A life cycle environmental and economic assessment of optimum value engineering in houses

Public concern that wood-frame construction overly stresses the forest resource has led some to advocate a reduction in the use of wood. Possible activity toward that objective includes total substitution of wood with alternative materials, a design choice already invalidated on an environmental basis by life cycle assessment (LCA). Another response has been the reinvigoration of the optimum value engineering (OVE) concept, also called advanced framing. This is a careful approach to wood design meant to reduce the volume of wood in a building, and to reduce waste. Advocates of OVE assume an environmental benefit from any wood reduction; however, OVE has never been scientifically established as environmentally preferable to conventional framing; literature on OVE has only quantified the cost savings in materials. This LCA study compared a best-practice Canadian house with one using up to 50 percent less wood, and found little or no environmental benefit; an important factor in these results was the need to incorporate non-renewable products to replace the functionality of the removed wood. Next, a house that combined some elements of efficient framing with maximum use of renewable content (e.g., cellulose insulation in place of fiberglass, wood windows in place of aluminum windows, and wood siding in place of vinyl siding) was compared to the conventional house, and showed strong environmental benefits. These data provide a good argument for maintaining, not decreasing, the renewable content in a house, provided that public confidence in sustainable forestry in North America is continually improved.