Get a life (cycle)

Green building rating systems, such as U.S. Green Building Council's LEED, Green Globes, and BREEAM, encourage designers to select products and materials that minimize the negative environmental impacts of building products over the lifetime of a building. Such considerations are embodied in what is known as a lifecycle analysis (LCA).

08/01/2008


Green building rating systems, such as U.S. Green Building Council's LEED, Green Globes, and BREEAM, encourage designers to select products and materials that minimize the negative environmental impacts of building products over the lifetime of a building. Such considerations are embodied in what is known as a lifecycle analysis (LCA). Although current rating systems give a nod to LCAs, they do not specify how to perform one.

Engineers are knowledgeable on first costs, energy costs, and lifecycle costs. LCAs complement economic accounting with environmental accounting by determining overall energy use and environmental impact from cradle to grave. This means starting the analysis with the production of every component that goes into the building, and ending when every component is recycled, reused, or trashed. Think of LCA as lifecycle costing, but replace capital and operating expenses with energy use and environmental impacts such as greenhouse gas (GHG) emissions. You also should include energy consumption and associated GHG emissions for extracting and shipping virgin materials, assembling and shipping components and final products, and installing and maintaining the products in the building.

You also may ask if LCA is just another trendy method that will slow down an already-difficult design and construction process. Or will it encourage (and even pay) engineers, architects, and project financiers to think about the big picture when making decisions on building projects? When would this complicated process be used, and what are some predicted results based on commonly used building components?

The answers to these questions largely depend on the availability of data and software to perform LCAs. Some resources are now available, such as version 4.0 of Building for Environmental and Economic Sustainability (BEES), developed by the National Institute of Standards and Technology (NIST). According to NIST, BEES measures the environmental performance of building products by using the LCA approach specified in the ISO 14040 series of standards. See www.bfrl.nist.gov/oae/software/bees for more information.

You also may ask if MEP systems are significant compared to other building components, such as the envelope and furnishings. The answer is yes. A doctoral dissertation, published in 2004 by Seppo Junnila at the Helsinki University of Technology Construction Economics and Management, reports that HVAC and electrical systems cause 60% to 75% of a commercial office building's lifecycle impact.

While Junnila's data may not be applicable to every building type, it is evident that, from cradle to grave, MEP systems can account for the vast majority of energy and environmental impacts in all building systems. This is because materials commonly used in mechanical and electrical systems, such as steel, copper, and rubber, have some of the highest embodied energy values per unit weight compared to materials such as brick, concrete, and glass. Examples of this data were published for different building materials in “Inventory of Carbon and Energy (ICE)” by Geoff Hammon and Craig Jones, with the Dept. of Mechanical Engineering at the University of Bath, U.K. The data are very comprehensive, but there is no straightforward method to apply them to real-world projects.

While these types of studies still are not very common, and comprehensive data sets and application tools are not readily available, MEP designers should become familiar with and start using LCA to complement other analysis and decision-making tools they are using.


Author Information
Kosik is the leader of “Moving Towards Sustainability,” one of eight corporate pillars at EYP MCF, which focuses on the research, development, and implementation of sustainable design strategies for high-performance buildings. He also is a member of CSE 's Editorial Advisory Board.




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