At SimBuild 2024, we published our paper entitled “Minimizing Operational Carbon Within Whole Life Carbon for New Construction”. That study utilized DOE/PNNL prototype models over a 28-yr period using hourly NREL Cambium data through 2050 along with the embodied carbon of the structure and envelope. We also included annual refrigerant leakage and lifetime water-related carbon emissions per ASHRAE Standard 240P. We then overlaid numerous carbon reduction strategies such as electrification, cold-climate heat pumps, battery storage, on-site renewables, mass timber construction and building reuse along with lower GWP-refrigerants for two different building types in five different US cities in different climate zones to assess the whole life carbon impacts of these designs.

In the two years since then, MEP 2040 has made strides in bringing the embodied carbon of heating, ventilation, air-conditioning, electrical, telecom, fire protection and vertical transportation systems to the public’s attention. MEP 2040 published their first Beginner’s Guide in 2025 which leveraged methodologies from CIBSE, ASHRAE and RICS, which we used in our 2024 paper. ASHRAE Standard 240P is still in draft but has published a newer version with updated uncertainty calculations which govern the quality of the data being assessed. This session is an update with these recent developments using our prior models while pulling in MEP-embodied carbon with uncertainties and extending the assessment duration to the 60-yr standard reference study period.

With an aspiration to understand the nuances between carbon and cost over the lifespan of a building, this multiyear research project between Gensler, Buro Happold and Skanska focused on comparing simulated operational carbon metrics, simulated embodied carbon metrics, construction cost metrics and operational cost metrics on a multistory spec office building prototype that was "transplanted" to three US locations in three different climates zones (Houston TX, Washington DC and Boston MA) over a lifespan of 60 years. As a comparative effort, the prototype building was brought to current energy code level as a starting baseline and subsequently was optimized with commonly understood energy efficiency measures adapted to each of the locations. Then, we analyzed the baseline and "moonshot" models against operational carbon (including possible decarbonization rates of each utility grid as well as using future weather files per climate change IPCC scenario), embodied carbon (including rates of replacement of all building elements as well as the embodied carbon of MEP equipment over the lifespan of the building), operational energy costs (adjusted to local utility rates costs and inflation adjustments) and construction costs (adjusted to local conditions such as labor costs). The research relied heavily on energy simulation technology and embodied carbon analyses and workflows, providing a great understanding on the validity of preconceived assumptions on carbon optimization. It also provided a robust challenge to using Annual Energy Use as catch all metric for measuring the fitness of a building when considering its impact on climate change causing emissions. Finally, it provided great data on the return of investment of ambitious decarbonization strategies when measured against time and against local circumstances.

Large-scale infrastructure projects such as aviation facilities and Data centers present unique challenges for life cycle assessment (LCA) due to their scale, material intensity, and complex system integration. While operational energy has traditionally dominated sustainability and simulation efforts for these building types, embodied carbon from structural systems, enclosure assemblies, mechanical, electrical, and plumbing (MEP) systems, and civil works represents a significant and often under-quantified portion of total environmental impact.

As embodied carbon analysis gains traction in practice, critical questions remain unresolved, particularly for complex infrastructure projects. Which systems should be included to meaningfully represent embodied carbon? How should practitioners address limited or inconsistent environmental product data, especially for MEP systems and specialized infrastructure components? And how reliable are BIM-based quantity take-offs compared to contractor or supplier-provided data when results are used to inform early design decisions?

This presentation examines large-scale infrastructure case studies to illustrate how embodied carbon outcomes vary depending on the inclusion or exclusion of specific materials and equipment. The analyses are conducted in accordance with ISO 14040/44, modeling life-cycle stages A1–C4 using BIM-derived quantities and manufacturer-specific Environmental Product Declarations (EPDs) where available. System boundaries are intentionally adjusted across case studies to reflect differences in data availability.

