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. The document aims to contribute to a more sustainable real estate industry and assist in achieving climate targets by offering guidance on developing net zero carbon buildings. The foreword is authored by Marc Lyon, the Head of Real Estate Development Switzerland at Implenia, underscoring the organization's commitment to sustainability in the construction sector.

Buildings are responsible for approximately 40% of global energy consumption and 36% of greenhouse gas emissions. Therefore, decarbonizing the building sector is vital for meeting climate goals. The concept of net zero carbon buildings focuses on minimizing operational emissions from energy use, reducing embodied emissions from materials, and offsetting any remaining emissions. Achieving this requires a comprehensive understanding of both operational and embodied carbon throughout the building's lifecycle.

Typically, net zero carbon buildings exhibit high energy efficiency and incorporate renewable energy systems, such as solar photovoltaics (PV). They also use a significant share of low-carbon construction materials and offset any residual emissions. Notably, most emissions arise from materials and construction, with upfront embodied carbon constituting about 70-75% of total lifecycle emissions.

Key strategies to achieve net zero carbon buildings include efficient design, the use of renewable energy, passive design techniques, low-carbon materials, and carbon offsets. It is essential to consider decarbonization from the early planning stages, beginning with site selection. Decisions regarding compact building design, orientation, and glazing significantly impact overall emissions.

Benchmarking is crucial for understanding a building's status regarding embodied and operational carbon. The whitepaper emphasizes the necessity for more ambitious targets to effectively reach net zero. A multifaceted approach is required to reduce carbon emissions throughout the entire lifecycle of a building, as no single solution will suffice.

Embodied carbon accounts for around 74% of a building's total lifecycle emissions, while operational carbon constitutes only 26%. This presents a significant opportunity for decarbonization through careful selection of materials and construction methods. The most effective levers for reducing carbon emissions lie in the early planning and design phases, focusing on site selection, access to renewable energy sources, and passive cooling potential.

On-site renewable energy generation, particularly through photovoltaics, is crucial for achieving net zero operational carbon. Factors such as orientation, tilt angle, and energy storage should be optimized for effective self-consumption of generated energy. Additionally, purchasing 100% renewable electricity is a strategy that further reduces operational carbon.

Natural shading, ventilation, thermal mass, and the use of green roofs and facades can passively decrease cooling loads and mitigate the urban heat island effect.

Implenia has set ambitious targets for its projects, aiming for net zero operational carbon by 2030 for new builds and by 2050 for refurbishments. The goal for net zero embodied carbon is set for 2040 for new constructions. Achieving these targets necessitates a combination of strategies across all lifecycle phases, from planning to operation.