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Purpose Building life cycle assessment (LCA) draws on a number of indicators, including primary energy (PE) demand and global warming potential (GWP). A method of constructing a composite index of weighted individual indicators facilitates their use in comparisons and optimization of buildings, but a standard for weighting has not been established. This study investigates the use of monetary valuation of building LCA results as a way to weigh, aggregate, and compare results. Methods A set of six recent German office buildings served as a case study. For these, standard LCA and life cycle cost (LCC) calculations were conducted. Monetary valuation models from the literature were investigated as a basis for evaluation. From these, maximum and minimum valuation was chosen and applied to the LCA results for the embedded impacts of the case study buildings. The buildings' environmental costs (EC) were thereafter calculated and contributions of single impacts are analyzed. The EC-based on external costs-are subsequently compared with the life cycle costs (LCC)-based on market prices-of the respective buildings. Results and discussion Of the five standard environmental indicators used in Germany, GWP contributes approximately 80 to 95% of the overall EC. Acidification potential (AP) is the second largest contributor with up to 18%. Eutrophication (EP), photochemical oxidization (POCP), and ozone depletion potential (ODP) contribute less than 2.0%, 1.05%, and 2.4E−6% respectively. An additional assessment of the contribution of resource depletion to EC shows an impact at least as large as the impact of GWP. The relation between the EC and LCC strongly depends on the EC model used: if EC are internalized, they add between 1 and 37% to the life cycle costs of the buildings. Varying construction materials for a case study building shows that materials with low GWP have the potential to lower environmental costs significantly without a trade-off in favor of other indicators. Conclusions Despite their sensitivity to the monetary valuation model used, EC provide an indication that GWP and resource depletion-followed by AP-are the most relevant of the environmental indicators currently considered for the construction industry. Monetary valuation of environmental impacts is a valuable tool for comparisons of different buildings and design options and provides an effective and valuable way of communicating LCA results to stakeholders.

The early stages of building design involve the consideration of different design variants and their assessment regarding various performance criteria including energy consumption and costs. During the design process, the involved experts from different disciplines frequently exchange building information to develop a design that satisfies the project’s requirements and objectives. In the course of this iterative process, the building design evolves throughout multiple refinement stages. At the same time, different variants are developed. In BIM-based projects, the maturity of the design information provided by the model is expressed by the notion of Level of development (LOD). So far, however, there is no method to formally define the information requirements of a LOD. In particular, there are no means for expressing the uncertainty involved with the provided information. By contrast, despite the insufficient information available in early design stages, a BIM model appears precise and certain. This situation leads to false assumptions and model evaluations, for example, in the case of energy efficiency calculations or structural analysis. Hence, this paper presents an overview of a set of approaches that were developed to alleviate and preserve the consistency of the designed solutions. The approach includes the development of a multi-LOD meta-model, which allows one to explicitly describe the LOD requirements of each building component type incorporating the possible uncertainties, e.g. concerning the building dimensions. On the basis of this multi-LOD model, methods for evaluating a building design’s performance regarding the building’s structure and life cycle energy performance are proposed that take the defined uncertainties into account. To support the management of design variants in one consistent model, a graph-based approach is introduced. Finally, a minimized communication protocol is described to facilitate the workflow and communicate the evaluation results for supporting the decision-making process.

With current efforts to increase energy efficiency and reduce greenhouse gas (GHG) emissions of buildings in the operational phase, the share of embedded energy (EE) and embedded GHG emissions is increasing. In early design stages, chances to influence these factors in a positive way are greatest, but very little and vague information about the future building is available. Therefore, this study introduces a building information modeling (BIM)-based method to analyze the contribution of the main functional parts of buildings to find embedded energy demand and GHG emission reduction potentials. At the same time, a sensitivity analysis shows the variance in results due to the uncertainties inherent in early design to avoid misleadingly precise results. The sensitivity analysis provides guidance to the design team as to where to strategically reduce uncertainties in order to increase precision of the overall results. A case study shows that the variability and sensitivity of the results differ between environmental indicators and construction types (wood or concrete). The case study contribution analysis reveals that the building’s structure is the main contributor of roughly half of total GHG emissions if the main structural material is reinforced concrete. Exchanging reinforced concrete for a wood structure reduces total GHG emissions by 25%, with GHG emissions of the structure contributing 33% and windows 30%. Variability can be reduced systematically by first reducing vagueness in geometrical and technical specifications and subsequently in the amount of interior walls. The study shows how a simplified and fast BIM-based calculation provides valuable guidance in early design stages.

With increasing environmental damage and decreasing resource availability, sustainability assessment in the building sector is gaining momentum. A literature review shows that the related methods for environmental and economic performance, Life Cycle Assessment (LCA) and Life Cycle Costing (LCC), show great potential for answering a multitude of questions related to building performance. Prevalent topics are the implications of LCA and LCC for retrofit solutions and the trade-offs between environmental and economic considerations in building design. A detailed review of 30 case studies shows the range of differing result integration methods and sheds light on the use of monetary valuation of environmental indicators for an integrated assessment. While a quasi-dynamic approach, accounting for the changing value of money over time, is common in LCC, such an approach is largely absent from LCA. The analysis of common metrics shows that the studies employ strongly differing system boundaries and input parameters. Moreover, a clear description of the methodological framework is missing in most studies. Therefore, this research develops an “Eco2” framework, integrating LCA and LCC for application in building design. Potential further developments for Eco2 building assessment are related to extending the system boundaries by including mechanical systems and end-of-life phases, data collection and structuring, and streamlining the approach for continuous application to all stages of building design processes. Additionally, the influence on design decisions of employing temporal parameters in both LCA and LCC and of choosing particular result integration methods should be investigated further.