In major cities, like Toronto, thousands of buildings line the street, each built with tonnes of material, and with a total of 157 skyscrapers proposed, built or in progress, Toronto is on track to be only behind New York in number of skyscrapers, across North American cities. It is easy to focus on the sounds of construction when it wakes you up in the morning, but more thought-provoking discourse arises when discussing building materials, brought to light through life cycle analysis.
Building a Building
Of many important factors in building materials, seven logistical ones stand out: aesthetic, structural, thermal control, moisture control, air leakage control, cost and safety. An obvious critical factor is cost. While cost between materials can be small in magnitude, extending costs to skyscrapers can make a dollar per square footage an incredible and determining factor.
Aesthetics are not only important to the average consumer for pride in their home, but can also be extended to real estate and investment strategy. The material selection follows the aesthetic design principles in architecture, such as texture, symmetry, contract and colour balance. In addition to appearance, though important for buyers and sellers, material needs to be strong and durable to ensure safety, as well as easy to fabricate.
Structural and logistical aspects are critical, and can be conflicting. Another selection criteria is heat insulation, which conflicts with structural capacity, as the need for low density (as to maintain low thermal conductivity) reduces the structural capacity of most insulation, such as concrete. Similarly, air and moisture control measures are critical in choosing materials; the introduction of moisture and air can lead to mold and material degradation, while holes that allow for air leakage may lead to increased heating and cooling costs and pollutants, an important aspect in downtown Toronto. Beyond this, decreased heating and cooling demands also lowers the amount of greenhouse gases needed and produced.
Above all, the health and safety of inhabitants is of the utmost importance. Ageing buildings, with asbestos and other harmful chemicals, have brought to the forefront the importance of designing for safety and the future in choosing building materials, and in designing building materials.
Making Choices: Sustainability-driven Design
In recent years, a focus on sustainability has risen in building circles. With building materials’ contributions comprising 11% of global emissions of greenhouse gases, any shift can make a difference in climate change. Various companies have gotten creative, like CarbonCure Technologies, a Canadian company that uses industrially produced carbon dioxide in their concrete mixture, which then mineralizes, thereby reducing carbon dioxide emissions. The University of Toronto has announced plans to build a timber building, therefore avoiding materials that require creating a large amount of carbon emissions in production.
It is this shift in focus toward sustainability that has drawn attention to life cycle assessments (LCA) in various sustainability accreditations, like the LEED rating system, when choosing various building materials. Life cycle assessments allow for designers to fully understand environmental impacts along the life of materials, from material recovery to disposal, and other waste produced, like greenhouse gases.
Life cycle assessments and a focus on sustainability has drawn other forms of creative sustainable solutions, other than designing new materials, like retrofitting existing buildings and salvaging materials. For example, Mountain Equipment Co-op (MEC), salvaged timber from the bottom of rivers for their Ottawa store, and repurposed steel beams. Another trend is deconstruction, a retrieval of reusable structural components (eg. bricks) from existing buildings, to avoid the whole stream going toward landfills, while possibly bringing down the costs compared to buying newly produced materials.
As an important tool in discovering environmental impacts, life cycle assessments are critical in shaping buildings of the future, and the materials that make them. The current discourse of environmental sustainability with respect to global construction calls for creative action and holistic design with the future in mind.