HVAC, COVID-19, and the Workplace

ASHRAE released a position document on infectious aerosols that suggested HVAC modification options based on Center for Disease Control (CDC) guidelines. These options can be summed up by air dilution, temperature and humidity control, and air cleaning as described below: These options can be summed up by air dilution, temperature and humidity control, and air cleaning as described below:

• Increasing your outside air ventilation can decrease the amount of recirculated air in your building. This can be accomplished with changes to your building HVAC controls to increase minimum ventilation (Assuming your Cooling and Heating Coils can accommodate the added outside air load) or night purging with fresh air of your building.
• Provide tighter control of temperature and humidity in the building. ASHRAE Data (Taylor and Tasi 2018) suggests that controlling relative humidity reduces transmission of certain airborne infectious organisms.

• Increasing your ability to clean the air by increasing your air filter efficiency (MERV) rating to minimum Merv 13 (Assuming your System Fan can accommodate the added resistance of a more efficient filter), adding portable room air cleaners, or adding duct mounted devices can help clean the air that is recirculated in your building. Other possible air cleaning strategies include installing an Ultra-Violet Germicidal Irradiation (UVGI) on the discharge side of a cooling coil kills bacteria that tend to form on coils. However, UVGI lights are not effective on Virus’s. A Bi-Polar Ionization device in your system inserts a positive ion onto small dust particles and causes them to cling onto other dust particle, thus forming large enough particles for the MERV 13 filter to effectively capture. In addition, they have been proven to effectively sterilize Virus (including Covid-19) rendering them unable to reproduce.

Which option is best for you? What are the costs to implement the above?

This depends on what system you have, what is applicable, and what works best for the way your office operates. When designing future workspaces, these same options above can be implemented at the beginning of the design process for approximately $350/ton of HVAC cooling. Including multiple options early on and having the equipment that will have the capabilities to respond to emerging situations will only help to better protect you and the people you work with. We would suggest clients speak to a trusted Professional Engineer to determine the costs and system modifications that would bring the most value for their conditions.

In summary, there is not a one size fits all, but your HVAC system can play a critical role in providing a healthy building for everyone that occupies the space, ultimately creating a safer environment to work in.