The Microbiome of Buildings, How Architecture Shapes Airborne Life

A microbial ecology and design science exploration of how indoor environments select, support, or suppress microbial communities in air

Abstract

Just as humans have a gut microbiome, buildings host a distinct ecosystem of microbes,  bacteria, fungi, and viruses,  that inhabit air, surfaces, and materials. These microbial communities are not incidental; they are shaped by architectural design, ventilation patterns, surface materials, humidity, and occupant behavior. This article examines the building microbiome as an ecological system, its influence on human health, and how design can promote microbial balance over sterility. Drawing on environmental microbiology, materials science, and building performance studies, it proposes a shift from “cleaning out” microbes to cultivating healthier microbial environments indoors.

1. Introduction

What if your building had its own microbiome,  and what if its health mattered to yours? Buildings are not biologically inert. Every wall, vent, and floor surface is colonized by microbes,  some harmless, some beneficial, some pathogenic. These communities arise from human skin, soil tracked indoors, pets, plants, and outdoor air. They interact with temperature, airflow, moisture, and chemicals. Most importantly, the microbial profile of a space influences occupant immunity, allergy development, and respiratory resilience. Unlike traditional views that equate microbial presence with contamination, emerging science recognizes the need for balance,  not elimination.

2. Where Microbes Live Indoors

Microbes in buildings occupy multiple zones:• Air – carrying microbial fragments, spores, and volatile organic byproducts• Surfaces – including walls, countertops, furniture, and flooring• HVAC systems – ducts, filters, and condensate trays act as microbial reservoirs or amplifiers• Dust – a dynamic composite of skin cells, pollen, spores, and microbial detritus• Biofilms – formed in moist zones like bathrooms, kitchens, and around windowsThe total indoor microbial load depends on ventilation, occupant density, and material choices. High humidity and poor ventilation favor microbial persistence, while air exchange and dry surfaces limit it.

3. How Architecture Selects for Microbial Life

Design decisions,  intentional or not,  select for certain microbial traits:• Smooth, sealed surfaces reduce microbial diversity and favor pathogen dominance• Porous, natural materials support richer, more stable microbiomes• Mechanical ventilation with HEPA filters lowers microbial load but may increase dryness and reduce ecological balance• Natural ventilation introduces outdoor microbial diversity, potentially enhancing resilience• Open-plan design allows greater microbial mixing; enclosed spaces compartmentalize microbiomesStudies from the Sloan Foundation’s Microbiology of the Built Environment program show that building design directly affects which microbes thrive, die, or dominate.

4. Microbial Diversity and Human Health

A diverse indoor microbiome is associated with lower rates of asthma, eczema, and autoimmune disease. Conversely, low-diversity environments dominated by a few opportunistic species may increase disease susceptibility. Exposure to environmental microbes,  especially soil- and plant-associated strains,  can train the immune system to tolerate harmless antigens and suppress overreaction. Over-sanitized buildings, particularly those with synthetic surfaces and air conditioning, may lack this diversity. The result is what researchers call a “biodiversity deficit,  ” which affects both microbial ecology and human biology.

5. The Role of Plants and Bioactive Surfaces

Indoor plants contribute to microbial diversity through their leaf surfaces, root zones, and associated soil communities. They can introduce beneficial bacteria and fungi into indoor air, modulating microbial balance. Materials like raw wood, clay, and cork also support stable microbial habitats that suppress pathogen overgrowth. In contrast, plastic laminates and metal surfaces may support biofilms if wet but inhibit microbial diversity otherwise. Choosing “living” materials encourages ecological equilibrium over artificial sterility.

6. Cleaning Practices and Microbiome Disruption

Aggressive disinfection, especially with antimicrobial agents, disrupts microbial communities. While necessary in clinical settings, such practices in homes and offices may remove beneficial microbes and select for resistant strains. Fragranced cleaners and surface sanitizers also emit VOCs that affect both microbial ecology and human respiration. A shift toward microbiome-aware cleaning,  using non-residual, fragrance-free, and minimally disruptive agents,  is essential for health-aligned maintenance.

7. Toward Microbial Stewardship in Design

Buildings should be designed not to eliminate microbes, but to host the right ones. This requires:• Ventilation that allows outdoor microbial exchange while filtering pollution• Humidity control to prevent mold while supporting mucosal health• Material selection that fosters diverse, stable microbial habitats• Integration of indoor plants and passive microbial inputs (e.g., untreated wood)• Real-time IAQ monitoring that includes bioaerosol sensing or proxiesThis vision reframes IAQ as not just chemical and particulate quality, but as a dynamic living system.

8. Conclusion

The microbiome of a building is its invisible fingerprint,  a reflection of its materials, design, use, and care. Ignoring it leads to imbalance. Cultivating it offers a pathway to resilience. As our understanding deepens, buildings will no longer be sterilized shells but living environments that partner with our immune systems. Designing with microbial intelligence means building spaces that breathe, heal, and protect,  biologically, not just mechanically.

To see how building microbiomes are being supported through design and biotic air systems, visit: www.justbreathe.in