Impact of product lifetime on life cycle assessment results

Global material consumption and related environmental impacts have exceeded the carrying capacity of many ecosystems by the end of the 20th century. The construction industry, being one of the most important industries for most nations, is responsible for a notable portion of materials consumption and environmental impacts.;Life cycle assessment (LCA) can be used to quantify environmental impacts of products and processes. However, many life cycle assessment studies do not adequately address the actual lifetime of buildings and building products. The goal of this research is to improve the LCA method and its results by quantifying the impact of lifetime on residential buildings and building products. Including accurate lifetime data into LCA allows a better understanding of a product's environmental impact and ultimately enhances the accuracy of LCA results.;Problems associated with lifetime are identified during a life cycle study for a natural fiber reinforced composite. The issue of lifetime was then investigated at a broader level in residential buildings and building products. The U.S. residential building lifetime as well as lifetime of commonly applied interior finishes has been refined to improve the accuracy of LCA results. Existing data on lifetime and product emissions were synthesized to form statistical distributions that were used instead of deterministic values. Results indicate that average residential building lifetime in the U.S. is currently 61 years and has a linearly increasing trend. Interior finishes on average constitute 3.9% and 7.6% of life cycle energy consumption for regular and low-energy homes, respectively. As use phase efficiency of residential buildings improve, the relative importance of interior renovation over the life cycle of a residential building will increase.;Methods to estimate service life of building products have been investigated. A systematic, hybrid method for service life prediction that combines the effects of technical and social factors in a statistical approach was proposed. Example service life estimates were demonstrated for common residential interior finishes that are replaced frequently (i.e. at an interval less than the anticipated building life), and therefore require more maintenance planning and potentially have significant environmental impacts. The resulting lifetime estimation distributions have been presented for interior finishes.;Recommendations are made regarding strategies to reduce environmental impacts of interior finishes through reducing the disparity between design and actual lifetime. Existing environmental design strategies and policies have been reviewed, and specific suggestions for interior finishes are proposed. More specifically, the case for product differentiation by regionalization or by addressing the needs of different building types, and redesigning flooring overlays for disassembly and reuse was presented qualitatively.