Understanding the Life Cycle Stages in Construction

A building is not just a collection of materials, nor is it simply the sum of its parts. It is a story, one that spans from the moment raw materials are extracted from the earth, all the way through its operational life, and eventually to its deconstruction. This story, when measured, reveals the full environmental cost of constructing and inhabiting buildings. Life Cycle Assessment (LCA) offers a methodology for this, breaking it into stages that allow us to see the bigger picture, providing invaluable insight for architects, engineers, and stakeholders.

What is Life Cycle Assessment in the Built Environment?

Life Cycle Assessment (LCA) is a method used to measure and evaluate the environmental impacts associated with all stages of a product's life. This could be applied to anything from a paper clip to a building.

In construction and architecture, LCA is typically applied to materials, systems, and entire buildings. It helps us understand not just the impact of one product, but how all elements of a project contribute to environmental performance.

To get accurate assessments, we break the life cycle into stages, referred to as modules. These are outlined in standards like EN 15978 and ISO 14040/44. The modulars are structured to tell a story of the materials life. Below is a breakdown of all the modules with LCA.

Module A1 - Raw Material Supply

The journey of a building begins far before any designs are drawn or construction equipment arrives on site. It starts with raw material extraction, a critical first stage in the life cycle. Timber is felled in the dense forests of the Central North Island, steel is mined from the rich iron ore deposits in Western Australia, and clay is extracted to make bricks. Each of these materials carries a hidden environmental cost. The energy used to extract and refine these resources, often from remote areas, contributes to emissions long before the building takes shape.

Take timber, for example, the environmental cost is not limited to the cutting of trees but extends to the impact of logging practices, land degradation, and potential biodiversity loss. Understanding this initial stage allows us to choose materials wisely, considering the long-term effects of their extraction.

Module A2 - Transport to Manufacturing

Once the raw materials are extracted, they are transported to manufacturing plants where they are processed into usable products. This stage, transport to manufacturing, includes the emissions produced by trucks, ships, or trains moving materials from quarries or forests to factories. Whether it is the shipping of steel beams to a fabrication yard in Christchurch or the trucking of timber to a mill, transport emissions can be significant, especially when the materials travel long distances.

In the case of timber, for instance, the transportation of felled timber from forests, often shipped overseas for processing into products, can add substantial emissions. Even though timber is a common material, the distance it travels and the energy-intensive processes it undergoes make the journey from A1 raw material supply to A3 manufacturing a key consideration in any LCA.

Module A3 - Manufacturing

This is the stage where materials are transformed into finished products. Here, raw materials are crafted into elements like steel beams, concrete slabs, or insulation. Each of these processes requires energy, and with energy comes emissions. Manufacturing, especially energy-intensive processes like cement production or steel fabrication, contributes heavily to a building’s embodied carbon. This is why it is important to know what type of energy is being used, as the difference between renewable energy and fossil fuel energy can vary significantly.

For example, structural steel manufactured in Singapore using an electric arc furnace is not the same as steel made in other regions, due to the differences in energy sources. The emissions from this production are considerable. While the manufacturing stage is essential for creating the materials that make up the building, it is also one of the most energy-consuming stages, making it vital to assess closely during LCA.

Module A4 - Transport to Site

Once materials are manufactured, they must be transported to the construction site. Whether by truck, rail, or barge, this stage involves the movement of the materials to the project’s location. For construction projects in New Zealand, such as residential buildings on Waiheke Island, this stage may involve transporting prefabricated panels or concrete from the mainland by ferry.

The environmental impacts here can vary significantly based on the transport distance, the weight of the materials, and the method of transport used. Long-distance shipping or transport by heavy-duty trucks can significantly increase carbon emissions, making it important to consider the proximity of suppliers and materials to the construction site whenever possible.

Module A5 - Construction and Installation

This stage represents the assembly of the building itself. It involves the installation of all materials, from structural steel and cladding to electrical systems and fixtures. It is here that we see the culmination of previous stages, but also where additional emissions are introduced due to the construction process. Not all materials are installed the same way, produce the same amount of waste, or require the same resources to be installed. Large machinery, generators, cranes, and other equipment are often used, as well as waste collection, all of which generate emissions.

In urban areas, such as the CBD of Sydney, this stage is further complicated by the need for heavy machinery to work in constrained spaces, increasing both the emissions from construction equipment and the environmental disruption. But it is not just the machinery that contributes to emissions, on-site activities also include waste, such as scrap materials, packaging, and offcuts left over from construction. Minimising this waste through good site management is crucial.

Module B1 - Use

Once the building is complete, it enters its operational phase. B1 is the stage where the building is used and inhabited. This phase evaluates the direct environmental impacts arising from a building's use, primarily capturing emissions from building materials, physical degradation, and HVAC refrigerant leakage, which can contribute to greenhouse gas emissions. Despite its importance, the B1 stage is often overlooked in LCA assessments.

In the New Zealand context, a timber-framed house in Auckland might release volatile organic compounds (VOCs) from treated wood during its operational phase. Additionally, a commercial building in Melbourne would have refrigerant leakage from HVAC systems, which are essential for maintaining indoor comfort in Australia’s varying climate.

Module B2 - Maintenance

Over time, buildings require maintenance to preserve their function and aesthetics. B2 includes the regular upkeep of a building, from replacing worn-out fixtures to resealing windows. A simple example might be the repainting of a commercial building’s exterior in Melbourne to protect it from the coastal weather. Although these tasks are relatively minor, they contribute to the ongoing environmental impacts.

