Net Zero Resource Hub

Section 2: Early carbon optimization

Need for early carbon optimization

Optimizing carbon in various project stages

Conducting Life Cycle Assessment (LCA) helps to measure and reduce the environmental impacts of your building, achieve green building certifications, and comply with regulations. Depending on the objective, LCA can be performed during multiple stages of a project and can provide various advantages (refer to Table 1).

Project stage	Advantages of performing building LCA
Site selection stage	Calculate influence of the site on carbon footprint (to calculate the foundation type required, soil stabilization requirements, etc)
Concept stage	Obtain baseline (for LEED and other certification purposes, to measure reduction against baseline) Set embodied carbon and whole-life carbon goals/targets
Technical stage	Explore material efficiency Check for sustainable alternatives Perform structural LCA, architectural LCA, services LCA Achieve certification
Specification stage	Choose materials by EPDs Responsible sourcing Material efficiency
Post-construction	Tracking of carbon

Table 1. Advantages of performing LCA during various project stages

LCA can be performed at multiple stages but if your goal is to achieve maximum embodied carbon reduction, you need to perform it when you have the maximum power to influence design and specification choices.

Strategies to reduce embodied carbon

The Carbon Neutral Cities Alliance (CNCA) has identified five different tactics that can be deployed to reduce carbon emissions(see Fig 1).

Redefine the solution: finding alternative ways to reduce carbon. For example, if a leisure time facility is underused, the problem may relate to public transport access as opposed to needing to rebuild or renovate the building.
Refurbish existing assets: This reduces total materials use and can be a powerful decarbonisation strategy where it does not compromise energy efficiency. For example, renovations to increase usage efficiency in capacity, occupancy, or both.
Reduce and Replace materials and structures by design and use lower carbon structures and materials where appropriate.
Reuse products and materials, at end of life for additional uses for unused products from sites and for salvaged materials from refurbishments and demolitions
Require low carbon products, for example specifying low carbon products while limiting and/or substituting the use of high carbon materials for lower impact ones.

Fig 1. Embodied carbon reduction potential

During the early design stages, there is greater flexibility to influence all of the steps to reduce embodied carbon. During this stage, design teams have the capability to assess different solutions, structural frames, locations, material choices, and many more.

Identifying the stage with the highest potential

Cost considerations

Fig 2. Cost vs. Carbon during project stages

Cost becomes a significant limiting factor as the project moves forward in time (see Fig. 2). For example, in the pre-construction phase, when materials have already been specified and orders have been placed, allocating an extra budget for procuring low-carbon materials is not a feasible option and will affect the sustainability outcome of the project. Even from a business perspective, incorporating LCAs as early as possible allows designers to differentiate tenders by providing an extra offering.

Design considerations Certain design elements are better addressed early in the design process. Once these are fixed, it may result in additional costs to re-address it at a later stage. For this reason, it is recommended to integrate LCA as early as possible in the design process. For example, is more appropriate for early stages than product procurement for example looking at the structural frame, foundation, and slab options. If you change your mind later, you will need to redesign the entire thing which results in extra costs.

Certification schemes and regulations that

promote early carbon optimization

Schemes	Description
GLA London Plan	Requires the Whole Life Carbon (WLC) Assessment to be performed in three stages including pre-application and planning submission stage. The Planning submission stage is the most critical stage, as it can affect whether or not planning is approved.
Living building challenge	Requires that the embodied carbon emissions from the foundation, structure, and enclosure have been reduced by a minimum of 10%, compared to the baseline scenario. The total embodied carbon emissions of the project must not exceed 500 kg-CO₂e/m². If you want to meet these targets, then measuring your project’s embodied carbon at an early stage is critical.
LEED	In LEED certification, credits are offered based on the percentage reduction from the baseline. Though there is no requirement for early carbon optimization as such, it will be tough to meet the maximum credits if you do not optimize embodied carbon during the early phase.