Tag Archives: ecology

Understanding the Living Building Challenge and Its “Petals”

The Living Building Challenge (LBC) is a certification program that defines the most advanced measure of sustainability—providing a framework for design, construction and the symbiotic relationship between people and all aspects of the built environment. It is one of most rigorous performance standards in the industry, as it requires net-zero energy, waste and water by every project. Continue reading


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.

Buildings constantly evolve as a result of the changes in the environment around them as well as the occupants, materials, and activities within them. The various surfaces and the air inside a building are constantly interacting, and this interaction results in changes in each. For example, we may see a window as changing slightly over time as it becomes dirty, then is cleaned, accumulates dirt again, is cleaned again, and so on through its life. In fact, the “dirt” we see may be evolving as a result of the interactions among the moisture, chemicals, and biological materials found there.

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.

Buildings are designed or intended to respond actively to some of these changes in and around them with heating, cooling, ventilating, air cleaning or illuminating systems. We clean, sanitize, and maintain surfaces to enhance their appearance, performance, or longevity.  In other cases, such changes subtly or even dramatically alter buildings in ways that may be important to their own integrity or their impact on building occupants through the evolution of the physical, chemical, and biological processes that define them at any time. We may find it useful to combine the tools of the physical sciences with those of the biological sciences and, especially, some of the approaches used by scientists studying ecosystems, in order to gain an enhanced understanding of the environments in which we spend the majority of our time, our buildings.

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.

Buildings and Light Pollution

trees-plants-noise-pollution-120320-676015-Ecological light pollution is the effect of artificial light on individual organisms and on the structure of ecosystems as a whole.

When animals live in cities, they have to adjust their behavior and life histories to novel environments. Noise pollution puts a severe constraint on vocal communication by interfering with the detection of acoustic signals. Recent studies show that city birds sing higher-frequency songs than their counterparts in non-urban habitats. This has been interpreted as an adaptation to counteract masking by traffic noise.

Similarly, anthropogenic light and noise have modified differences between day and night, and may thereby interfere with their circadian clocks. Urbanized birds as well as many other species are known to advance their activity into early morning and night hours. Studies indicate that city birds start their activity earlier and had faster but less robust circadian oscillation of locomotor activity than their forest relatives. Circadian period length predicted start of activity in the field, and this relationship was mainly explained by fast-paced and early-rising city birds.

 In the article “Ecological Light Pollution” from the publication Frontiers in Ecology and the Environment by the Ecological Society of America it is reported that “through the various effects that light pollution has on individual species, the ecology of regions is affected. In the case where two species occupy an identical niche, the population frequency of each species may be changed by the introduction of artificial light if they are not equally affected by light at night. Changes in these species frequencies can then have knock-on effects, as the interactions between these species and others in the ecosystem are affected and food webs are altered. These ripple effects can eventually affect even diurnal plants and animals. As an example, changes in the activity of night active insects can change the survival rates of night blooming plants, which may provide food or shelter for diurnal animals.

The introduction of artificial light at night is said to be one of the most drastic anthropogenic changes to the Earth, comparable to toxic pollution, land use change, and climate change due to greenhouse gases.

The Urban Heat Island Effect


Aerial view of the city of Los Angeles California

An urban heat island is the name given to describe the characteristic warmth of both the atmosphere and surfaces in cities (urban areas) compared to their non-urbanized surroundings. The heat island is an example of unintentional climate modification when urbanization changes the characteristics of the Earth’s surface and atmosphere.

As cities add roads, buildings, industry, and people, temperatures in the city rise relative to their rural surroundings, creating a heat island. These urban heat islands may be up to 10-15°F warmer under optimum conditions. With increasing urban development, heat islands may increase in frequency and magnitude. Los Angeles, California, for example, has been 1˚F hotter every decade for the past 60 years. These heat islands have impacts that range from local to global scales and so represent a significant impact on environmental change.

There are three types of heat islands: 1). canopy layer heat island (CLHI), 2). boundary layer heat island (BLHI), and, 3). surface heat island (SHI).

The first two refer to a warming of the urban atmosphere; the last refers to the relative warmth of urban surfaces. The urban canopy layer (UCL) is the layer of air closest to the surface in cities, extending upwards to approximately the mean building height. Above the urban canopy layer lies the urban boundary layer, which may be 1 kilometer (km) or more in thickness by day, shrinking to hundreds of meters or less at night. It is the BLHI that forms a dome of warmer air that extends downwind of the city. Wind often changes the dome to a plume shape.

Heat island types vary in their spatial form (shape), temporal (related to time) characteristics, and some of the underlying physical processes that contribute to their development. Scientists measure air temperatures for CLHI or BLHI directly using thermometers, whereas the SHI is measured by remote sensors mounted on satellites or aircraft.

A number of factors contribute to the occurrence and intensity of heat islands; these include: 1). weather, 2). geographic location, 3). time of day and season, 4). city form, and 5). city functions.

