Planning and development in urban areas is increasingly addressing sustainability and the natural environment. The initial planning and design phases dictate most of the emissions in a building or an infrastructure project. The planning of construction starts at the policy level, where objectives are set in terms of quantity, location, and general design. All have an impact on construction emissions. Infrastructure planning affects the transport of materials and the supply of clean energy for construction.
When a decision has been made about building a structure of a certain size and type, there are many options for minimising climate impact in the design phase. Material choice is often the most obvious means of reducing carbon emissions. Choosing bio-based construction materials over concrete and steel reduces emissions from material production, but also vastly changes the construction process and the emissions from transportation and on-site emissions.
2.1 Urban planning and infrastructure
Current trends in environmental urban planning primarily consider the biggest impacts, such as those from the in-use phase of the built area. The planning phase often dictates material choices and the repurposing of buildings, which affects construction emissions (Ameen, Mourshed, and Li 2015). Construction activities and the transport of building materials are, however, rarely mentioned. Considerations in the planning phase may pave the way for simple and cost-effective solutions that reduce emissions during construction. Decisions made during planning can greatly influence transportation and energy use, which are major factors in construction emissions. Such measures include using earth materials inside the local area to reduce the need for transportation and choosing construction methods, materials, and project locations that require less extensive groundwork or additional infrastructure. Such measures can reduce energy consumption, and thereby emissions, considerably.
Infrastructure for clean energy during construction and for effective waste management should also form part of urban planning. It is often not possible to charge battery-electric machinery and trucks on construction sites. Energy for heating is often needed and should be considered at an early stage in areas where district heating is available. Storage areas can be helpful for the better management of building materials and waste.
These are a few examples of how the planning phase can help reduce emissions. Further knowledge is needed about the influence of urban planning on emissions during construction.
2.2 Structural design and material choice
When designing low-emission buildings, the focus has traditionally been on energy efficiency and, more recently, building materials. The incorporation of reusability in design is now emerging. In the future, this has the potential to reduce construction waste and the need for virgin materials.
Design choices also have a considerable influence on carbon emissions during the construction phase. As with urban planning, cost-effective emission reductions can be achieved at this early stage of construction (Malmqvist et al. 2021; Zimmermann et al. 2021).
The use of prefabricated elements is one such method that can impact emissions from the construction process. Although less waste can be expected on the construction site, waste production may increase at the point of manufacture. Prefabricated elements are transported differently to raw materials, which also impacts emissions. Prefabricated elements are thought to improve the utilisation of materials and reduce waste compared to on-site manufacture (Hao et al. 2020). The reasoning is that the production site is better suited for the manufacture of the elements, and the personnel there are often more qualified to handle certain elements.
More studies are needed to assess the energy use of and waste production from the different construction methods and materials currently used. In this way, design choices can more easily be assessed with regard to construction emissions, rather than only considering emissions from material production and in-use energy emissions.