In New Zealand’s more temperate zones, frequent maintenance is often needed for wooden buildings due to the moisture in the air. This results in more frequent repainting or resealing, which carries its own emissions from the materials and energy used during maintenance.

Module B3 - Repair

When a building experiences damage, whether from a storm, wear and tear, or an unforeseen event, repairs are necessary. B3 covers the work required to restore the building to its original condition. This may include replacing a broken window or patching cracks in the concrete. The materials required for repair, such as glass, timber, or concrete, must be sourced and transported, generating emissions that must be accounted for in LCA.

An example of the B3 stage in the Life Cycle Assessment framework could involve fixing a damaged roof in New Zealand. For instance, after a storm in Auckland, repairs might be needed to replace broken tiles or patch leaks. The environmental impacts assessed under B3 would include the production and transportation of replacement materials, the energy used during the repair process, and the disposal of damaged components.

Module B4 - Replacement

Over the life of a building, certain components will inevitably need to be replaced. B4 captures the impact of these replacements, which can be significant. Examples include replacing carpeting or changing roof membranes. These materials are often replaced at set intervals, for example, carpets every 10 to 15 years, roofing membranes every 20 to 30 years, which means the emissions associated with these replacements must be carefully considered.

For an office space, carpet might be replaced every 5 years for new tenants, each covering a new A1 to A5 impact for replacement. As a result, it is important to consider materials that are long-lasting and are unlikely to be replaced during the building’s life span.

Module B5 - Refurbishment

Occasionally, buildings are reimagined and redesigned. B5 refers to the process of major refurbishment, when parts of the building are restructured or repurposed entirely. B5 involves more substantial changes aimed at improving or modernising the building, such as upgrading finishes or systems. It assesses the impacts of modifying existing materials rather than replacing them entirely.

For example, in a commercial building in Auckland undergoing refurbishment, an assumption might be that the existing concrete flooring will be polished and resealed rather than replaced. The LCA would assess the environmental impacts of the polishing process, such as the energy used by machinery, the emissions from sealants, and the disposal of any waste generated during the process.

Module B6 - Operational Energy Use

Energy use continues to be an important factor throughout the building’s life. B6 refers to the energy consumed by the building during its operational phase. This includes the energy required for lighting, heating, cooling, and powering equipment. For example, in a high-rise office building in Sydney, energy is needed for elevators, ventilation, and lighting systems. In New Zealand, the grid is largely powered by hydroelectric and geothermal energy, which helps lower the carbon footprint of energy use. However, buildings in Australia may rely more on fossil fuels, making operational energy use a significant contributor to carbon emissions.

How the building is designed, whether it includes passive design features or energy-efficient systems, plays a significant role in its overall emissions. Buildings that incorporate energy-efficient systems, such as geothermal heating or solar panels, help reduce the carbon intensity of this stage.

Module B7 - Operational Water Use

Water use in buildings may not always be included in LCA, but it is crucial in some instances. B7 includes the energy required to heat and move water through a building. For instance, in Auckland, a hotel or apartment complex might use water for cooling towers in HVAC systems, irrigation for landscaping, and daily activities like restroom facilities. The environmental impacts assessed under B7 would include the sourcing, treatment, and disposal of water, as well as any associated emissions or energy use.

Module C1 - Deconstruction

Eventually, a building will be dismantled. C1 is the stage where the structure is taken apart and materials are removed from the site. Deconstruction can either be a careful process of salvaging materials for reuse or a more straightforward demolition that sends everything to landfill. In New Zealand, there is a growing trend to deconstruct buildings with the aim of reclaiming materials like timber or steel, reducing the need for new resources.

Module C2 - Transport of Waste

As materials are removed, they need to be transported away from the site. The emissions from this transport must be considered, whether the waste goes to a recycling facility, landfill, or a new project site.

Module C3 - Waste Processing

Once materials are transported, they are sorted, cleaned, and prepared for reuse or recycling. Materials like metals, glass, and timber are often recovered and repurposed. Efficient waste processing can help offset the need for new materials in the future.

Module C4 - Disposal

Unfortunately, not all waste can be reused or recycled. C4 includes the emissions associated with sending waste to landfill or incineration. These processes contribute directly to a building’s end-of-life emissions and can significantly affect its total carbon footprint.

Module D - Beyond the System Boundary

Finally, Module D accounts for any benefits that come from materials or energy recovered at the end of a building’s life. This is often referred to as the circular stage, when recycled steel is used in new construction, or when demolition waste is used as aggregate in road bases. These savings are not part of the building’s direct footprint, but they are credited for reducing future impacts in other systems.

Understanding the life cycle stages of a building is essential for evaluating its environmental impacts. By breaking down each phase from resource extraction through to disposal, we gain a clearer view of the materials and processes that shape the built environment. This structured approach allows us to identify where the greatest impacts lie and to make more informed decisions at every stage of a project. From architects to engineers to policymakers, everyone in the construction ecosystem can benefit from integrating life cycle thinking into practice.

For those wanting to dive deeper, we recommend exploring our other articles on Biogenic Carbon Storage and Life Cycle Assessment scopes, which provide valuable context and clarity around how different carbon sources and assessment boundaries influence LCA results. To learn more, refer to our detailed article: Understanding Key LCA Terminologies: A Guide for Built Environment Professionals