Methodology for Life-Cycle Sustainability Assessment of Building Structures

American Concrete InstituteACI Structural Journal March/April 2017Methodology for Life-Cycle Sustainability Assessment of Building Structuresby M. C. Caruso, C. Menna, D. Asprone, A. Prota, and G. Manfredi

Newswise — The design of new structures, as well as the retrofit strategies of existing buildings, have become the preferential target of contemporary engineers and architects for achieving sustainability goals in the construction industry.

This paper defines a methodological framework, through case study, that can be used as a guide to construction community stakeholders for conducting environmental sustainability comparisons among building systems, providing equivalent performances at the design stage as well.

Over the past few decades, our society has witnessed a growing attention to topics related to sustainable development¹. Global warming, increased localization of human diseases, and impoverished nonrenewable resources have led society to focus on reducing the environmental impact generated by human activity. Among these, construction and related industries play a major role with regard to global challenges, as they are widely recognized as having a significant global impact on the environment.

Specifically, many assessment tools have been developed to effectively drive decision-making processes in the direction of minimizing environmental loads associated with construction activities. Some methodological frameworks analyze single or multiple aspects of environmental scenarios that are related to construction activities. Other methodologies, based on a life-cycle assessment (LCA) (ISO 14040²) approach, have the potential to analyze overall environmental factors related to the entire life cycle of a material or structure, or of a building component. By performing an LCA of a general product, it is possible to quantify its impact on the environment.  This assessment is not limited to only energy or CO2 emissions. It also includes the use of other renewable and nonrenewable resources, including the emission of many organic and nonorganic compounds into the air, water, and soil, and the effects of ionizing radiation.

The methodologic framework in the study proposed by the authors is based on awareness that the design of new structures starts with specific requirements, including national technical standards. During the design stage, the component/building structural performance is the main “parameter” that drives the designer, along with the subsequent need to satisfy structural codes and guidelines. This performance requirement is related to many other initial choices set by the customer, for example: location, final use, number of stories, available resources, and functional systems. All these requirements can lead to different optional design choices, which can be compared at this stage to provide the best solution.

Given these considerations, in the proposed approach we define a set of “building system requirements” for the building element/system, accounting for functional, architectural, structural, and economic performances, as well as other factors specifically defined by the end users of the buildings (refer to Figure 1, steps 1 to 2). These requirements are interconnected because the choice of one specific requirement can affect the others; for example, the definition of the use of the structure/building like residential, office, and strategic infrastructure, primarily affects the architectural, structural, and economic features linked to decision-making at the design phase. Moreover, some of the requirements are site-specific, and depend on the climatic zone and hazards, related to the geographical position of the building. Within this framework, the comparative evaluation of different design options can be effectively performed at the level of the final product system (assembly level), that is, the entire building/structure. In this way, the environmental effects associated with one or more subassembly options can be effectively regarded at a global level that is representative of the final product.

The feasible options are identified based on the fixed requirements, which first depend on building use and location in terms of live loads, hazards, and environmental condition, considering several additional constraints, such as common and local construction techniques and materials, overall cost, and national standards establishing minimum performances (Figure 1, step 3). Once the minimum design parameters are computed for all the options and the different building configurations designed, the building sustainability assessment can be performed using common sustainability tools (Figure 1, step 4). In this way, the proposed framework defines the system boundary that should be built to compare different products within a given building structure.

The described methodological approach used in the case study is depicted in Figure 2, where three building material options are compared –– reinforced concrete (RC), steel, and wood –– in relationship to the structural system of a residential building. Starting with functional, architectural, and structural requirements, the building is designed and verified to take into account how structural solutions change for each building material (Figure 3). A cradle-to-grave LCA study is conducted for the three alternative structures. The functional unit chosen for this analysis was the entire building and the estimated impacts were tied to the materials and processes needed to build the structural system. The system boundary is shown in Figure 4 and includes the:

1) Pre-use phases including extraction, and the production of materials and construction
2) Use phase, which is the ordinary maintenance of structural elements
3) End of life (EOL) phase including EOL, building demolition, and material disposal.

For each phase of the system boundary, environmental impacts are quantified by means of IMPACT2002³+ and EPD2008⁴ methodologies. Global results, which are shown in Figures 5 and 6, reveal that within this methodological framework, the RC option is an environmentally-worthy building solution. Indeed, when considering all the impact categories of IMPACT2002+ and EPD results, the RC structure has the highest impact for climate change but with the lowest for the other categories throughout the entire life-cycle of the building.

As a final remark of the methodology application, note there is no option that produces the best LCA-based environmental performance in all impact categories. As a consequence, a rigorous environmental analysis based on the proposed methodology can influence and orientate the decision-making process when it comes to defining the most sustainable design alternative with respect to one of the selected environmental categories.

The research can be found in a paper titled “Methodology for Life-Cycle Sustainability Assessment of Building Structures,” published by ACI Structural Journal.

¹United Nations Report of the World Commission on Environment and Development - Our common future, 1987

²ISO (2006) Environmental Management. Life cycle assessment. Principles and Framework EN ISO 14040

³Humbert S.,  De Schryver A., Bengoa X., Margni M., Jolliet O. IMPACT2002+ User Guide for vQ2 21 1 November 2012

⁴The International EPD Cooperation (IEC) Introduction, Intended uses and Key Program Elements for Environmental Product Declaration EPD. Version 1.0, 2008.

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