Building assets

Traditional building materials (McMartin House, Perth)

Photo: Traditional building materials (McMartin House, Perth)

Contemporary building materials (Seagrams)

Photo: Contemporary building materials (Seagrams)


Romas Bubelis

Buildings and architecture, Environment

Published Date: Nov 15, 2007

Which is more sustainable – an artificial or live Christmas tree? This is an environmentalist’s conundrum, and it illustrates the paradox of “sustainable” building materials.

Use of natural building materials diminishes a tangible resource. But the production of substitute, synthetic building materials consumes an even wider range of energy resources. At one end of the spectrum are materials such as wood. Lumber is a renewable resource. Akin to this are materials such as locally quarried stone and brick that require only modest energy to produce.

It is no coincidence that these are the low energy-intensive materials of traditional construction. But their use in contemporary architecture is in decline while the use of high energy-intensive materials – such as vinyl, glass and aluminum – is on the rise.

There is a tremendous amount of energy expended to produce new, technologically innovative building materials. Most are composite materials, often transported over long distances between source of material extraction, location of manufacturing and location of use. One unit of brick takes about twice the energy to produce as does the equivalent unit of local natural stone. A given unit of glass requires six times the energy of an equivalent volume of brick. The manufacture of aluminum requires a supply of bauxite ore, a smelting plant and huge amounts of electricity. As a result, producing one unit of aluminum consumes 900 times the energy needed to produce the equivalent amount of lumber.

In the sustainability era, every material is said to have an “embodied energy.” This concept is used to measure the true “energy value” of a building material or assembly over the course of its service life.

It is the sum total energy necessary to create and sustain an assembly and it takes into consideration a full life cycle of energy-consuming activities: raw material extraction, transportation, manufacturing, assembly and construction, collectively referred to as “initial embodied energy;” cyclical maintenance, restoration, and repair referred to as “recurring embodied energy;” and, finally, the energy expended to disassemble, demolish and recycle or dispose of building materials that are no longer needed. The embodied energy concept is as complex as it is holistic – it considers the energy used to create a material, but also the accumulated energy that is lost when, years later, that material is taken to landfill.

Maintenance and restoration activities add embodied energy value without consuming additional natural resources. It prolongs the service life of buildings and reduces landfill as well as the consumption of resources to produce replacement material. The most sustainable material is the one that required little energy to produce and, through maintenance and care, has provided decades of service. In architectural heritage conservation, as in environmental sustainability, it is far better to maintain and repair than to replace. The greenest building is the one you already have.