Design is most important issue in determining GHG emissions

Design is the most important factor in determining greenhouse gas (GHG) emissions over a building’s lifetime and by the time the construction process begins, the majority of decisions affecting the project’s GHG emissions are locked in.

That is one of the key messages from McKinsey's Seizing the decarbonization opportunity in construction report, which stresses the ability to influence a building’s lifetime emissions is highest very early in a project and before construction has started.

Fundamental design decisions, such as new construction versus upgrading, building size and shape, level of insulation, and floor-space flexibility, can have a significant impact on emissions for decades to come. If left unaddressed, the construction ecosystem’s carbon output is expected to grow over the next 30 years as we seek to meet the demands of an expanding population and increased urbanisation.

On a positive note, this opens opportunities to optimise new builds, while a simultaneous shift toward renewable energy will help to mitigate emissions. New build construction is responsible for more than 2.5 gigatons of CO₂e globally (5 percent of total GHG emissions) and the smart-buildings segment is expected to grow at 10-13 percent CAGR until 2025.

With power-system decarbonization leading to a reduction in emissions by 2050, the need to eliminate annual emissions remains significant for the construction and real estate ecosystem to meet the 2016 Paris Agreement’s 1.5-degree warming target.

GHG emissions from the construction ecosystem are mainly driven by two components: raw-material processing for buildings and infrastructure (about 30 percent of total construction emissions per year, largely cement and steel) and buildings operations (about 70 percent), the report notes.

The contribution from raw materials comes primarily from energy-intensive cement production and through metals (about 50 percent of global steel production is used for construction), which contributes almost 7 percent of global GHG emissions. The contribution from commercial and residential building operations is mainly driven by space and water heating within buildings, heat leakage due to poor insulation, and other energy usage such as lighting, air conditioning, and appliances.

The report states decarbonization of materials can be achieved through a combination of several main measures:

• Demand reduction and circularity Lowering demand for primary resources through design and process optimization (including reduced waste, improved building footprints, and limited overspecifications), and by increasing closed-loop circularity for materials and components (including increased usage of scrap material and reduced recycling-yield losses). Using generative design to create outcome-based designs that help frame and clarify how different materials and design choices can lower GHG emissions
• Optimizing construction and material Shifting commonly used materials and equip­ment to alternatives that are more energy efficient, including substitution by low-carbon materials, higher-performing materials, and electrification of heavy equipment. Pushing toward productization of projects, modular­i­zation, and off-site construction to reduce the overall footprint of the construction process
• Material decarbonization Reducing emissions during production of required materials, including increased production efficiencies, electrification of processing equip­ment, and technology advancements

The pathway for this vision of net-zero carbon buildings at zero cost increase may require a rethink­ing of basic principles and a combination of existing and alternative materials, it adds.

In conclusion, the construction industry is experiencing multiple disruptions, but the drive to sustainability is racing ahead. "Change is arriving quickly, and we are already seeing many modifications to new and existing projects. Accelerating this journey and addressing the challenge head-on will be key."