Impact of Lifetime on U.S. Residential Building LCA Results

Purpose: Many life cycle assessment (LCA) studies do not adequately address the actual lifetime of buildings and building products, but rather assume a typical value. The goal of this study was to determine the impact of lifetime on residential building LCA results. Including accurate lifetime data into LCA allows a better understanding of a product’s environmental impact that would ultimately enhance the accuracy of LCA results. Methods This study focuses on refining the U.S. residential building lifetime, as well as lifetime of interior renovation products that are commonly used as interior finishes in homes, to improve LCA results. Residential building lifetime data that presents existing trends in the U.S. was analyzed as part of the study. Existing data on product emissions were synthesized to form statistical distributions that were used instead of deterministic values. Product emissions data were used to calculate life cycle impacts of a residential model that was based on median U.S. residential home size. Results were compared to existing residential building LCA literature to determine the impact of using updated, statistical lifetime data. A Monte Carlo analysis was performed for uncertainty analysis. Sensitivity analysis results were used to identify hotspots within the LCA results. Results and discussion Statistical analysis of U.S. residential building lifetime data indicate that average building lifetime is 61 years and has a linearly increasing trend. Interior renovation energy consumption of the residential model that was developed by using average U.S. conditions was found to have a mean of 220 GJ over the life cycle of the model. Ratio of interior renovation energy consumption to pre-use energy consumption, which includes embodied energy of materials, construction activities, and associated transportation was calculated to have a mean of 34% for regular homes and 22% for low-energy homes. Ratio of interior renovation to life cycle energy consumption of residential buildings was calculated to have a mean of 3.9% for regular homes and 7.6% for low-energy homes. Conclusions Choosing an arbitrary lifetime for buildings and interior finishes, or excluding interior renovation impacts introduces a noteworthy amount of error into residential building LCA, especially as the relative importance of materials use increases due to growing number of low-energy buildings that have lower use phase impacts

A Hybrid Life Cycle Assessment Model for Construction Processess

This research qualitatively and quantitatively examined the environmental impacts due to the construction phase of commercial buildings. Previous building research often overlooked the construction phase and focused on the material and use phases, discounting the significant environmental impacts due to construction. The research was conducted using life cycle assessment (LCA) methodology, which is a systematic environmental management tool that analyzes and assesses holistically the environmental impacts of a product or process. This research contributed to further developing LCA research by focusing efforts on hybrid LCA modeling. The context of this research was established through examining green building rating systems, policy review, and project delivery methods with respect to the modeled results. Documented life cycle inventory results focused on PM emissions, GWP, SOx, NOx, CO, Pb, non-methane VOCs, energy usage, and solid and liquid wastes. Results compared with the entire building life cycle indicated that construction, while not as significant as the use phase, is as important as the other life cycle stages. In terms of hybrid LCA modeling, the augmented process based LCA proved to be effective in modeling the construction phase and allowed for efficiently combining process and input-output inventories. Including input-output results, especially construction service sectors, is critical in construction LCA modeling. One case study's results demonstrated that services had the highest level of methane emissions and were a significant contributor to CO2 emissions. Recommendations are made in terms of green building rating systems and national policies, including placing higher significance on construction activities within the United States Green Building Council's Leadership in Energy and Environmental Design (LEED) green building rating system

Application of Machine Learning for Predicting Building Energy Use at Different Temporal and Spatial Resolution under Climate Change in USA

Given the urgency of climate change, development of fast and reliable methods is essential to understand urban building energy use in the sector that accounts for 40% of total energy use in USA. Although machine learning (ML) methods may offer promise and are less difficult to develop, discrepancy in methods, results, and recommendations have emerged that requires attention. Existing research also shows inconsistencies related to integrating climate change models into energy modeling. To address these challenges, four models: random forest (RF), extreme gradient boosting (XGBoost), single regression tree, and multiple linear regression (MLR), were developed using the Commercial Building Energy Consumption Survey dataset to predict energy use intensity (EUI) under projected heating and cooling degree days by the Intergovernmental Panel on Climate Change (IPCC) across the USA during the 21st century. The RF model provided better performance and reduced the mean absolute error by 4%, 11%, and 12% compared to XGBoost, single regression tree, and MLR, respectively. Moreover, using the RF model for climate change analysis showed that office buildings’ EUI will increase between 8.9% to 63.1% compared to 2012 baseline for different geographic regions between 2030 and 2080. One region is projected to experience an EUI reduction of almost 1.5%. Finally, good data enhance the predicting ability of ML therefore, comprehensive regional building datasets are crucial to assess counteraction of building energy use in the face of climate change at finer spatial scale

