Over the past decade, the industry focus has been on reducing the carbon emissions from building operations. First, we model the energy used in building operations. Then we implement energy efficiency strategies to reduce them. The building design industry has made great strides in energy efficiency and reducing operational carbon.

This success in reducing the energy appetites of buildings highlights the role of embodied carbon. And it remains a major contributor to total building emissions, as much as 50 percent.

As we drive toward decarbonization, the industry is now focusing on reducing the emissions associated with the building materials and construction.?Most embodied carbon emissions occur before the building is open. Operational carbon emissions, on the other hand, occur year on year. We can implement energy-efficiency measures over the building life cycle to reduce these emissions. But with embodied carbon, once we design it and procure the materials, the embodied carbon emissions are locked in.

There is no going back.

Taking buildings on a journey toward net zero carbon requires that we take a sequential approach. This helps us make the critical decisions at the right point in the design process.

To see the total carbon impact of the building over its life we need to understand embodied carbon. The buildings industry needs to focus on embodied carbon emissions right now. The global construction industry will double in size over the next 40 years, and if we¡¯re not focused on embodied carbon, we won¡¯t hit targets in the Paris Agreement.

The LCA is a step in the right direction.

Life cycle assessments come in a variety of forms

Honestly, we need to start the LCA early. It helps clients know the carbon impact from materials. To get the full value from an LCA and implement design strategies related to life cycle, the LCA should be integrated into whole-building design through the planning, predesign, design, construction, and occupancy phases.

We recently did an LCA for a buildings project where our client was submitting for U.S. Green Building Council LEED certification. So, while the project was already largely designed and our LCA was coming late in the game, the LCA was useful for their future use. We did a proposed versus a baseline design, looking at what¡¯s there, how they designed their building versus some other options.

On a recent infrastructure project, we were asked to conduct an embodied carbon LCA, targeting a certification. We worked with the design team early and continually updated the embodied carbon results based on design changes. We provided guidance to the design team on the carbon hotpots in the project so they could explore alternates.

In this example, we identified concrete as a carbon hot spot. In both in-situ and precast form it was dominating the project¡¯s life cycle embodied carbon emissions. We first looked at optimizing the design to use less concrete. Then we specified lower carbon concrete mixes by coordinating with the local suppliers. As a result, this project used strategies such as reuse of existing site elements, an alternative design approach to reduce materials, different transportation options, specifying lower embodied carbon materials, and designing for extended service life. Employing those strategies, we managed to reduce embodied carbon by 54 percent.

Who needs a life cycle assessment?

The trend is toward governments and cities looking at life cycles of city-owned or federally owned buildings. Governments have large portfolios of buildings spread over the country and they want to know their carbon impact. They can lead the way.

From that point it will flow down to big players and developers. Any entity with a large portfolio of buildings should be studying this so they can understand their historic impact in terms of embodied carbon and move forward.

Yes, we need a life cycle assessment

When a client requests an LCA, our first step is to understand the need and the focus area for the evaluation. Some certifications (e.g., LEED) clearly define a focus on six impact categories. For others, the core focus might be on carbon footprint. A client might request an LCA for LEED, which is a clear process, or they might request something very broad.

But when a client approaches us about an LCA, they may want to understand emissions from the transportation angle or specific to products they¡¯re purchasing. Depending on their focus, they may not be interested in other life cycle stages.

Whole life carbon accounting

If you sum operational and embodied carbon, you get whole life carbon. As the name suggests, whole life carbon accounting focuses on life cycle carbon emissions.

This accounts for the embodied carbon (we use LCA to estimate/understand this aspect) and operational carbon (typically we employ energy modeling/utility analysis to estimate/understand it). In whole life carbon accounting, we seek the adoption of some form of recognized and standardized methodology to set consistent benchmarks and targets.

What drives requests for LCAs?

Requests for whole life cycle accounting are coming in from a broader sector of the economy. This includes buildings, infrastructure, water, mining, and power.

So, why do clients request an LCA?

• Certification: The client needs an LCA to attain a certification. This might be LEED or Envision.
• Local regulations: The city, state, or province requires an LCA apart from the energy modeling requirements for new developments.
• Internal mandates: The client¡¯s own ESG goals or a federal mandate require an LCA.

Stages of the life cycle

To understand carbon over the life of a building, we look at several different stages in a life cycle assessment: the product stage, transportation, the use phase, and the end-of-life phase. It is important for us to understand the client¡¯s focus and how they¡¯re using the life cycle assessment. What are they trying to understand about their emissions?

For transportation, we ask what sort of material is moving. What are the distances and intensities for the transportation modes? Are there any alternative modes available? We account for the emissions specific to transportation.

In the product stage, we look at material sourcing and extraction and manufacture. An LCA focus on that piece of the puzzle.

Life cycle assessments and steel

Concrete and steel typically dominate the embodied carbon picture of a building or an infrastructure project. The good news? Most of the steel produced in North America with electric arc furnaces uses high levels of recycled material; and renewable energy sources can potentially provide the power.

Many global steel and concrete producers now have their own decarbonization targets. They have started looking at manufacturing their products using clean energy sources where it is feasible. This is leading to products having significantly lower product-stage emissions.

Hence, we need to understand how materials and products are manufactured. It can have a big impact.

Hot spots and replacement cycles

Another embodied carbon hot spot? Insulation and glazing (glass). It will depend on how long these materials last and how frequently the owner needs to replace them over the building¡¯s service life.

You can leverage life cycle assessments to focus on materials life cycles as well. Some interior materials¡ªcarpets, flooring, or countertops¡ªmight not have a big impact when looked at initially. These interior elements might require higher replacement cycles, which can contribute to a large portion of embodied carbon over a 60-plus-year time horizon.

Most LCAs, however, exclude mechanical, electrical, and plumbing (MEP) equipment from their calculations. This is mostly due to lack of product specific environmental product declarations (EPD). EPDs help us identify their environmental impacts. As the industry is evolving, this is expected to change. MEP equipment evaluation is likely to become a key part of the LCA process. A building's concrete structure might last for 60 years but systems such as boilers and chillers have shorter service lives and need replacement every 15 to 25 years. Three replacement cycles over a 60-year period could potentially form a carbon hot spot for the project.

Performing life cycle assessments to holistically understand the carbon footprint is a step in the right direction for the building industry. And it puts our clients on the road to decarbonization.

Likewise, understanding the whole life carbon emissions of buildings is a key step for the industry. It can create meaningful reductions and credible pathways toward net zero. The solutions to meeting our climate change targets must be scalable, achievable, verifiable, and approached from a whole life cycle perspective.