Sustainable early design exploration of mid-rise office buildings with different subsystems using comparative life cycle assessment

Minimizing environmental impacts over a building’s life cycle is critical to achieving sustainable communities. Early design is the most critical step to improve construction’s sustainability, as the majority of important decisions have not yet been made. However, the implementation of sustainability assessment in early design is data- and effort-intensive, resulting in limited whole building life cycle assessments. Previous studies have mainly focused either on single residential structures, included only a subset of building components, or investigated early design parameters mostly associated with energy efficiency. Whereas, comparison of alternative building subsystems at early design received less attention. This study aims to provide and utilize benchmark data for the life-cycle impacts of mid-rise office buildings, focusing on the impact of building subsystem selection at early design exploration. Environmental impacts were compared across six professionally-designed archetypes comprising compatible combinations of foundation, floor, and structural assemblies for a site in Charleston, South Carolina. Detailed operational energy modeling was performed using the EnergyPlus framework, where a range of code-compliant envelope systems are studied and paired with other assemblies. Lastly, sensitivity assessment and statistical analysis are performed to quantify uncertainty associated with the use of such data for early design guidance. The results suggest that decisions associated with the use phase (such as envelope selection) dominates life cycle impacts and should be prioritized. Additionally, no single subsystem governs all embodied impacts across different buildings. Lastly, it is critical to consider a large number of alternatives at the early design stage, as excluding a combination of subsystems might close pathways to reaching a more environmentally suitable alternative during design iterations/optimization.

Novel Methodology for Sizing a Single U-Tube Ground Heat Exchanger Useful at the Early Design Stage

Renewable energy system (RES) is an environmentally friendly source of energy. A suitable design of RES is crucial to implement an energy-efficient building such as a zero energy building (ZEB). The significance of appropriate decision-making for the successful implementation of energy-efficient buildings has been increasing. In addition, the identification of the sizing of RES is equally important for architects or HVAC engineers. In this study, a novel sizing method for a single U-tube ground heat exchanger (GHE) is proposed. A transient thermal analysis for a single GHE is performed by considering ground temperature recovery effect as well as other major design parameters. The results are used to design the proposed sizing method and were verified by transient simulations for different design cases. Additionally, it was observed that the coefficient of variation of root mean square error (CV(RMSE)) for all ten design cases was lower than 15% during the heating and cooling seasons. Thus, the proposed design method can be used for sizing a GHE in the early design stage.

Architectural Models as a Base for Reliable Early Stage Energy Simulation

<p>Designers from the Architecture, Engineering, and Construction (AEC) industries have shown a desire to allow for quantitative data to back up sustainable decision-making (Braasch, 2016). Methods and software used to reach this goal often do not provide all the information to make informed design decisions or require a complete remodelling of designs at each stage. These factors make Building Performance Simulation (BPS) feasible at early design stages, where it is most beneficial for Architects. This thesis explores the current process to translate Architectural models constructed within a Building Information Modelling (BIM) environment into Building Energy Models (BEM) so that performance simulations can take place. Within the aim of exploring translation processes, the objectives were to document: • Whether current processes can facilitate modelling of environmental building performance during early design, as well as during developed design? • Whether there are any common problems or successful approaches that might form the basis of future improvements in the way Architect’s and consultant’s models work together? This thesis has identified 19 translation processes from current literature and examined a range of representative processes for exchanging information between Architectural modelling and BPS programs. It concluded that translation issues can be classified into similar groups based on the overall processes used. The eight categories of issues can be used by future developers to determine their priorities in development, and those looking for a current solution can adopt one for themselves. None of the processes tested allowed for issue-free modelling of building performance during sketch design. The two types of building translation schema evaluated in this thesis divided identified references between a dedicated and generalised approach. The dedicated approach of gbXML and the generic approach of IFC identified similar issues; however, IFC contained more of these problems because it communicates with all modelling programs at a lower information quality. Due to the generic approaches containing more issues that take longer to solve, it is currently more complicated to generate an energy model out of IFC data. While the gbXML schema can only provide benefits for BPS related translations, it is the most viable way to provide the service.</p>

Architectural Models as a Base for Reliable Early Stage Energy Simulation

<p>Designers from the Architecture, Engineering, and Construction (AEC) industries have shown a desire to allow for quantitative data to back up sustainable decision-making (Braasch, 2016). Methods and software used to reach this goal often do not provide all the information to make informed design decisions or require a complete remodelling of designs at each stage. These factors make Building Performance Simulation (BPS) feasible at early design stages, where it is most beneficial for Architects. This thesis explores the current process to translate Architectural models constructed within a Building Information Modelling (BIM) environment into Building Energy Models (BEM) so that performance simulations can take place. Within the aim of exploring translation processes, the objectives were to document: • Whether current processes can facilitate modelling of environmental building performance during early design, as well as during developed design? • Whether there are any common problems or successful approaches that might form the basis of future improvements in the way Architect’s and consultant’s models work together? This thesis has identified 19 translation processes from current literature and examined a range of representative processes for exchanging information between Architectural modelling and BPS programs. It concluded that translation issues can be classified into similar groups based on the overall processes used. The eight categories of issues can be used by future developers to determine their priorities in development, and those looking for a current solution can adopt one for themselves. None of the processes tested allowed for issue-free modelling of building performance during sketch design. The two types of building translation schema evaluated in this thesis divided identified references between a dedicated and generalised approach. The dedicated approach of gbXML and the generic approach of IFC identified similar issues; however, IFC contained more of these problems because it communicates with all modelling programs at a lower information quality. Due to the generic approaches containing more issues that take longer to solve, it is currently more complicated to generate an energy model out of IFC data. While the gbXML schema can only provide benefits for BPS related translations, it is the most viable way to provide the service.</p>

Method for holistic wind turbine drivetrain comparison exemplarily applied to geared and direct drive systems

The drivetrain as an important part of wind turbines needs to be improved in order to deal with today’s high development and cost pressure. One important step towards enhanced drivetrains is to identify the most suitable concept for a targeted onshore application in an early design stage. With this purpose, a holistic lifecycle system evaluation approach relying on minimum input information is presented. In order to identify a dominant solution, an additive target system is defined taking cost, ecological sustainability, and supplied energy into account. This multi-criteria decision is aggregated by defining a macrosocial evaluation criterion: “drivetrain specific energy supply effort”. A physics- and empirically-based model is developed to quantify the targets for different onshore drivetrain concepts. The validity of the model results is shown by a comparison to meta-analysis findings. Being utilized on a drivetrain concept comparison between geared and direct drive the approach’s value is showcased. Both concepts score on a comparable level slightly differing in weak and strong wind regimes. An exemplary trade-off between investment- and operational effort shows, that for both concepts the investment effort is higher than the operational. The comparison furthermore shows how robust decision support can be provided by parameter variation and finally it stresses, that the decision maker’s preferences need to be incorporated in the decision. Concluding, this analysis shows that physics- and empirically-based model approaches enable holistic wind turbine drivetrain concept comparisons in an early design stage.