Our Hidden Roommates

An interview with Dr. Sarah Haines The Indoor Microbiome is the complex, invisible world of trillions of microorganisms living within indoor environments. Its residents include bacteria, archaea, fungi and viruses. We live immersed in this ecological niche, for good or ill. A typical home can host between 500 and 1000 different species of bacteria in household dust alone, and thousands of species of mold, yeast and viruses are in the air and on the surfaces around us. Together they serve as the primary ecological interface through which buildings influence human biology. In this light, we are beginning to view indoor environments not merely as passive shelters, but as active, highly complex indoor ecosystems that actively influence our immune and endocrine function, and long-term wellbeing. Today, we are joined by Dr. Sarah Haines, Assistant Professor at the University of Toronto and Principal Investigator of the IMEE Lab, to explore the foundational framework behind this shift. We will discuss the emerging perspective of "biologically informed architectural design" and the fact that architects and interior designers don’t just curate materials, they curate our basic microbial exposures and therefore our health and wellbeing. Sarah Haines Dr. Sarah R. Haines is an interdisciplinary researcher and educator working at the intersection of building science, environmental engineering, and microbiology to investigate how indoor environments shape human health. Assistant Professor in the Department of Civil and Mineral Engineering at the University of Toronto, the Principal Investigator of the Indoor Microbiology and Environmental Exposures (IMEE) Lab and member of the Hub for Advancing Buildings . She holds a BS in Environmental Engineering and an MS and PhD in Environmental Science from The Ohio State University. Her research focuses on maintaining healthy and sustainable indoor environments through detection and characterization of abiotic and biotic indoor exposures using a variety of techniques​. She integrates community-based participatory research, advanced molecular techniques (e.g., high-throughput sequencing, digital PCR, metatranscriptomics) and filter forensics to examine microbial dynamics and contaminant exposures indoors. Her work includes studies of moisture-driven mold growth in building materials, microbial volatile organic compound emissions, and the use of filter dust to estimate airborne concentrations of contaminants and pathogens, including SARS-CoV-2. Through this research, she develops practical, evidence-based strategies to reduce harmful indoor exposures, particularly in the context of climate change and housing inequities. Prof. Haines is a member of the American Association for Aerosol Research (AAAR) and the International Society of Indoor Air Quality and Climate (ISIAQ), as well as the Institute of Health Emergencies and Pandemics (IHEP) contributing to interdisciplinary efforts that connect indoor air quality, building performance and health. She was the 2024 recipient of the University of Toronto Faculty of Applied Science & Engineering Early Career Teaching Award, recognized for excellence in teaching and mentorship. Team Hosted by Kristof Irwin Edited by Nico Mignardi Produced by M. Walker

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Our Hidden Roommates is an episode from The Building Science Podcast by Miguel Walker.

This episode is 1:03:59 long.

This episode was published on Feb 12, 2026.

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