Weather, particularly wind and cloud, influences formation of heat islands. Heat island magnitudes are largest under calm and clear weather conditions. Increasing winds mix the air and reduce the heat island. Increasing clouds reduce radiative cooling at night and also reduce the heat island. Seasonal variations in weather patterns affect heat island frequency and magnitude.

Geographic location influences the climate and topography of the area as well as the characteristics of the rural surroundings of the city. Regional or local weather influences, such as local wind systems, may impact heat islands; for example, coastal cities may experience cooling of urban temperatures in the summer when sea surface temperatures are cooler than the land and winds blow onshore. Where cities are surrounded by wet rural surfaces, slower cooling by these surfaces can reduce heat island magnitudes, especially in warm humid climates.

City form comprises the materials used in construction, the surface characteristics of the city such as the building dimensions and spacing, thermal properties, and amount of greenspace.

Heat island formation is favored by: 1). relatively dense building materials that are slow to warm and cool and store a lot of energy, 2). replacement of natural surfaces by impervious or waterproofed surfaces, leading to a drier urban area, where less water is available for evaporation, which offsets heating of the air, and 3). lower surface reflectivity to solar radiation — dark surfaces such as asphalt roads absorb more sunlight and become much warmer than light-colored surfaces.

City functions govern the output of pollutants into the urban atmosphere, heat from energy usage, and the use of water in irrigation. Anthropogenic heat, or heat generated from human activities, primarily fossil fuel combustion, can be important to heat island formation. Anthropogenic heating usually has the largest impact during the winter season of cold climates in the downtown core of the city. In select cases, very densely developed cities may have significant summertime anthropogenic heating that results from high energy use for building cooling.

Your Ecological Footprint

Recycle BuildingEcological footprint is a term commonly used in sustainable building practice as a measure of our demand on earth’s resources. More specifically, it represents the amount of biologically productive land and sea area necessary to supply the resources necessary to a given population. Since resource utilization is dependent on personal lifestyle, the ecological footprint can be considered to be a quantification of the demand for natural capital needed to support a given lifestyle.

This unit of measure was first conceptualized in the PhD dissertation of Mathis Wackernagel under the supervision of William Rees at the University of British Columbia in Vancouver in 1988. Originally the two men called their concept “appropriated carrying capacity”. The revised term, “ecological footprint”, was coined in their book, “Our Ecological Footprint: Reducing Human Impact on the Earth” in 1996.

When calculated at the level of cities and countries, the measure provides a useful indicator of the relative demand on resources for any given population base. An ecological footprint calculation indicates that, for example the Dutch need a land are 15 times the physical footprint of the Netherlands to support their population. The population of London requires a land area 125 times greater than its physical footprint. William Rees’ ecological footprint analysis of his home city of Vancouver, Canada indicates that Vancouver appropriates the productive output of a land area nearly 174 times larger than the city’s physical area to support its lifestyle.

When considering the ecological footprint on the individual level, given Earth’s 8.9 billion hectares of productive land and its 6 billion human inhabitants, the average ecological footprint comes to roughly 1.5 hectares per person.  This per-capita footprint provides a benchmark from which to assess the long-term sustainability of material consumption.  Accordingly, individual footprints below 1.5 hectares are sustainable and footprints above 1.5 hectares are not. Wackernagel and Rees’ original calculations indicate that inhabitants of industrialized countries often have footprints as large as four (4) to ten (10) hectares, i.e. up to six times the carrying capacity of the planet.

What is your personal ecological footprint? A number of non-governmental agencies (NGOs) offer online ecological footprint calculators. One of them is at Footprint Calculator.

Some resources available for further reading include Wackernagel’s original thesis “Ecological Footprint and Appropriated Carrying Capacity: A Tool for Planning Toward Sustainability” and William Rees’ 1992 paper, “Ecological Footprints And Appropriated Carrying Capacity: What Urban Economics Leaves Out“.

Living Machines


The Living Machine at Lewis Center for Environmental Studies at Oberlin College

One of the ultimate goals of green building is the application ecological design to the greatest extent possible, including a synergistic relationship between natural systems, buildings, and human inhabitants.

The use of wetlands to treat wastewater effects of buildings is well known and is becoming mainstream – most of us are familiar with the use of landscaping bioswales to filter storm water effluent before discharging it back into the aquifer.

A more exotic and robust use of ecosystems to treat building effluent is the so-called Living Machine, in which nature is brought directly into a built structure in order to break down the effluent – both greywater and blackwater – as part of the wastewater treatment system. Several approaches are in use, although the best known is said to be that pioneered by John Todd, an early exponent of the development of natural wastewater processing systems.

