Safety and Energy Implications of Setback Control in Operating Rooms during Unoccupied Periods

Featured Application The reduction in the minimum number of air changes and the alterations of the design temperature and relative humidity in health care rooms requiring positive pressure during unoccupied periods is allowed by the ASHRAE/ASHE Standard 170-2021 and the Spanish standard UNE 100713:2005 with energy conservation purposes, provided that the required pressure relationship or the minimum air changes required are not compromised and that the set conditions are reestablished immediately once the space becomes occupied. This work provides evidence of the savings and safety of this energy efficiency measure in operating rooms. Health care facilities are high energy-demanding buildings. The energy-saving potential is limited due to safety regulations, especially in critical care areas like operating rooms (ORs). Reducing the supply airflows during unoccupied periods, also called ventilation turndown or setback, is accepted as an energy efficiency measure as long as it does not compromise the pressure relationship. In addition, temperature and relative humidity setbacks can introduce further energy savings. This work aims at studying the effect that a setback has on the OR-positive pressure and the savings achievable in both the energy supply and CO2 emissions. Towards this target, five tests are performed in two ORs of a public hospital during the summer, winter, and midseason. A setback is applied on the basis of an occupancy sensor, and the pressure difference from the OR adjacent spaces is monitored. The outdoor and supply air conditions and airflows, as well as fan energy consumption, are measured. Punctual pressure relationship losses are observed during the occupied periods due to doors opening but not during ventilation setback operations. The energy savings achieved accounted for 75% of the natural gas consumption and 69% of the electricity in the ORs. The yearly estimations imply economic savings of near 20,000 EUR and more than 100 tons of CO2 emissions.

Automated summary

This study investigates the effectiveness and safety of energy-saving measures in operating rooms. The findings demonstrate that reducing supply airflows, as well as temperature and humidity, during unoccupied periods can result in significant energy savings.