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Material Ecologies

Throughout their life cycle, from conception to disassembly, buildings affect natural and cultural ecologies at regional and global scales. Life Cycle Assessment (LCA) methods can measure these material and energy flows inherent to the building. Long-lived buildings reduce the share of embodied resources and environmental impacts borne by each generation that inhabits them: making durability an imperative for sustainability.

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Material Ecologies maps the flows and life cycle impacts of four common structural materials: concrete, steel, masonry, and timber. Four contemporary architectural precedents represent each material as a primary structural system—usually the most durable component of a building—showing their benefits, tradeoffs, technical innovation, and unique architectural expression. By revealing and comparing these otherwise invisible material ecologies, we can understand the complex factors facing architects when designing for sustainability.

Photo: Michelle Laboy

Constructing a building on a specific site also creates a globe-spanning web of physical relationships based on the resource extraction, refinement, transportation, and assembly of materials. Even simple building materials may contain many constituent elements and require many steps and processes. This map illustrates one of the many life cycle impacts of a building: its journey through the modern global economy. While not exhaustive in the materials or processes, the complexity of the map reveals economic, social, and resource disparities across the world generated by four built examples. The flows may suggest materials move freely across territorial boundaries, but the traces of economic agreements, and even colonial history remain.


This map was drawn with the Waterman Butterfly projection, which minimizes distortion, preserving equal surface areas while shifting our perception of the relationships between continents. Architect Bernard Cahill first developed the concept of unfolding the globe as eight equal segments of a sphere in 1909. In 1996, physicist and mathematician Steve Waterman updated a version of Cahill’s map based on his geometric research.

Photo: Mic L. Angelo


How We Measure Matters

Photo: Mic L. Angelo

How We Measure—Gross Versus Net

How We Measure—Per Person

Embodied Carbon: How We Measure Matters

Among other environmental consequences, making materials and assembling them contributes to global warming. For simplicity, we sum up those contributions as if they all came from carbon dioxide, use units of carbon dioxide equivalent (CO₂eq) to measure and use carbon as a shorthand for global warming potential. Although the greenhouse gases are emitted into the atmosphere, their environmental impact is embodied, or built into in the material, thus embodied carbon.

To measure the environmental impact of material choices rather than the occupants or operations, this wall of the exhibition tallies each building’s emissions from cradle to gate, including everything from raw resource extraction to a finished but unoccupied building. Unlike the wall behind and to your right, these tallies do not consider building lifespan, or what happens to the materials when the building reaches end of life.

The four buildings in this exhibition are different sizes. To compare them, the total embodied carbon of each is normalized, or divided by units of floor area. The way we measure and compare buildings profoundly shapes our thinking about embodied carbon and its relationship to decisions about building compactness, spatial efficiency, urban form, and density. These graphs illustrate different ways to measure embodied carbon, providing different perspectives on performance.

Structural Area

This composite object compares the sizes of columns made of steel, concrete, timber, and brick that support the same weight.

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The steel on top is equivalent to the columns at the Salt Lake City Courthouse by Thomas Phifer and Partners. These columns have extra capacity to support more weight if a nearby column fails, and the greatest structural efficiency—the ratio of weight supported to the weight of the structure. Adding necessary fire protection increases these columns small footprint.

Timber is the second most efficient because the glulam is made of narrow pieces of Douglas Fir selected to better resist axial forces parallel to grain. The large combined mass is more fire resistant than the individual pieces of wood.

Concrete has only a slightly larger cross-sectional area than timber, thanks in part to the strength of the steel reinforcement, which is protected from fire by the concrete.

A masonry pier built with the Porotherm brick requires the largest cross-sectional area, in part because it is designed with many voids to increase insulation.

Spatial efficiency is more important in dense urban areas where land is limited and compactness is desirable, one of many tradeoffs of higher embodied carbon structures. Lower-carbon, high-efficiency structures may be in the horizon with engineered timber.

Photo: Michelle Laboy

Wedding Cake

Curator Michelle Laboy explains the object referred to as the "Wedding Cake", which shows four columns stacked on top of each other. Each column is made of one of the four different materials to illustrate how much of each material it takes to support the same weight load.

Material Timeline: Environmental Impacts of Varying Building Lifespan

Material choices in architecture are measured in and over time as well as space; not only do durable buildings replace fewer components, they divide their environmental impact over a longer time.

These graphs measure the global warming potential from each example building’s construction, repair, maintenance and replacement, as well as demolition and the subsequent reuse or recycling of materials. In addition to the four examples, it includes a data for a typical contemporary building with a short life and frequent replacement. The stacked bars on the left show a baseline, as if the building were demolished as soon as it was constructed. The lines extending to the right illustrate the accumulating environmental impact of each building depending on how long they last.

Like the rest of this exhibition, these data do not include the carbon from the operating energy used for heating, cooling, lighting, and equipment. Unlike the data in “How we Measure Matters” this wall includes the end of a building’s life, so metals may be recycled, while wood releases carbon by decomposing or burning.

Timeline Revised

Photo: Mic L. Angelo

Looking to explore Material Ecologies at home? Download the worksheet, seen below, to build your own Octahedral Globe and Carbon Cube HERE.

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