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Operational and Embodied Carbon of EWI

As the urgency to combat climate change intensifies, the construction industry is increasingly focused on reducing carbon emissions associated with buildings. Among the various strategies employed, External Wall Insulation (EWI) plays a pivotal role in enhancing energy efficiency and reducing operational carbon. However, it’s also crucial to consider the embodied carbon involved in the production and installation of EWI systems. This blog delves into the operational and embodied carbon aspects of EWI, underscoring its significance in achieving sustainable construction practices.

Why EWI?

External Wall Insulation is a method of improving the thermal performance of buildings by applying insulation to the exterior walls. This process significantly reduces heat loss, leading to lower energy consumption for heating and cooling, which is a win for both the occupant’s comfort and the environment. As buildings account for a substantial portion of carbon emissions globally, EWI plays a crucial role in the shift towards more sustainable construction practices.

What is operational carbon and how does EWI impact it?

Operational carbon refers to the carbon dioxide emitted during the building’s use phase, primarily due to heating, cooling, and lighting. EWI directly impacts this by enhancing the building envelope’s insulation properties, thus requiring less energy to maintain a comfortable indoor temperature. In climates with significant temperature variations, the savings in energy consumption—and by extension, carbon emissions—can be substantial over the building’s lifetime.

Enhanced energy efficiency

At its core, EWI works by wrapping the building in a thermal blanket, significantly reducing heat transfer through the walls. This reduction in heat loss during colder months and heat gain during warmer months means that buildings require less energy to maintain comfortable indoor temperatures. In practical terms, this translates to lower usage of heating and cooling systems, which are often powered by fossil fuels or electricity generated from carbon-intensive sources. By diminishing the demand for these systems, EWI directly contributes to a substantial reduction in the operational carbon emissions of a building.

Quantifying the impact

The impact of EWI on operational carbon can be quantified by examining energy consumption before and after its installation. Studies and real-world examples show that EWI can lead to energy savings of up to 50% in some cases, depending on the existing building fabric, the climate, and the type of heating and cooling systems in use. This reduction is not only beneficial for the environment but also results in significant cost savings for property owners over time.

Renewable energy

The benefits of EWI are further amplified when integrated with renewable energy sources. Buildings with EWI require less energy to heat and cool, which makes it more feasible to meet their reduced energy demand through renewable sources like solar panels or wind turbines. This synergy between EWI and renewable energy can lead to near-zero or even negative operational carbon buildings, where the building generates more energy than it consumes over a year.

Long-term sustainability

The reduction in operational carbon emissions through the use of EWI is a critical step towards achieving long-term sustainability goals in the construction sector. By lowering energy consumption, EWI not only reduces carbon emissions but also decreases the strain on the electrical grid and diminishes the need for energy production from fossil fuels. This contributes to a circular economy model, where buildings are designed and retrofitted to minimize environmental impact throughout their lifecycle.

Climate adaptation

Furthermore, EWI plays a vital role in adapting to climate change. As extreme weather events become more frequent and intense, the ability of buildings to maintain thermal comfort with minimal energy use becomes increasingly important. EWI enhances the resilience of buildings to temperature fluctuations, making them more comfortable and livable, even as the climate changes.

What is embodied carbon and how does EWI impact it?

While the benefits of EWI in reducing operational carbon are clear, the conversation around its embodied carbon is more complex. Embodied carbon encompasses all the CO2 emissions associated with the production, transportation, installation, maintenance, and disposal of building materials. For EWI, this includes the extraction of raw materials, manufacturing of insulation panels, and the installation process itself.

The type of material used for EWI plays a significant role in determining its embodied carbon. Materials like mineral wool, for instance, have different carbon footprints compared to synthetic options like expanded polystyrene (EPS). Additionally, the lifespan of the EWI system, its recyclability, and the energy used in its maintenance and eventual removal all contribute to its total embodied carbon.

Material production and manufacturing

The production and manufacturing processes of insulation materials for EWI are energy-intensive, contributing substantially to their embodied carbon. For instance, the production of mineral wool involves melting basaltic rock or recycled slag from steel plants at high temperatures, while manufacturing expanded polystyrene (EPS) requires the polymerisation of styrene monomers, a process that uses fossil fuels both as a feedstock and an energy source.

The carbon footprint of these materials can vary widely based on factors such as the energy source used in manufacturing (renewable vs. fossil fuel-based), the efficiency of the production process, and the distance materials need to travel to reach the construction site. Innovations in material science are aiming to reduce these impacts, for example, by developing bio-based insulators or improving manufacturing efficiency.


Transportation of materials from the point of manufacture to the construction site adds another layer to the embodied carbon of EWI. The distance travelled, mode of transportation, and weight of materials all influence the total emissions. Locally sourced materials or those manufactured using less carbon-intensive processes can significantly reduce the embodied carbon associated with transportation.

Installation process

The installation of EWI systems involves additional energy consumption and, consequently, carbon emissions. This includes the use of machinery or tools for applying the insulation and finishing materials to the building facade. While less significant than the production phase, the energy use and waste generated during installation still contribute to the embodied carbon of the system.

Maintenance, repair, and end of life

The life cycle of EWI systems does not end with installation. Maintenance and repair activities over the system’s lifespan, as well as the eventual removal and disposal of materials, contribute to its total embodied carbon. Some insulation materials may be recyclable, offering a potential reduction in embodied carbon by diverting waste from landfills and reducing the demand for new raw materials. However, the feasibility of recycling depends on the type of material and the availability of recycling facilities.

Strategies for reducing embodied carbon

Reducing the embodied carbon associated with EWI involves several strategies, including:

  • Material Selection: Opt for materials with lower embodied carbon, such as those made from recycled content or renewable resources.
  • Efficient Design: Designing EWI systems that minimize waste and are adaptable to future retrofitting or recycling efforts.
  • Lifecycle Assessment (LCA): Conducting comprehensive LCAs to understand the full environmental impact of EWI systems over their entire life cycle, enabling more informed choices.
  • Innovation and Research: Investing in new materials and technologies that reduce the carbon intensity of insulation products and their installation processes.
  • Policy and Regulation: Implementing regulations that encourage the use of low-carbon materials and practices in the construction industry.
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