Additional attention is focused on building ventilation as more people return to physical workspaces. Recently, the White House issued the Clean Air in Buildings Challenge, providing guidelines for ventilation, filtration, and communications. The Lab is already implementing many of the recommendations in the challenge, working with Facilities, Environment, Health and Safety (EHS), Sustainable Berkeley Lab, and the Indoor Environment Group.
This article provides some information about what the Lab has been doing to address ventilation at the Lab during the COVID-19 pandemic. To learn more please join us for a webinar on Ventilation and COVID-19 on Wednesday, May 18, 2022, at 11 a.m. Stay tuned for more information on how to join the webinar and how to submit questions in advance.
Understanding HVAC systems
Heating, ventilating, and air-conditioning (HVAC) systems both condition air in the building (providing heating and/or cooling) and also bring in outdoor air (ventilation). Typically, systems have a setting for the minimum amount of outdoor air that is intended to maintain acceptable air quality, based on the number of occupants a space was designed for. This air from the outside is mixed with air that is pulled from inside the building (recirculated air), then passed through filters, conditioned, and distributed throughout the building.
Laboratory spaces are typically designed to have 100% outdoor air (no recirculation). Non-laboratory spaces are typically designed to have a minimum of 20% outdoor air, increasing up to 100% depending on temperature conditions. In buildings without mechanical ventilation systems, outdoor air can be increased by opening windows, doors, and rollup doors.
When outdoor air is cooler than the indoor target temperature, it saves cooling energy to increase the fraction of outdoor air that is pulled in and distributed; the equipment that does this is an economizer. The vast majority of HVAC systems at the Lab have economizers that operate for much of the year, to provide very high fractions of outdoor air in an energy-efficient manner.
When outdoor air pollutants reach potentially harmful levels (as indicated by the EPA’s air quality index) – such as during wildfire smoke events – HVAC systems are set, in buildings with such capability, in a special mode of lower outdoor airflow rates to protect building occupants. In this mode, airflow through the HVAC systems continues to be passed through filtration and conditioned before being redistributed within a building space.
Some conference rooms and other spaces with highly-variable occupancy have been designed to have “demand-controlled” ventilation (DCV), which will increase or decrease the supply of outdoor air based on measured carbon dioxide (CO2) levels. The Lab is reviewing the control settings in these areas and adjusting as necessary to provide outdoor air whenever the space is occupied.
The Lab continues to implement its filter enhancement project to replace existing filters with MERV-14 filters when a particular building’s system can handle it. Increasing filtration beyond MERV-14 (or beyond what a system can handle) may restrict airflow and lead to building pressurization or heating/cooling problems.
Portable HEPA-filtered air purifiers can be used to augment existing ventilation and may be recommended for spaces with higher occupancies and minimal ventilation.
Conference rooms have been open for nearly a year for groups to use following the Lab’s COVID-19 protocols. The Lab has also put together new protocols for in-person meetings which include some previous recommendations. Although ventilation in a number of spaces was assessed when the Lab had occupancy controls in place, it is not required to have a ventilation assessment prior to using a conference room. You can check to see if your conference room has had an assessment here. Whenever possible, it is recommended to maximize ventilation by opening doors and windows, or by operating air purifiers when present.
Building Managers or other division points of contact can submit a Space Evaluation Request if they have concerns about a previously unevaluated conference room. Spaces will be assessed as staffing will allow.
To learn more about ventilation at the Lab, please join us for a webinar on Ventilation and COVID-19 on Wednesday, May 18, 2022, at 11 a.m. Stay tuned for more information on how to join the webinar and how to submit questions in advance.
By Laurel Davis, Brandon DeFrancisci, Oren Rieger, Brett Singer, and Raphael Vitti