Researchers from Singapore-Berkeley Building Efficiency and Sustainability in the Tropics, or SinBerBEST — a research collaboration effort between universities in Singapore and UC Berkeley — released guidelines April 24 for building ventilation, which aim to reduce indoor exposure to COVID-19.

The guidelines are based on research conducted in Singapore and are intended to be used in tropical areas. Efforts to produce these guidelines were led by campus associate professor of architecture Stefano Schiavon and SinBerBEST program director Zuraimi Sultan.

“The way buildings have been ventilated, especially in tropical environments where there is heavy dependence on air conditioning and buildings use mostly recirculated air, we suspect that this has implications on how COVID-19 is being transmitted,” said campus electrical engineering and computer sciences professor Costas Spanos, who was involved in this research.

These guidelines propose implementing various measures, such as opening windows, that will reduce air recirculation and increase the amount of outdoor air entering buildings. The guidelines also recommend decreased use of air conditioners when possible and adjusting air conditioning settings to maximize outdoor air intake.

Other recommendations include implementing portable air cleaners, installing high-density filters and using ultraviolet germicidal irradiation to clean the air.

Regulating building ventilation can also be a factor in determining the appropriate degree to which people should physically distance in indoor settings, according to the research.

“People are talking a lot about social distancing like 6 feet or 2 meters apart,” Spanos said. “Airflow pathway via distribution plays a role in that, and depending on the positioning of the way the air is introduced in the rooms, this distance might be different — might be more, might be less — and there’s some simple rules around that.”

The guidelines acknowledge that the degree to which the coronavirus is airborne may be relatively small, and the authors advised people to prioritize mitigating the disease’s spread through limitations of physical contact above airborne precautions.

“Diluting indoor air with increased intake of outdoor air would help even if much of the transmission is by respiratory droplets that are also in the air for a while,” said campus environmental health sciences professor John Balmes in an email.

These guidelines can be used for commercial, institutional and residential buildings, and commercial buildings can implement them relatively easily, according to Spanos. Improving building ventilation can come with some trade-offs, however. Such measures often result in additional costs and greater energy consumption.

Taking this into account, the authors suggested that people follow these guidelines when they are “technically, environmentally, and economically feasible.”

“They’re not extreme,” Spanos said. “These are guidelines that can be easily applied. The cost is in energy efficiency, really.”