Net Zero Resource Hub
Section 2: Early carbon optimization
Need for early carbon optimization
Optimizing carbon in various project stagesConducting 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||
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 carbonThe 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 potentialCost 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
|GLA London Plan||
Living building challenge
Table 2.Certification schemes, and regulations that promote early design (either directly or indirectly)