New Zealand has long been perceived by the outside world as having a “clean, green” image, but there is more to sustainability than merely being green. Sustainability has many definitions, but all relate to “treading lightly”, “leaving only footprints” and “ensuring we leave our planet in a fit and proper state for future generations”.
A popular view of sustainability links it to being environmentally sound, but there are elements of economic viability, together with social issues, that must be considered. Build magazine recently contained an article by Professor Raymond Cole of the School of Architecture, University of British Colombia, Canada.
He produced the table at right which shows the major shift needed to move from “Green” to “Sustainable”. The impact of the social and economic issues can clearly be seen. Sustainability is a long-term issue.
Outlined recently in a British concrete publication was research that illustrates how, over the life of a home, the whole-life operational carbon dioxide emissions of a house have far more environmental impact than the embodied carbon dioxide of the materials used to build it.
The research compared lightweight timber homes with medium-weight and heavyweight masonry and concrete homes, and found that those in the heavyweight group can have the lowest total energy consumption and carbon dioxide emissions over their life cycle.
The New Zealand Government is placing increasing importance on sustainability. In all government purchases, whether it be a box of tissues or a multistorey building, sustainability must be considered.
Nowhere can this impact be seen more clearly than in the Department of Building and Housing’s review of the Building Code. In the Minister’s own words: “This review provides the opportunity to take a fundamental look at how we design and build, and how our built environment works for us as people and communities.
It will enable technical, environmental and societal needs to be considered together. “This will involve considering a broad range of issues such as what does sustainability and energy efficiency mean in the context of buildings and houses, the impacts of our changing population on the type of buildings we need, and how to balance short-term cost with long-term benefits.”
With such emphasis on sustainability in the new code, the Cement & Concrete Association NZ has commissioned BRANZ to draw together available information from around the world to place the contribution concrete makes to sustainable development in New Zealand in context.
Among inherent properties of concrete which contribute to a sustainable built environment are: Durability: Concrete has extraordinary durability. It will not rot, rust or corrode. Concrete’s high resistance to wear and damage, including its ability to withstand earthquakes, tsunamis and extreme weather conditions means minimal maintenance over a prolonged whole of life.
solar design, concrete is crucial to the moderation of internal temperatures, particularly if the concrete used is a component of the building’s structure.
At the core of passive solar design is concrete’s thermal mass — the ability to absorb and store heat throughout the day, and release it during the night, creating a thermally efficient and comfortable living environment all year round.
Concrete has benefits over lightweight construction in some aspects of acoustic management, specifically reducing airborne noise transmission, reducing noise from the external environment and providing sound separation between adjacent rooms.
Fire Resistance: Concrete is non-combustible, non- flammable and more robust in fire than other structural systems as it can absorb a greater amount of heat before reaching critical overload.
It is important that the differences between simply being green and shifting the paradigm to supporting sustainable patterns of living are well understood, and the associated social and economic issues such as longterm thinking and life-cycle assessment are embraced.