The results demonstrate the extent to which scope definition and data quality influence LCA results and their reliability for informing design decisions. Based on these findings, the presentation proposes a phase-based framework to support IBPSA practitioners in aligning embodied carbon modeling effort with project phase, data maturity, and acceptable levels of uncertainty.

This study examines the application of energy modeling and life-cycle cost analysis (LCCA) to support HVAC system selection for a high-performance building. The primary goals were to (1) achieve a minimum 30% reduction in energy use compared to the ASHRAE 90.1-2019 baseline, and (2) determine the HVAC alternative with the lowest net present value (NPV) over its life cycle. In collaboration with the mechanical engineering team, four HVAC system configurations were evaluated:

• Proposed: Air-to-air heat pump

• ECM-1: Air-to-water heat pump with underslab radiant heating and cooling

• ECM-2: Ground-source heat pump with underslab systems

• ECM-3: Direct expansion (DX) cooling and gas heating system

Energy simulations quantified the energy use intensity (EUI) for each option, while a parallel LCCA estimated capital, operational, and maintenance costs over the study period of 40 years.

Simulation results indicated that only ECM-1 and ECM-2 met the energy reduction target, achieving 43% and 47% EUI reductions, respectively. These findings informed early design decisions by narrowing the field to high-performing, code-compliant systems aligned with the project’s sustainability goals. In contrast, ECM-3, while offering the lowest NPV due to its low upfront cost and comparable operational expenses, failed to meet energy performance requirements and was eliminated from consideration.

Among the compliant options, ECM-2 had slightly better energy performance and a nearly identical NPV to ECM-1. However, its implementation was associated with environmental and site-related risks, including excavation complexities, potential ledge, and concerns over PFAS contamination. These uncertainties, along with organizational budget constraints, shifted client preference toward ECM-1 for its reduced risk profile and practical feasibility.

The comparison between systems highlighted the trade-offs between cost-efficiency and sustainability. For example, despite ECM-3’s $2.1 million lower NPV compared to the proposed system, its higher energy use disqualified it. Meanwhile, the selection between ECM-1 and ECM-2 was shaped more by site conditions than by performance metrics. The modeling process played a pivotal role in communicating these trade-offs to stakeholders, enabling data-driven decision-making and alignment with client priorities.

This study demonstrates how simulation and life-cycle cost analysis can effectively guide real-world HVAC system selection in high-performance building design. By combining simulation results with financial evaluation, the team established a structured decision-making framework that balanced sustainability targets, long-term costs, and project feasibility. The collaborative process ensured that the selected system—ECM-1—not only met performance goals but also addressed implementation risks, reflecting a well-rounded and client-responsive design strategy.

Materials play a critical role in green building performance and occupant health, as they represent one of the primary interfaces between people and the built environment. As the green building industry has evolved, advancements in material technology and changing perspectives within building science have significantly reshaped how sustainability is defined and evaluated.

Certification systems such as LEED have guided this transition, particularly through the Materials and Resources credits. Over time, these requirements have become more rigorous, with an increased emphasis on environmental impact, transparency, and human health. Low-emitting materials, in particular, have remained a central focus, recognizing that occupants spend nearly 90% of their time indoors and are directly affected by material emissions.

With the introduction of LEED v5, the U.S. Green Building Council has further realigned its priorities in response to climate change and global sustainability goals and how the mind set has been reshaped into the certification process throughout the modern construction world by time. This version introduces notable changes in how materials are evaluated, including updated calculators, revised compliance pathways, and a stronger emphasis on emissions reduction and lifecycle impacts.

This presentation will examine the evolution of material-related requirements from LEED v4 to LEED v5 on a real project, with a specific focus on low-emitting materials. It will highlight key changes in methodology, discuss implications for designers, engineers, and consultants, and provide practical insights for navigating the updated requirements in real-world projects. Attendees will gain a clear understanding of how to interpret the updated calculators compared to the previous calculator versions, and how the process has been changed for the consultants to avoid common compliance pitfalls, and make informed material decisions that support both occupant health and project certification goals during the construction and design phases.