Life-cycle green

Building green sees beyond a project's short-term bottom line to a broader payoff, delivering returns for the economy and the environment. Life-cycle costing does the long-term math so that we can maximize the life-long returns of a building.

Life-cycle costing focuses on the full costs of construction and operations, approximately 20 percent and 80 percent of a building's lifetime costs, respectively. It builds on the established practice of life-cycle assessment (LCA), which aims to quantify the environmental performance of a product or assembly from start to finish: raw materials harvesting through manufacturing, building, maintenance and operation, and finally demolition and disposal. Extensive analyses account for the impacts of energy consumption, water use, air and water emissions, toxicity, natural resource depletion, and solid waste. LCA can help evaluate building designs based on any or all of these environmental measures.

A key project advisor

By expressing environmental and health impacts in terms of economic cost, life-cycle costing puts both the first costs and operating costs of a building in perspective. It then helps minimize those impacts by informing choices of building materials and assemblies. For example, concrete fiber siding lacks vinyl siding's toxicity and is much more durable than wood. Vinyl's affordability, however, may free up funds for a more effective building envelope, enhancing durability and lowering energy use, thereby reducing overall operating costs and building impacts. Life-cycle assessment is important precisely because these decisions are so complex.

Life-cycle costing has helped develop many green building practices and products and has given rise to rules of thumb for materials use. The Materials page notes several preferable products and tips for certain categories of building components. The Waste page discusses resource-efficient design and construction approaches that fit into the "reduce, reuse, recycle" lesson of life-cycle assessment.

Governments can build capacity

To make the best use of life-cycle costing, builders must research products and assemblies, then plug that knowledge into their design process. While software tools (below) and specialty consultants are available to help, there is a considerable cost, especially for a developer's first green projects. Advice and incentives can go a long way toward helping nonprofit affordable housing developers reap the benefits of life-cycle assessment. Life-cycle assessment will also be useful for housing authority and other government building projects. To get started:

• Gather data from published assessments of product categories and ask manufacturers for information about the environmental impacts of their products; many have LCA spreadsheets.
• Use tools like ATHENA^TM to evaluate building assemblies and determine the best material mixes. Consider the foundation, floors, structural system, mechanical systems, and envelope.

Tools for life-cycle costing

ATHENA^TM Impact Estimator for Buildings lets you run life-cycle assessments of models for 95 percent of North America's building stock. With more than 1,000 different assembly combinations at your fingertips, you can put the environment on par with other design criteria. ATHENA'S databases cover new buildings and major renovations and distinguish between owner-occupied and rental facilities.

ATHENA^TM EcoCalculator for Assemblies allows you to dial up LCA results for hundreds of common building assemblies. This free software will allow you to calculate your building's climate change impacts.

BEES (Building for Environmental and Economic Sustainability) measures the environmental and economic performance of building products by using the life-cycle assessment and cost approaches specified in ISO 14040 standards and ASTM costing methodology, respectively. Released in May 2007, version 4.0 can help you compare over 230 building products.

eVALUator , from Energy Design Resources, calculates the lifecycle cost and savings of investments that improve building design. It analyzes the financial benefits, generating numbers for annual net income, repair and replacement costs, and even occupancy rates.

eQUEST , Energy Design Resources' user-friendly building energy modeling program, pairs a DOE-2 simulation with building and energy efficiency wizards and graphical reporting.

ENERGY-10^™ software, from the Sustainable Buildings Industry Council, analyzes and illustrates the energy and cost savings that can be achieved through daylighting, passive solar heating, natural ventilation, well-insulated envelopes, better windows, lighting systems, mechanical equipment, and even photovoltaic systems and solar domestic hot water systems.

Building Energy Software Tools. For many more tools, check the U.S. Department of Energy's list

Energy Star tools and resources library