The environmental impact of the construction sector is the result of countless processes in the stages of the building life cycle. Material processing and energy use are key factors and sometimes interrelated. The transport of materials and on-site energy use and waste are prominent environmental impacts during construction. Efforts to reduce greenhouse gas emissions from construction must be based on measurements and estimates. Measures to reduce emissions in the construction phase may have an impact on other phases, such as material extraction and processing. Life cycle assessment (LCA) has become the favoured tool in the industry. It systematically estimates the environmental impacts of the different phases in the construction of a building. LCA relies on the measurement of real processes and a systematic collection of such data.
3.1. Harmonised LCA data and methods
LCA is established in the construction industry as a tool for estimating environmental impacts, including global warming impact. The methodology and standards are also used as a basis for the forthcoming limit values for emissions in construction in the Nordic countries and measurements of actual emission values from construction (Nordic Innovation 2023).
The outcome of an LCA can reveal the impact of various building elements and life cycle stages within a typical reference study period, usually spanning 50 years. In the upcoming regulation on climate declarations in the Nordics, LCA will be used for the calculation and declaration of climate emissions in new construction and will be used to document that limit values have not been exceeded where these are introduced (Nordic Innovation 2023). Since 2018, Nordic building authorities have been discussing climate emission regulations and pursuing harmonised LCA methods for buildings. The concept of LCA for evaluating the total carbon emissions of buildings is gaining traction in the Nordic countries and Estonia. The EU is also planning similar legislation. As LCAs and climate declarations are new, the Nordic countries have the opportunity to align and share their practices in this evolving field. (Nordic Innovation 2023). It is beneficial for the Nordic countries to align their LCA content, and also crucial to track and keep pace with developments in Europe and beyond.
By aligning methods and rules in the Nordic countries, construction firms will be able to offer low-carbon solutions and expand their markets beyond national borders. This will also assist policymakers in supporting each other’s climate goals in regulations, procurement, and policy development.
In 2022 and 2023, the building authorities of the Nordic countries and Estonia published a roadmap - Harmonising Nordic Building Regulations Concerning Climate Emissions. Although the roadmap spans the period 2023 to 2030, the joint funding from the Nordic Sustainable Construction Programme is only until the end of 2024. It would be beneficial to establish a follow-up programme to sustain efforts in sustainable construction.
3.2 Estimation of emissions from construction
Emissions from the construction process were, until recently, regarded as less important than operational emissions. There are still gaps in knowledge regarding the amount of emissions, both at the building level and accumulated at the regional level (Kanafani et al. 2023).
There is a limited number of studies about construction phase emissions at the building level. Furthermore, buildings vary widely in their size and construction.
Emissions from construction at the national level are also an important metric. Reductions at the building level may be outweighed by the increase in the number of new buildings and built areas, as is further discussed in Chapter 7 about sustainability.
The roadmap mentioned in the previous chapter collates the life cycle modules that the Nordic countries are including. Only Norway and Sweden have already implemented or will implement modules A4 and A5. Denmark, Estonia, Finland, and Iceland have proposed to include A4 and A5 in the scope of their future regulations. The reason for them not being included now is partly due to a lack of data. We need to collect more data on emission figures for parts A4 and A5 to be able to set a limit value for these modules. The development of default values for modules A4 and A5 would benefit the process for designers (Frischknecht et al. 2023).
A recently published study presents an analysis of the carbon emissions of 61 Danish construction sites based on their energy consumption, waste production (module A5), and transport to the site (module A4). It also collates existing studies on carbon emissions in modules A4 and A5. The analysis states that only a few studies investigate emissions generated from transporting materials to sites or from construction site processes. This demonstrates the need for a major case study covering multiple cases in order to improve knowledge on emissions related to these modules (Kanafani et al. 2023).
The transportation of building materials should be considered a part of the construction process and the environmental impact attributed to that phase. Measuring and estimating carbon emissions from transportation is, however, challenging as data is often missing and the boundary is difficult to define. The current machine fleet needs to be analysed, while current emissions and fuel consumption need to be estimated, as does the distribution of emissions according to the type and size of machinery. This could all help in the design of policies and other measures.
In terms of waste from construction, the amount of materials that become waste during new construction is often underestimated (Fufa et al. 2023). Here, generic estimations of typical waste ratios of different building materials during the construction phase would be helpful in the LCA process.