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The relative environmental impact from the building construction phase is increasing compared to the operation phase for new buildings. Therefore, it is important to consider the complete environmental life cycle of energy improvement measures. Many advanced optimization methods have been developed in recent years to assess building life cycle impact. However, these previous studies have not fully addressed the secondary effects, in other words, indirect effects outside the actual design option. This may lead to conclusions of optimization studies based on misleading calculation results. The main purpose this study was to highlight the relevance of including secondary effects in optimization of building design with respect to global warming potential and cost. This was done by conducting a parameter study of the building envelope insulation thickness with regard to global warming potential and life cycle costs, while considering secondary effects induced by the different design options. Findings from this study show that secondary effects influence the system boundary, algorithm architecture, results and the final conclusions of optimal building design. Omitting secondary effects can thus lead to incorrect decision on optimal solutions with regard to global warming potential and life cycle cost. Therefore, it is therefore important to take them into consideration when performing optimization studies of building design options. [ABSTRACT FROM AUTHOR]

Life cycle assessment and life cycle cost analysis are suitable tools in trying to minimize environmental impact and cost. To get reliable results it is crucial to set up correct system boundaries for the investigation, but it is often difficult to understand a complex products system because of the cascade effects of consequences that can be induced even by small changes. In this paper the effects and consequences evaluation (ECE) method is introduced to systematically identify and organize the effects and consequences for a design change of parts of a complex system. The method is applied in a case study of external wall insulation for a new building to investigate the importance of correct system boundaries. Using the methodical approach in identifying all significant consequences showed that unexpected unit processes can be important when deciding on the relevant system boundary. We also conclude that such processes can have a significant impact on the final results by calculating the change in global warming potential and life cycle cost for the processes affected by the design option. [ABSTRACT FROM AUTHOR]

In order to mitigate global warming, it is important to decrease the climate impact from the building stock, which accounts for 39% of the GHG emissions in Europe. An extensive portion of these emissions are generated from the heating of buildings, but emissions also occur from the production of building materials. It is therefore important to find building design solutions that consider both production and operation and maintenance in order to minimise the climate impact of a building during its entire lifetime. At the same time, the production of buildings has to be cost-efficient. In the design of buildings, both climate impact and cost must be evaluated in order to make well-supported decisions. The overall aim of this study was to develop a procedure to facilitate using life cycle studies as decision support for building design. The presented approach will provide a structured means to manage choice and parameter uncertainty when life cycle studies are used as decision support in order to optimise building design. There are many uncertainties in the design phase of buildings, and the approach is demonstrated here in a case study of insulation thickness in the building envelope. The results can be used to support decisions on where to effectively make improvements when subjective choices and parameter uncertainties are considered in the study. The suggested approach will lessen the problem of false certainty in the conclusions drawn, and at the same time provide strong decision support. • The study shows how to incorporate ECE and DCP in simulation of building design. • The approach manages secondary effects and uncertainties in life cycle tools. • Mitigate the risk for faulty conclusions regarding optimal building design. [ABSTRACT FROM AUTHOR]

As life cycle assessments are often conducted to provide decision support, it is important that impact assessment methodology is consistent with the intended decision context. The currently most used climate impact assessment metric, the global warming potential, and how it is applied in life cycle assessments, has for example been criticised for insufficiently accounting for carbon sequestration, carbon stored in long-lived products and timing of emission. The aim of this study is to evaluate how practitioners assess the climate impact of forest products and the implications of method choice for results and decision-making. To identify current common practices, we reviewed climate impact assessment practices in 101 life cycle assessments of forest products. We then applied identified common practices in case studies comparing the climate impact of a forest-based and a non-forest-based fuel and building, respectively, and compared the outcomes with outcomes of applying alternative, non-established practices. Results indicate that current common practices exclude most of the dynamic features of carbon uptake and storage as well as the climate impact from indirect land use change, aerosols and changed albedo. The case studies demonstrate that the inclusion of such aspects could influence results considerably, both positively and negatively. Ignoring aspects could thus have important implications for the decision support. The product life cycle stages with greatest climate impact reduction potential might not be identified, product comparisons might favour the less preferable product and policy instruments might support the development and use of inefficient climate impact reduction strategies. [ABSTRACT FROM AUTHOR]