Tag Archives: Indoor air quality

Building Ecology and Indoor Air Quality (IAQ)

Home+Ecology+Stock+ImageIt’s commonly assumed that buildings are simple, inanimate entities, relatively stable over time. This implies that there is little interaction between a building, what’s in it (occupants and contents), and what’s around it (the larger environment). We commonly see the overwhelming majority of the mass of material in a building as relatively unchanged physical material over time. In fact, the true nature of buildings can be viewed as the result of a complex set of dynamic interactions among their physical, chemical, and biological dimensions. Buildings are best described and understood as complex systems.

Research applying the approaches ecologists use to the understanding of ecosystems can help increase our understanding. “Building ecology “ has been proposed as the application of those approaches to the built environment considering the dynamic system of buildings, their occupants, and the larger environment.


Humans are covered with bacteria on all surfaces exposed to the environment around us – our skin, respiratory, and digestive tracks. Roughly 2,000 organisms occupy each square centimeter of these surfaces (roughly 15,000 organisms per square inch). We shed our outer skin layer each two weeks. The skin cells and the oils and other chemical in and on them as well the bacteria hitch-hiking a ride on them end up on the floor, furniture, and even the walls and windows.

When bacteria undergo the transformation from a nomadic life (in air) and become sedentary (settle on surfaces), “they undergo a reversible lifestyle switch.” They “…lose motility and become enclosed in a gooey extracellular matrix,” a kind of film on the surface.  There they “sense” their neighbors in the “society” where they find themselves and develop specialized strains to take on different tasks in the community where they find themselves. These evolved bacteria secrete chemicals as part of the “community”.

Of course these chemicals are not occurring independent of the conditions surrounding them, the moisture, chemicals, and particles that are also on the surface or in the air immediately adjacent to it.

This type of diverse coating is present on virtually all indoor surfaces, and the particles, chemicals, and microbes that comprise it are in a sense, each a dynamic ecosystem. While the window glass itself may remain largely unchanged by the processes on its surface, many other surfaces are not as stable. Flooring materials or floor coverings become worn over time, and this wear depends on their material composition, the use that is made of them as well as the maintenance they are given. The wear may result in release of chemicals and particles into the air, and some of these may end up on other surfaces such as the window.

While most of these processes may occur rather slowly, there are some processes that occur much more rapidly, especially those associated with human activities or ventilation with air from outdoors. Chemical interactions produce new chemicals, and moisture on many surfaces support the life, reproduction and evolution of microorganisms. The microorganisms themselves produce chemicals, some of which can alter the pH of the surface and subsequent surface chemistry.


Building ecology was first described by research architect Hal Levin in an article in the April 1981 issue of Progressive Architecture magazine. A full discussion of building ecology and extensive resources can be found at the Building Ecology website, buildingecology.com.