All levels of government – and many non-government organizations – have identified sustainability as a key policy issue.

Sustainability (or sustainable development) was formally defined by the World Commission on Environment and Development (the Brundtland Commission) in 1987 in a report called Our Common Future as development that “meets the needs of the present without compromising the ability of future generations to meet their own needs.”

The concept of sustainable development recognizes that while development is necessary, it must be based upon the efficient and responsible use of limited natural, cultural, and economic resources. Sustainable development provides a framework that integrates development with environmental policies.

Those of us who work, volunteer, or are interested in heritage are aware that the conservation of existing and heritage buildings share many of the same outcomes identified as sustainability goals. However, most existing buildings – and, in particular, heritage ones – do not compare favorably with the energy efficiency of new ‘green’ buildings. This is due to the fact that most environmental assessment models utilize the easy-to-measure operational energy usage of a building instead the difficult-to-measure embodied energy of a building when calculating environmental impact.

Embodied energy is a quantitative measure of the energy consumed during the extraction, manufacture, and transportation of materials, as well as the final creation of the building. As a result, the embodied energy of a building can also be used to calculate the environmental impact of the building, and can, in particular, be used to calculate the total carbon dioxide emissions from constructing the building.

From an environmental standpoint, the embodied energy of existing buildings is one of the most compelling arguments for preserving them. When a building is demolished, energy expenditure is required and all the embodied energy is lost. Added to the environmental cost is the increase in landfill waste. Consequently,  considering the loss of embodied energy and the environmental impact resulting  from demolition is key to determining the environmental cost of a new ‘green’ building.

Heritage buildings may also be considered more durable – and consequently more sustainable – than other categories of existing buildings. First, most have necessarily and by definition lasted longer than other buildings. Heritage buildings were often constructed using the best materials and craftsmanship, which is not necessarily the case with others built more recently. And finally, heritage buildings, unlike many new buildings, are based on the principle of maintainable building assemblies. That is, individual components of an assembly can be replaced without replacing the whole assembly, minimizing operational energy costs.

Minimizing car usage and the resultant pollutants has been identified as one of the foremost goals of sustainable development. Heritage buildings and neighborhoods are, by their very nature, in accordance with this goal. Since heritage buildings are often situated in central locations in communities, the use of cars is not as necessary as in suburban developments. Heritage neighborhoods are usually in close proximity to bus, bicycle and walking routes.

Furthermore, though heritage buildings may have high operational energy costs, they often incorporate ‘green’ building concepts in their original design. For example, the use of awnings, shutters and natural ventilation help conserve energy use.

Preservation of heritage buildings also preserves the natural landscape by reducing development on new sites. This, in turn, reduces the negative environmental impact associated with developing new land.

The concept of repairing versus replacing, inherent in heritage conservation, is also inherent in sustainable development. The preservation of heritage buildings can support specialized industries such as tourism, thereby supporting societal sustainable development. In addition, heritage conservation contributes to sustainable economic development through training and employment of local specialized trades, manufacturers and industries. Finally, preserving heritage buildings preserves another limited resource: cultural objects.

The rehabilitation of existing and heritage buildings therefore shares many of the same results as sustainable, ‘green’ development. However, as we have seen, measuring the embodied energy and the durability of buildings is difficult, and there is no existing model which fully accounts for and calculates these factors. As a result, heritage buildings are not yet properly recognized for their contribution to sustainable development.

BY DIAN ROSS, CO-OP STUDENT EMPLOYEE WITH HERITAGE BRANCH

FROM HBC QUARTERLY SPRING 2007