Contrasted with conventional wastewater treatment plants, a Living Machine is different in four major ways:

  1. A Living Machine fundamentally relies on living organisms, rather than mechanical parts, to produce work. These “cogs” in the machine can include hundreds of species of bacteria, plants, invertebrates, and even vertebrates including fish and reptiles.
  2. A Living Machine regulates its own internal ecology in relationship to the energy and nutrient streams feeding it.
  3. Should it be stressed by toxic substances or by interruption of its energy or nutrient streams, the Living machine is self-healing and self-regulating.
  4. A Living Machine is capable of self-replication through the propagation of its constituent organisms.

Among the most famous examples of Living Machine is that at the Lewis Center for Environmental Studies at Oberlin College in Oberlin OH. Local, regional examples occur at San Francisco Public Utilities Commission (SFPUC) Headquarters, San Francisco and at Esalen Institute in Big Sur.

They Built Their Own Demise: Lime Mortar, Render, and Plaster: What Role in the Decline of Classical Mayan Civilization?


Chitzen Itza, west facade of the temple called “El Castillo” constructed c. 600AD. Constructed of hewn limestone blocks and whitewashed in lime plaster, the original plaster render has not survived the centuries.

A flat shelf made from the structures of ancient animals, the Yucatan was uplifted from the seabed around 10 million years ago. With its emergence from the seabed, plants arrived. Around 2500BC it is believed that the people destined to become the Maya arrived on the peninsula.

Through many generations, the Maya became the builders of cities. Each city-state of the Maya was centered at its core upon the focal buildings, the edifices signifying the status of the city, the focal point of rulership, and the city’s relationship to the gods. In the Mayan city the focal buildings generally included temples, observatories, and ballcourts. The temples served as the structures dedicated to communication with the divine, the observatories were dedicated to communication with natural cycles, and the ballcourts were associated, among other roles, with resolving internecine rivalries between city-states.

Rendering, west facade, Temple of the Descending God at Tulum depicting the painted lime plaster render typical of Mayan edifices.

Rendering, west facade, Temple of the Descending God at Tulum depicting the painted lime plaster render typical of Mayan edifices.

Each city-state had its own quarry from which the massive blocks of limestone, buildingblocks for the edifices, were hewn. More significantly, every important edifice was apparently whitewashed, as it were, with a keen layer of lime plaster and then painted in vibrant colors. Once fitted together and assembled, the building’s presentation relied on lime plaster to achieve the desired effect. The very laying up of the blocks themselves depended on lime mortar to hold them in place. Thus the architecture of the Maya depended on limestone and lime plaster for their very viability.

The conversion of limestone into either mortar or plaster relies on availability of the raw material (limestone), a ready source of fresh water, and heat. In the Yucatan the stone was readily available, and freshwater also readily available from the cenotes, the underground chambers of the Yucatan where water naturally collects. But for heat, the Maya could only rely upon the burning of forests, and the resulting deforestation is thought by many to be perhaps the ultimate reason for the collapse of Mayan civilization.


West facade, Temple of the Descending God at Tulum. Photograph by the author, July 9th, 2013.

The Maya harvested the forests around their cities to produce the heat sources necessary to the conversion of raw limestone into the mortar and plaster needed for their building projects. For plaster render, it is estimated that many square miles of deforestation were required to produce each square foot of rendered plastered surface area.

Multiply these estimates by the many thousands of building structures erected by the Maya and one can see that the baseline impacts of Mayan architecture upon the ecology could not have been slight. Add to this impacts resulting from internecine rivalries between rival city-states, and one can perceive what may have been a tipping point in the ecology of the Maya.

Competition between the Mayan city-states is well known. For example, the 60 mile causeway from Coba in the south to it’s sister-city Yaxuna in the north is understood to have been constructed for purposes of military defense of Yaxuna, ally of Coba, against the aggressions of city-state of Chitza-Itza and it’s allies.

Each Mayan city itself could be seen as the focal point for competitive interaction between rival states. As each city-state grew and naturally sought to aggrandize its own interests, other city-states sought to aggrandize theirs. Objectifying the legitimacy of the city-state required the construction of monuments, and the construction of monuments demanded resources: the quarrying of stone, harvesting of water, the deforestation of trees.

Thus, even as trees were burned to fuel the construction programs necessary to the city-state – the edifices, monuments, the roads – upon whose efforts the citizens were focused, the resources themselves were stretched beyond their carrying capacity. As the forests became overharvested, competition for the resources essential to the Mayan city-state grew commensurately, even as the carrying capacity of the land was diminished.

At the time of the invasion of the Spanish Conquistadores according to most accounts the Mayan cities were apparently by and large mostly abandoned. Tulum, on the east coast, remained among the viable Mayan cities, most others having been abandoned by the time of the arrival of the Spaniards.

Environmental degradation leading to war in turn fomenting increased competition for natural resources is not, of course, the only theory available to explain what became of the Mayan city-state – other theories abound. Having said that, the amount of environmental degradation necessary to the construction of the architecture of the Mayan city is quantifiable. What have not been quantified are the internecine and political factors which fed into their architecture, and consequent demand for resources which may have led to their demise.