Investigation of the Relationship between Green Design and Project Delivery Methods

The selection of the project delivery method (PDM) for any project is critical--it establishes communication, coordination, and contractual issues between the owner, contractor, and designer. With an increase in the number of green design projects, understanding the relationship between the PDM and green design is paramount to project and contract management. It is reasonable to assume that a positive relationship between green design and design-build (DB) exists since both theoretically are intended to foster an integrated, holistic, and collaborative project. This research examines the relationship between the design-bid-build (DBB), construction management (CM), and DB PDMs and green design with the goal of establishing best practices and identifying potential synergies between them. The research collected information by conducting primarily telephone interviews with approximately twenty-five individuals, including owners, contractors, and designers involved in completed green design projects, mainly in the public sector. The interviews developed a general understanding of the current state of knowledge and experience and not a rigorous quantitative analysis. Upon completion of the interviews, the tabulated results were summarized and green project characteristics and project-PDM interactions emerged. Existing published research was evaluated to reveal aspects of PDMs independent of green design. Best practices were ascertained by combining information from the interviews and published research. Best practices are as follows: (1) Project implementation features--The decision to use DB as PDM on green design or other projects should be based on the specific project features; e.g., well-defined scope and adequate owner staffing. DB will not produce successful results on all projects. (2) Collaboration--Project team collaboration early in the design and construction process is an important aspect of green projects, and collaboration was considered somewhat more important in projects that used DB. (3) Experience--Team experience is important on all green design projects independent of the PDM. Owners should use a 'best value' selection process, which is more prevalent in DB projects, and include team experience as a criterion. The owner's role is critical with DB. (4) Leadership--Leadership is an important feature for all contracting parties involved in green design projects and it is a dominant success factor in DB projects. (5) Scope of work--A well-defined scope of work is important on all projects, independent of the PDM. In DB, improving the scope of work definition by developing a set of documents, typically comparable to the design development phase, as the basis for awarding a contract is called DB bridging. Using contracting techniques such as DB bridging can result in better identification of expected quality and improves the owner's level of control. (6) Funding and Budget--Having adequate funding and budget for the given scope of work is particularly important in a green design project. Public funding restrictions may not allow use of certain PDMs, and the nature of public funding streams may make non-traditional PDMs more difficult. (7) Complexity and Flexibility--Complexity and flexibility is a project feature that is more specific to green design projects and is more frequently associated with DB. (8) Control and Accountability--Control and accountability is a problem associated with DB more than with DBB. It is not specific to green design projects. DB Bridging can be used to offset the lack of control with traditional DB. The use of green design and DB is increasing and understanding the linkage between the two is important. This research has found that while linkages do exist, the owner needs to carefully consider all aspects of a green design project before making the decision of the most appropriate PDM

Investigation of Energy Modelling Methods of Multiple Fidelities: A Case Study

Building energy modelling has become an integral part of building design due to energy consumption concerns in sustainable buildings. As such, energy modelling methods have evolved to the point of including higher-order physics, complex interconnected components and sub-systems. Despite advances in computer capacity, the cost of generating and running complex energy simulations makes it impractical to rely exclusively on such higher fidelity energy modelling for exploring a large set of design alternatives. This challenge of exploring a large set of alternatives efficiently might be overcome by using surrogate models to generalize across the large design space from an evaluation of a sparse subset of design alternatives by higher fidelity energy modelling or by using a set of multi-fidelity models in combination to efficiently evaluate the design space. Given there exists a variety of building energy modelling methods for energy estimation, multi-fidelity modelling could be a promising approach for broad exploration of design spaces to identify sustainable building designs. Hence, this study investigates energy estimates from three energy modelling methods (modified bin, degree day, EnergyPlus) over a range of design variables and climatic regions. The goal is to better understand how their outputs compare to each other and whether they might be suitable for a multi-fidelity modelling approach. The results show that modified bin and degree day methods yield energy use estimates of similar magnitude to each other but are typically higher than results from EnergyPlus. The differences in the results were traced, as expected, to the heating and cooling end-uses, and specifically to the heat gain and heat loss through opaque (i.e., walls, floors, roofs) and window surfaces. The observed trends show the potential for these methods to be used for multi-fidelity modelling, thereby allowing building designers to broadly consider and compare more design alternatives earlier in the design process

Do single-use medical devices containing biopolymers reduce the environmental impacts of surgical procedures compared with their plastic equivalents?

