CIB W116—Smart and Sustainable Built Environments - Test Input

The following analysis describes the environmental burdens associated with constructing, occupying,
and removing residential buildings. Rather than isolate selected reusable and recyclable materials, as
in the study cited above, a whole-building scenario is more representative of mainstream construction
practices and impacts.
A single-family residential building was selected for this example because it is easily visualized by a
wide range of readers and audiences. However, the same principles apply to commercial and
institutional buildings. Furthermore, the analysis of one residential building can be extrapolated to
represent both the total annual residential debris burden in the U.S. and the potential benefits of
recovering materials for reuse. The LCA were performed using the Athena Impact Estimator for
Buildings. This software enables designers to develop and compare alternative designs..
Athena’s inventory analysis identifies the energy use, inputs, emissions, and waste involved with each
material, over each life-cycle phase. Inventories are described as energy inputs; air emissions; water
emissions; solid waste; and resource use. Inventory values are expressed in the total quantities of
each constituent element or compound present in the building.
Impact summaries represent the combined effects of the inventory, over all life-cycle phases. Impact
categories are described as: energy consumption; resource use; global warming potential; acidification
potential; eutrophication potential; ozone depletion potential; and smog potential.
5.1 Building models
In order to assess the impacts of using recovered building materials, instead of new materials, a simple
house design was developed. From this design, two models were developed for the Impact Estimator.
The first was a 2,800 square foot (260 square meter) two-story house of conventional wood framed
construction and brick veneer, constructed with all new materials. The second was an identical 2,800
square foot (260 square meter) house of identical wood frame and brick veneer construction
constructed using recovered materials for the following: 75% of the framing lumber; 50% of the
veneer bricks; 100% of the windows and doors; 75% of the finished flooring; 100% of the kitchen and
bathroom cabinets; and miscellaneous equipment. The quantities of recovered materials used are
optimistic but entirely reasonable. It is reasonable to assume that recovered materials would be of
equivalent performance to new materials. A 40-year life expectancy was designated for both models.
Based on user inputs for design configuration, dimensions, materials, and assemblies, the software
develops models of the design or alternates, identifies material types, and calculates quantities. The
software then applies its database to develop life-cycle impact analyses.
The Impact Estimator software was not designed specifically to assess the relative impacts of wasted
or recovered building materials. In order to represent a quantity of recovered materials, the quantity
of that material generated by the Impact Estimator was manually revised. Therefore, the
manufacturing inventories and impacts would represent only the new materials, and the end-of-life
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