Research Shows First Glimpse of How Moisture and Humidity Affect Mold Growth on Buildings

Brent Stephens, civil, architectural, and environmental engineering department chair, associate professor of architectural engineering, and director of the architectural and environmental engineering programs at Illinois Institute of Technology, recently published an article with several co-authors in Nature Communications titled “Microbial and Metabolic Succession on Common Building Materials Under High Humidity Conditions.” 

Stephens partnered with a team of microbial ecologists from the University of Chicago, Argonne National Laboratory, and San Diego State University, and with chemists at Northwestern University, to investigate the microbial and chemical dynamics of mold growth on common building materials when maintained at high-humidity conditions. Stephens also collaborated with Dan Zhao (M.S. EE ’14, Ph.D. candidate), who was responsible for leading the laboratory tests. 

The team’s research provides insights into how microbes and metabolites interact over time on wetted building materials and influence mold growth. Stephens reports that wet materials experienced higher growth rates but lower fungal diversity, indicating that specific fungal taxa had preferential growth over others upon wetting. “Depending on the building material, and whether materials were tested under wet conditions or just high-humidity conditions, we saw a difference in the types of microbes that flourished on the surface,” says Stephens, pointing out that, “certain [microbes] are harmful to health and can release microbial toxins into the air.” 

He notes that the location of the materials on the building also influenced growth of microbial communities, suggesting that fungal communities that settle in buildings—which have been shown to be driven largely by outdoor fungal communities—may influence community structure upon experiencing wetting or high-humidity conditions. “Thus, we may be able to infer important information about the potential impact on human health and remediation strategies,” adds Stephens.

As stated in the published article, “Although fungal growth on building materials has been studied for decades, only a limited number of studies have used molecular techniques to investigate bacterial and fungal growth, microbial community dynamics, and metabolic activity on common building materials exposed to liquid water and/or high-humidity conditions.” 

Stephens says researchers are only now beginning to understand the fundamental chemical, biological, and molecular drivers of how and why mold grows. He shares, “It’s the first time that this big suite of modern analytical tools has been used to investigate mold growth on building materials. Up to this point, such in-depth literature had not been driven by microbiologists or chemists to examine species of mold and how they might compete with bacteria.”

Stephens describes this research as the first stage in understanding how microbes compete on surfaces and why. He says, “Our long-range goal is to understand when buildings get wet, could we actually predict which microbes will flourish and thus result in health problems?”

This project was funded by the Alfred P. Sloan Foundation’s program on the Microbiology of the Built Environment.