To consider the current and future use of precast concrete, it is useful to look at the green building rating and assessment systems used to evaluate and reward buildings for their environmental performance. There are several systems in use in North America that promote the construction of better buildings — better for the environment, the owner and for the occupant. These systems allow many options in a project to be quantified and assessed objectively.
In North America, BREEAM Green Leaf, the web-enabled Green Globes system, and LEED are the principal rating systems used for assessing buildings where precast concrete is most likely to play an important role.
BREEAM Green Leaf is an environmental assessment protocol that was developed in response to a need for a less expensive method that could be partially conducted in-house. The method originated in Canada and was developed by ECD Energy, Environment Canada and Terra Choice. It combined a Canadian adaptation of the UK BREEAM (Building Research Establishment Environmental Assessment Method) set of environmental issues with the Green Leaf Eco-Rating procedure.
Green Globes, part of the BREEAM/Green Leaf suite of environmental assessment tools for buildings, is an online building and management audit tool that helps property owners and managers to measure the environmental performance of their buildings against best practices in areas such as energy, water, hazardous materials, waste management and indoor environment. Using a confidential questionnaire, it generates an online report.
LEED™ (Leadership in Energy and Environmental Design), developed by the United States Green Building Council (USGBC), is being adopted as a green building design and rating tool by both the architectural and engineering communities, with the LEEDTM Canada adaptation provided through the Canadian Green Building Council (CaGBC). Buildings are certified by the CaGBC based on a total point score, following an independent review and audit of selected documents submitted by a design team. With four possible levels of certification (Certified, Silver, Gold and Platinum), LEED is flexible enough to accommodate a wide range of green building strategies that best fit the constraints and goals of particular projects.
All these systems assess and reward performance with regard to design and construction management, site selection, material selection and use, operational energy use, water use, and indoor environmental quality. Within these broad categories there are specific criteria and requirements, from building reuse and waste management to new building commissioning. Precast concrete can be used in combination with a wide variety of other building materials to contribute to the achievement of a desired level of certification in any of the systems. In LEED, for example, precast concrete solutions can contribute to the achievement of up to 21 out of 70 points, leading toward a desired level of certification. The energy, material selection, construction waste management, and indoor environmental quality criteria are the most critical. Each is examined in subsequent sections.