Examination of Exterior Wall Assemblies Using a Full Costs Accounting Framework and Benefit Costs Analysis.

摘要

Designers and builders focused on green innovations often struggle to know well the costs and benefits of their proposed projects. As such, some are reluctant to innovate beyond the well known, as even modest projects are costly in nearly all respects. This project is designed to provide data to promote actionable recommendations and strategic decision criteria for commercializing a model for exterior wall assemblies constructed with straw bales and earthen plasters. The wall assemblies are specific for houses built in hot arid climates using vernacular architecture and site-available earthen soils that take into account resiliency, environmental and social accountability, and affordability. These data derive from secondary research, four case studies, and two experimental build projects. A Full Costs Accounting (FCA) framework and Benefit Costs Analysis (BCA) assess costs, impacts, and benefits for the two experimental build projects that used the same amount of building material as measured in cubic feet (+/- 3%) but were constructed from different materials and design strategies for exterior wall assemblies. Results from the builds' FCA indicate that imported materials needed for a conventional wood framed wall assembly used 204% more fuels in the production process (cradle-to-factory gate) and 733% more diesel fuels in the transportation process (factory gate-to-retail store) than a vernacular build's wall assembly. Upfront labor costs were increased by 287% when using site-available soils for earthen plasters instead of imported lumber for a conventional wall assembly. Benefits (BCA) for the straw bale and earthen plaster construction include reduced impacts upon the extraction site, increased resiliency and social cohesion, and limited requirements for capital investments. This research contributes to the assessment tools available for stakeholders to make more informed decisions when investing in multi-faceted affordable housing projects in hot arid regions throughout the world.