The construction industry is a major consumer of natural resources. When the manufacturing impacts of construction materials are added on to operational impacts, buildings are significant polluters, accounting for more than 40 per cent of global greenhouse gas emissions.

The current building boom in emerging economies is creating unprecedented demand for construction materials. In India, for example, the volume of new construction doubled from 2000 to 2005, while 50 per cent of all new construction globally is occurring in China. It is expected that demand for building materials will grow by a factor of 2.5 between 2010 and 2050.

While such demand will put a strain on material availability, the environmental impacts of the manufacture of construction products are also significant. Materials such as glass, metals, bricks and cement are very energy intensive to produce. According to the Ecosmart Foundation, cement manufacturing accounts for approximately seven to eight per cent of carbon dioxide emissions globally, and approximately 1.8 per cent of carbon dioxide emissions in Canada.

Yet buildings have tremendous potential to be a force for good and can be game changers in the fight against climate change, offering the greatest potential for achieving significant greenhouse gas emission reductions at least cost. The United Nations’ Sustainable Building and Climate Initiative puts the cost per tonne of measurable greenhouse gas emission reductions in buildings below agriculture, transportation, manufacturing and energy supply.

The City of Vancouver has set a goal for all new buildings to be carbon neutral in operations by 2020. The city, along with Forestry Innovation Investment Ltd. and the University of British Columbia, retained Intep, a company with experience developing policy tools and standards for very low carbon buildings, and Vancouver-based Brantwood Consulting to develop a methodology that may be used to inform the operating and embodied energy and carbon footprint of a wide range of building types. Intep and Brantwood then created a framework and suite of metrics for multi-unit residential buildings in B.C.’s southern coastal climate zone for Vancouver to meet the intent of its 2020 carbon neutral goal. Multi-unit residential buildings represent an important and growing building typology in B.C.

Although the embodied impacts of buildings are not yet a priority in Canada, they become increasingly important as buildings become more operationally efficient. The findings from the Intep/Brantwood work suggest that the embodied emissions estimated at approximately 7 kg CO2 eq./(m2 yr) in a typical multi-unit residential building constructed to current standards in southwest B.C. are about a quarter of the operating emissions (about 28 kg CO2 eq./(m2 yr), assuming a 60-year life of the building. However, when the same building is designed to achieve an operational carbon dioxide emissions target of 5 kg CO2 eq./(m2 yr), which meets the intent of Vancouver’s 2020 carbon neutral goal, the average embodied emissions of 7.5 kg CO2 eq./(m2 yr) now exceed the operational emissions.

The study looked at both concrete and wood frame buildings, which can be built up to six-storeys in B.C.

Recognizing that most climate action targets are projected out to a “post-carbon” economy in 2050, the Intep/Brantwood study proposed a 2050 operating emissions target of 2.5 kg CO2 eq./(m2 yr). Unless regulatory controls are in place, average embodied carbon emissions may climb to 8 kg CO2 eq./(m2 yr), assuming current technologies.

By setting total combined operating and embodied energy and carbon emission limits, designers can choose an optimal suite of measures for their projects while providing a more complete account of a project’s environmental impacts. For example, the operational performance benefits provided by the thermal mass of a heavy building may be traded off against the more intensive embodied impacts. Alternatively, low carbon materials such as wood may afford a designer more choice when it comes to type of building systems. Importantly, such decisions are made objectively and based on science. However, material choice clearly matters.

Embodied energy and carbon considerations are not yet part of any building policy in North America. The Intep/Brantwood study shows these impacts need to be brought into the regulatory environment soon. As international interests in common environmental metrics align in response to the global challenge of climate change, it is logical to establish consistent, long-term, science-based and globally equitable carbon emission performance targets for embodied and operational impacts. It is also important to provide designers a flexible policy environment within which they can make informed science-based decisions about materials in a way so that their efforts in bringing down carbon emissions are not compromised.

Helen Goodland is managing partner of Brantwood Consulting, a Vancouver-based consultancy that provides sustainability advisory services to the real estate industry. Stephan Tanner is a principal with Intep USA, which offers high-performance architecture, engineering and real estate consulting.