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White paper: Raising indoor humidity to reduce the spread of pathogens

Increasing indoor humidity reduces the spread of pathogens among other health benefits

White paper summary

Compelling new research such as from the Annual Review of Virology shows that relative humidity levels of at least 40 percent can substantially suppress transmission of COVID-19, and especially airborne transmission. Yet most American buildings operate at much lower levels of humidity during the winter — usually 20 percent or less.

In this whitepaper, we explore the research and look at why most buildings have low humidity in winter. We analyze solutions for building owners and operators who want to increase relative humidity to differentiate themselves, providing healthier spaces for occupants in the post-pandemic world. We evaluate mechanical systems needed to generate humidity and their energy costs, and we use LEO A DALY’s own Vapor Drive tool to demonstrate safe or unsafe building-enclosure performance at various levels of humidity in various climates. Finally, we discuss design solutions and retrofit options for buildings of all types.