keynotes, as well as many of its entries, date from more than 25 years ago. In 1987, long before the era of sustainability and energy awareness in which we find ourselves, it appeared in the first edition of “Guidelines for Design and Construction of Hospital and Health Care Facilities,”1 published by The American Institute of Architects. Today, it is the responsibility of ASHRAE, which maintains the table as ANSI/ASHRAE/ASHE Standard 170, Ventilation of Health Care Facilities.
By requiring total ACH rates, the table encourages constant air volume (CAV) with reheat, perhaps the least energy-efficient central air system possible.2 The core principle—reheating, or simultaneously heating and cooling, air—is prohibited in most spaces by modern energy codes. California, for example, restricted CAV-with-reheat zones as far back as 1981.3 In the United States, unlike other countries, though, health-care spaces often are exempt.
This has a significant impact on energy use. Inpatient health-care facilities are the second most energy-intensive building type in the United States (Figure 1), with heating (including reheat), cooling, and ventilation accounting for 52 percent of their energy use.4
Kaiser Permanente’s Facilities Planning & Design engineers speak with many consulting engineers about health-care design. Some consulting engineers say they feel “handcuffed” by the ventilation standard (“We could achieve so much energy efficiency, if only we could change the ventilation rates”), while others believe the ventilation rates are akin to a moral imperative (“If the code says 6 ACH, anything less endangers patients”). Wanting a better sense of these engineers’ thoughts, we conducted a survey.