Reducing Embodied Carbon in Building Systems: From Concept to Practice

By Ghina Annan
Associate and Decarbonization Business Lead at Stantec

The impact of MEP (Mechanical, Electrical, and Plumbing) systems on a building’s embodied carbon is substantial, accounting for 15% to 50% throughout the building’s lifespan. This impact can rise to 70% or more in commercial buildings undergoing retrofits, as highlighted in CLF’s tenant fit-out study.

The challenge of designing and specifying MEP equipment involves not only functional and operational efficiency but also minimizing the life cycle carbon footprint of these systems. My work involves supporting the industry in achieving national and global carbon reduction targets, including net zero and climate emission goals. Understanding and addressing embodied carbon in MEP systems is crucial. While Environmental Product Declarations (EPDs) are available for many building materials, there’s a notable gap regarding MEP equipment. To bridge this gap, the Chartered Institution of Building Services Engineers (CIBSE) developed TM65, a methodology to calculate the embodied carbon of building services.

Embodied Carbon: A Comprehensive View

In practical terms, embodied carbon encompasses all emissions up to the point where a building becomes operational, including materials, manufacturing, transportation, and construction processes. It also covers emissions from use, maintenance, repair, replacement, refurbishment, and demolition throughout the building’s lifecycle. Therefore, managing embodied carbon effectively requires understanding and optimizing every component of MEP systems. Three key drivers of MEP carbon impact are:

1. Replacement Frequency: Frequent upgrades or replacements can significantly increase embodied carbon due to the material and manufacturing processes involved.
2. Refrigerants: Choosing the right refrigerants is crucial, as they can have a high global warming potential if leaked.
3. Energy Production Systems: These systems must be designed efficiently to minimize their embodied carbon footprint.

Strategies for Reducing Embodied Carbon of MEP Systems

To effectively reduce the embodied carbon of MEP systems, consider the following actions:

1. Maximize Passive Solutions: Use natural ventilation, shading, and thermal storage to reduce reliance on mechanical systems. Enhance the building’s performance with a high-performance envelope.
2. Avoid Overengineering: Design systems to meet current needs with the potential for future upgrades rather than oversizing from the outset.
3. Understand Product Data: Specify products with lower embodied carbon by utilizing tools like TM65 and the One Click LCA MEP carbon tool.

Reducing duct or pipe sizes by increasing temperature differentials and using alternative materials like fabric or fiberglass can significantly lower embodied carbon. Smaller ducts and pipes require less material, which directly reduces the carbon footprint associated with their production and installation. Thermal storage systems, such as architectural thermal mass, phase change materials (PCMs), and active HVAC thermal storage, play a key role in energy efficiency. Architectural thermal mass involves using building materials that can absorb and store heat, helping to regulate indoor temperatures naturally. Active HVAC thermal storage systems store excess thermal energy during off-peak periods and release it during peak demand times, reducing the need for large central cooling plants. This not only lowers operational carbon emissions but also reduces the embodied carbon of the HVAC systems by minimizing the size and capacity of the equipment needed. Refrigerants, particularly hydrofluorocarbons (HFCs), are significant contributors to carbon emissions due to their high global warming potential (GWP). HFCs can be thousands of times more potent than carbon dioxide regarding their impact on global warming. Proper management and disposal of refrigerants, along with the adoption of low-GWP alternatives, are essential steps in reducing their environmental impact.

Importance of Standardized Assessments

Given the current immaturity of the industry in conducting whole-life carbon assessments (WLCAs), there is confusion about what should be included. In many assessments, MEP systems and externals are excluded from the scope. Yet these systems can prove to be a huge component of the overall embodied carbon emissions and should thus be a central factor in a meaningful WLCA. Quantifying MEP system material use involves tracking materials throughout design, construction, and operation to understand embodied carbon emissions and recycling potential. Methods include Material Takeoff, which lists materials from design specs, and Building Information Modeling (BIM), which uses 3D models to calculate material quantities and optimize sustainability. Standardized approaches and industry-wide agreements are essential for effective carbon reduction strategies. Access to accurate carbon emissions data remains challenging across industries. Ongoing research, involving manufacturers, contractors, consultants, and researchers, is improving however It’s important to document assumptions and data sources for future review and updates.

Balancing Carbon Reduction in Cost-Conscious, Time-Driven Projects

It’s imperative to evaluate costs comprehensively, from passive to active design and renewables, rather than focusing solely on material and system expenses. Business case analyses for resilient and sustainable buildings are essential to understand the multi-dimensional impacts on long-term investments, considering five- to ten-year horizons.

As a participant in the ASHRAE Center of Excellence for Building Decarbonization, I recognize that the scope of building-related policies, programs, and regulations needs to expand to incorporate deep energy efficiency improvements, beneficial electrification, demand flexibility, and whole building lifecycle greenhouse gas emission reductions. These outcomes need to be achieved concurrently with maintaining comfortable, healthy, safe, resilient, and affordable building environments for occupants. I encourage you to visit ASHRAE to know more. Additionally, I recommend reviewing the upcoming ASHRAE guides on the Whole Life Carbon of Building Systems et TM65 for North America, which I have contributed to. These resources provide invaluable insights and methodologies to help achieve significant carbon reductions. Moreover, député européen 2040 is an initiative aimed at reducing carbon emissions from building systems through collective action. I encourage firms to get involved and individuals to join the MEP 2040 working groups to help make a meaningful impact.

Finally, reducing embodied carbon and optimizing MEP systems requires a strong system- thinking framework, a clear roadmap with stretch targets, and a thorough business case analysis to understand the return on investment. Collaboration between manufacturers, designers, developers, researchers, investors, and involved stakeholders is essential to leverage rapid technological advancements for whole-life carbon reduction.

Thank you and best regards,

Ghina