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Unlocking Sustainability in Building Systems: A Guide to Whole Life Carbon for MEP Systems

Unlocking Sustainability in Building Systems: A Guide to Whole Life Carbon for MEP Systems”

By Ghina Annan, M.Eng Applied Energy, CEM, LEED AP, WELL AP, LFA


Mechanical, electrical, and plumbing (MEP) systems are the lifeblood of buildings, ensuring occupant comfort and operational functionality. However, they also contribute significantly to a building's energy consumption and carbon emissions. Over the past two years, I have had the privilege of chairing the ASHRAE committee responsible for creating the "Whole Life Carbon for Building Systems" guide. The mission was clear: to create a comprehensive resource that would revolutionize the way we approach sustainability in building systems. Our dedicated committee worked tirelessly to craft a guide that empowers building professionals, from engineers to designers, operators to owners, to understand and reduce the entire building life cycle of greenhouse gas emissions.


How can we design MEP systems that pave the way for a sustainable future?


MEP systems are the central nervous system of buildings, sustaining occupants' health, productivity, and comfort. At the same time, they constitute a significant portion of a building's operational energy consumption and whole life greenhouse gas (GHG) emissions. Choosing MEP systems is akin to making a long-term commitment, affecting operational efficiency and sustainability. Therefore, a forward-looking approach must be taken to address current needs while anticipating future regulatory shifts, such as building performance standards.


Design professionals excel in creating MEP systems that meet performance requirements while reducing operational energy consumption. However, limited data and design guidance hinder efforts to quantify and mitigate the entire life cycle GHG emissions linked to MEP systems. These emissions encompass embodied carbon, operational emissions, end-of-life disposal, and optional reuse or recycle module. Studies reveal that embodied GHG emissions from MEP systems can constitute a substantial share of a building's total embodied emissions, emphasizing the need for holistic sustainability strategies.


Purpose and scope of the guideline


The guide aims to empower building engineers, designers, consultants, operators, manufacturers, and owners to understand and reduce whole life GHG emissions in MEP systems. It provides clear definitions of key systems, life cycle stages, and assessment methodologies while delineating roles and responsibilities for different stakeholders. While it's tailored to buildings in North America, it doesn't replace code compliance. It's essential to note that this guide does not offer calculations for energy consumption or GHG emissions nor set performance targets. Instead, it equips readers with the foundational knowledge needed to navigate the complex landscape of MEP whole life carbon.


What Are Embodied and Operational Carbon, and How Do LCAs Help?


A foundational understanding of terms like carbon dioxide equivalent emissions (CO2e), embodied carbon, and operational carbon is crucial. Embodied carbon covers emissions related to the production, transportation, construction, replacement cycles, refrigerant leakage and building material end of life, with optional reporting of reuse and recycle content—while operational carbon encompasses emissions arising from energy and water consumption. A Whole Life Cycle Assessment (WLCA) methodology is critical to quantify these emissions, ensuring that both embodied and operational emissions are considered.


LCA, following ISO standards, is a method to measure a built asset's environmental impact from raw material extraction to end of life. Metrics like Global Warming Potential (GWP) help evaluate climate change impacts. A typical LCA involves stages such as production, construction, use, end of life, and optional supplementary information, depending on the goal and standards. Building-Level LCAs (WBLCA) provide insights into the embodied carbon impact of entire buildings, including MEP systems. These assessments rely on high-quality Embodied Carbon Data Sources, often obtained from Environmental Product Declarations (EPDs).


The Impact of HVAC


HVAC systems play a pivotal role in a building's carbon emissions, with selected examples of 56% of weight and a staggering 74% of carbon emissions within MEP systems. The impact of HVAC systems can range from 15% to 36% of the total embodied carbon in commercial buildings. In the UK, they contribute up to 25% of the embodied carbon in residential buildings. Striking a balance between operational and embodied carbon is essential. Studies demonstrate that reductions in operational carbon can lead to an increase in embodied carbon, making the relationship complex.


What Are the Key Strategies for Reducing the Carbon Footprint of MEP Systems?


To achieve whole life carbon reduction, it's vital to reconsider design criteria, perform WBLCA studies, optimize equipment selection, reduce duct and pipe embodied carbon, minimize refrigerant impacts, track refrigerant usage, and quantify MEP material use. Reducing the carbon footprint of MEP systems requires using renewable or recycled materials, optimizing system designs for energy efficiency, and minimizing waste during construction. Quantifying MEP material use is a critical step in this journey. This guide opens doors to a sustainable future in building systems by providing the knowledge and guidance needed to design MEP systems with lower whole life GHG emissions. It emphasizes the critical importance of understanding the environmental impact of these systems from cradle to grave.