by Nils V. Ericson, PE

Sustainable design is an approach to building design that recognizes the limitations of our natural resources and our obligation to future generations to lessen our impact on the environment. It adds a dimension to all our decisions in the design process to evaluate the environmental impact of our choices. We must consider the consequences of our design - how our building performs and how it affects the environment.

Sustainable design is aimed at reducing the environmental and health impacts caused by the construction and operation of buildings. It focuses on energy efficiency, indoor environmental quality, material selection, site planning, resource efficiency, and water use in order to reduce the associated negative impacts

Materials used in the building industry make an enormous impact on the environment due to the acquisition of materials and resources, energy used, and waste generated during the production, use and disposal of building materials. Many materials off-gas, emitting hazardous substances into the air during installation and sometime long after buildings are occupied. Materials can add long-term cost due to replacement and maintenance if not properly selected. In the past, it has been assumed that materials should be new and from virgin sources, placing an unnecessary burden on the environment due to the extraction of resources for material production.

Structural Building Systems Perhaps not as dramatic as the energy efficiencies that are achieved through decreased heating, cooling and lighting demands, structural systems can play an important role in sustainable solutions. Choice of structural systems, materials and member arrangement can provide a pleasant appearance without the need for finish materials. A high-tech and interesting space is achieved with exposed structure while the cost of producing and purchasing ceiling tiles, wall materials and floor finishes can be minimized.

Exposed and painted metal decks and steel structure can serve as a ceiling where fire-rating requirements permit. Where fireproof structure is necessary, concrete frames and floor systems provide that along with smooth finishes when high quality formwork is specified. The coffered underside of two-way waffle slabs and ribbed surfaces of concrete joist systems also provide interesting ceilings, either painted, or not. Staining the concrete floor slabs results in unique floors and saves the floor covering and adhesive materials that expend natural resources, require energy for production and eventually add to waste.

Further opportunities for sustainable solutions with the structural systems:

• Recycled Steel. Structural steel is a recycled product being produced from scrap steel products.
• Fly ash use in concrete. Fly ash, produced from the combustion of coal, usually in electrical power plants, is a potentially hazardous waste material that can be used to replace up to 25% of the portland cement binder in concrete.
• Certified Forest Products Council. Wood structural materials from a forest source certified as sustainably well managed.
• Responsible Structural Engineering. Effective application of structural analysis and design principles results in an efficient structural system that will safely resist the natural forces and occupant loads with minimal use of structural materials.