Background: While petroleum-based plastics are extensively used in health care, recent developments in biopolymer manufacturing have created new opportunities for increased integration of biopolymers into medical products, devices and services. This study compared the environmental impacts of single-use disposable devices with increased biopolymer content versus typically manufactured devices in hysterectomy. Methods: A comparative life cycle assessment of single-use disposable medical products containing plastic(s) versus the same single-use medical devices with biopolymers substituted for plastic(s) at Magee-Women’s Hospital (Magee) in Pittsburgh, PA and the products used in four types of hysterectomies that contained plastics potentially suitable for biopolymer substitution. Magee is a 360-bed teaching hospital, which performs approximately 1400 hysterectomies annually. Results: There are life cycle environmental impact tradeoffs when substituting biopolymers for petroplastics in procedures such as hysterectomies. The substitution of biopolymers for petroleum-based plastics increased smog-related impacts by approximately 900% for laparoscopic and robotic hysterectomies, and increased ozone depletion-related impacts by approximately 125% for laparoscopic and robotic hysterectomies. Conversely, biopolymers reduced life cycle human health impacts, acidification and cumulative energy demand for the four hysterectomy procedures. The integration of biopolymers into medical products is correlated with reductions in carcinogenic impacts, non-carcinogenic impacts and respiratory effects. However, the significant agricultural inputs associated with manufacturing biopolymers exacerbate environmental impacts of products and devices made using biopolymers. Conclusions: The integration of biopolymers into medical products is correlated with reductions in carcinogenic impacts, non-carcinogenic impacts and respiratory effects; however, the significant agricultural inputs associated with manufacturing biopolymers exacerbate environmental impacts

What works? Sustainability grand challenges in engineering curricula via experiential learning

Today’s complex global problems necessitate engineering solutions that not only consider sustainability, but include elements of design and creativity. Unfortunately, many engineering programs do not train students to think in terms of multiple contexts and at various scales. We often constrain students’ creativity to think within the narrow parameters of their specialization. Engineering educators face a difficult task of training students with both technical competencies and sustainability consciousness to tackle 21st century challenges. If we are to positively contribute to society, then we need to fundamentally change the way scientists, social scientists, and engineers are educated (Bielefeldt 2013). Two successful models for implementing sustainability grand challenges into engineering curricula have emerged in practice and in literature: stand-alone courses versus modules that are integrated into many courses. Engineering programs implement the stand-alone course-based model by establishing one to two distinct courses designed to address sustainability grand challenges and design in depth. One example of this is senior design. Conversely, engineering programs implement the modular-based model by integrating sustainability grand challenges and design throughout a host of existing courses and weave student exposure throughout the curriculum. These modules can be via ready-made modules, but more often than not faculty develop their own modules. The goal of this research was to evaluate the two models for implementing sustainability and to provide succinct recommendations and lessons learned for engineering programs tasked with integrating sustainability into their curricula. We review the implementation results of three sustainability courses, fourteen sustainability-themed modules, and senior design. We track progress towards responding to ABET Program Criterion related to sustainability and Civil Engineering Body of Knowledge 2nd edition (BOK2) Outcome 10: Sustainability. Results compare outcomes of students’ senior design project from universities implementing the two different approaches. And finally, we present the results of a formative and summative surveys of hundreds of students who participated in classes implemented throughout the project as well as faculty perceptions and barriers to implementation

On-Site Renewable Energy and Green Buildings: A System-Level Analysis

Adopting a green building rating system (GBRSs) that strongly considers use of renewable energy can have important environmental consequences, particularly in developing countries. In this paper, we studied on-site renewable energy and GBRSs at the system level to explore potential benefits and challenges. While we have focused on GBRSs, the findings can offer additional insight for renewable incentives across sectors. An energy model was built for 25 sites to compute the potential solar and wind power production on-site and available within the building footprint and regional climate. A life-cycle approach and cost analysis were then completed to analyze the environmental and economic impacts. Environmental impacts of renewable energy varied dramatically between sites, in some cases, the environmental benefits were limited despite the significant economic burden of those renewable systems on-site and vice versa. Our recommendation for GBRSs, and broader policies and regulations, is to require buildings with higher environmental impacts to achieve higher levels of energy performance and on-site renewable energy utilization, instead of fixed percentages