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Long-spans amplify the collaborative relationship between architects and engineers

By: Richard C. Master, AIA, CSI
Chair Emeritus, Specifications and Building Technology, Professional Interest Area (PIA), AIA
Manager, Architectural Systems
USG Corporation

	Gypsum board scores extremely high on nearly all sustainable design criteria. It is made from an abundant and non-endangered mineral (gypsum) and has low embodied energy. Drywall made from recaptured gypsum reduces landfill waste resulting from fossil-fuel power plant generators.
	Environmentally friendly gypsum fiber panel floor underlayments (shown here) and exterior sheathings are made from 95 percent recycled materials, offering a sustainable alternative to wood-based products such as lauan.
	Most acoustical ceiling panels consist of approximately 40 percent mineral wool, which is usually made from slag, a by-product of steel manufacturing. The use of slag eliminates the need to mine and process naturally occurring materials, while reducing landfill waste.

The virtues of the reduce, recycle and renew principles must be balanced with an awareness of how embodied energy impacts sustainability. Embodied (or embedded) energy is the amount of non-renewable energy required to extract, manufacture, transport and construct building products. It must be factored into all green product specifications, as it can have a significant – and sometimes surprising – impact on sustainable design.

Generally speaking, products with low embodied energy are good sustainable design choices. However, this is not to say that products with high embodied energy are always poor sustainable choices. A high embodied energy product containing large amounts of thermal mass may provide significant savings in energy usage over the life cycle of a building. The initial high embodied energy in the product is more than compensated for by its ability to reduce a building’s recurring long-term energy needs (e.g. heating and cooling).

One aspect of embodied energy that is sometimes overlooked is material transportation. Transportation requires the use of non-renewable fossil fuels, which under certain circumstances can negate the benefits of an otherwise excellent sustainable product selection.

Consider the use of gypsum board. In certain areas of the country, the product is manufactured using recaptured gypsum formed as a by-product of operations in some power plants. The coal burned in many of these facilities produces undesirable pollutants, including sulfur dioxide. Wet limestone scrubbers are often used to prevent this pollution from entering the atmosphere. As the exhaust smoke from the power plant rises through the scrubber, its pollutants are chemically removed. The calcium and water in the wet limestone combine with the sulfur dioxide to create calcium sulfate, or recaptured gypsum. Gypsum manufacturers source this recaptured gypsum to produce wallboard, thereby reducing landfill waste. The wallboard made from recaptured gypsum is indistinguishable in terms of performance and quality from panels made from mined gypsum rock.