Wood Wins with LCA

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The chart below illustrates how each of the designs performed against five key indicators of environmental impact. With two exceptions, the wood-framed homes performed substantially better than their non-wood counterparts. The steel design produced slightly less solid waste and there was no significant difference in emissions to water in Atlanta.

MINNEAPOLIS DESIGN	Wood	Steel	Difference	(% Change)
Embodied Energy (GJ)	651	764	113	17%
Global Warming Potential (CO₂ kg)	37,047	46,826	9,779	26%
Air Emission Index (index scale)	8,566	9,729	1,163	14%
Water Emission Index (index scale)	17	70	53	312%
Solid Waste (total kg)	13,766	13,641	-125	-0.9%

ATLANTA DESIGN	Wood	Concrete	Difference	(% Change)
Embodied Energy (GJ)	398	461	63	16%
Global Warming Potential (CO₂ kg)	21,367	28,004	6,637	31%
Air Emission Index (index scale)	4,893	6,006	1,114	23%
Water Emission Index (index scale)	7	7	0	0%
Solid Waste (total kg)	7,442	11,269	3,827	51%

Another study conducted by the Canadian Wood Council compared the life cycle impacts of three 2,400 square foot homes designed primarily in wood, steel and concrete over the first 20 years of their lives. Relative to wood, the steel and concrete homes were predicted to:

Release 24 percent and 47 percent more air pollution
Produce 8 percent and 23 percent more solid waste
Use 11 percent and 81 percent more resources
Require 26 percent and 57 percent more energy (from extraction through maintenance)
Emit 34 percent and 81 percent more greenhouse gases
Discharge 4 and 3.5 times more water pollution

These differences may seem small until one realizes that only a small portion of the materials in a house (by weight) are involved in framing. One can expect the impacts to be many times greater when components made from different materials are compared directly.

Sources

The Environmental Performance of Renewable Building Materials in the Context of Residential Construction – Consortium for Research on Renewable Industrial Materials (CORRIM), 15 pages ( 128KB PDF)
Energy and the Environment – Canadian Wood Council, 16 pages ( 426KB PDF)

More information

The Athena Institute – Offers the ATHENA® EcoCalculator for Assemblies, which provides free LCA results for more than 400 common building assemblies as well as its parent tool, the ATHENA® Impact Estimator for Buildings
- EcoCalculator Fact Sheet ( 118KB PDF)
- Impact Estimator Fact Sheet ( 118KB PDF)
- Life Cycle Assessment Tools Fact Sheet ( 164KB PDF)
National Institute for Standards and Technology – Product-focused, offers the BEES® LCA software (Building for Environmental and Economic Sustainability)
Life Cycle of Wood Products – Canadian Wood Council, 1 page ( 227KB PDF)
Wood and Green Building: The Role of Life Cycle Assessment – Wood Promotion Network, 2 pages ( 901KB PDF)

The ATHENA® Impact Estimator for Buildings is capable of modeling 95% of the building stock in North America, including industrial, institutional, office and residential designs, and simulating over 1,000 assembly combinations. The ATHENA® EcoCalculator for Assemblies provides instant LCA results—free of charge—for more than 400 common assemblies based on detailed assessments conducted using the Estimator.

Click here to use the EcoCalculator.