Net zero - How to take the path to net zero carbon buildings

The whitepaper "Net Zero: How to take the path to net zero carbon buildings" was published by Implenia, a prominent international construction and real estate services provider based in Switzerland. This document aims to support a sustainable real estate industry and assist in meeting climate targets through guidance on developing net zero carbon buildings. The publication is overseen by Implenia's Real Estate Development division, with a foreword written by Marc Lyon, the Head of Real Estate Development Switzerland.

The intended audience for this whitepaper includes real estate developers, builders, architects, engineers, sustainability experts, policymakers, and all stakeholders involved in the real estate sector. By targeting these professionals, the whitepaper seeks to disseminate vital information regarding sustainable practices in building development.

Buildings are responsible for approximately 40% of global energy consumption and 36% of greenhouse gas emissions. Therefore, decarbonizing the building sector is essential for achieving climate goals. The concept of net zero carbon buildings is introduced, characterized by very low operational emissions from energy use, minimal embodied emissions from materials, and the use of offsets for any remaining emissions.

Net zero carbon buildings typically exhibit high energy efficiency and incorporate renewable energy systems, such as solar photovoltaics (PV). They also utilize a significant proportion of low-carbon construction materials. The paper emphasizes that most emissions originate from materials and construction (upfront embodied carbon), accounting for about 70-75% of total lifecycle emissions.

Several key strategies are outlined for achieving reduced carbon footprints in buildings. These include efficient design, renewable energy integration, passive design principles, low-carbon materials usage, and offsets. The importance of considering decarbonization early in the planning process is highlighted, especially during site selection. Decisions regarding compact building design, orientation, and glazing can significantly impact emissions.

The whitepaper discusses the role of benchmarks in assessing a building's embodied and operational carbon emissions. It advocates for more ambitious targets to reach net zero carbon status. The document stresses that a multifaceted approach is necessary to lower carbon emissions throughout the entire lifecycle of a building, as no single solution will suffice.

Embodied carbon constitutes around 74% of a building's total lifecycle emissions, while operational carbon accounts for only 26%. There is considerable potential for decarbonization through the careful selection of materials and construction methods to reduce embodied carbon.

The most effective levers for carbon reduction lie in the early planning and design stages. This includes considerations for site selection, renewable energy access, compactness, and passive cooling potential. The document emphasizes that compact building shapes lead to lower heating demand and reduced embodied carbon per square meter.

On-site renewable energy generation, particularly through photovoltaics, is essential for achieving net zero operational carbon. The orientation, tilt angle, and energy storage should be optimized for self-consumption. Additionally, procuring 100% renewable electricity can further diminish operational carbon, while green leases can secure renewable energy supplies.

The whitepaper also discusses passive strategies like natural shading, ventilation, thermal mass, and green roofs or facades. These techniques help to reduce cooling loads and mitigate the urban heat island effect.

Implenia has set specific targets for its projects: achieving net zero operational carbon by 2030 for new builds and by 2050 for refurbishments, with net zero embodied carbon targeted by 2040 for new constructions. A comprehensive strategy encompassing all lifecycle phases—from planning to operation—is deemed necessary to accomplish net zero carbon buildings. The earlier the focus on these strategies, the greater the potential impact.