Circular economy in the Swedish building sector: Investigating options for old windows

University essay from Lunds universitet/Energi och ByggnadsDesign; Lunds universitet/Institutionen för arkitektur och byggd miljö

Abstract: The construction industry is expected to generate 2.2 billion tons of waste by the year 2025 and was responsible for 39 % of GHG emissions generated by the building processes and energy consumption, in 2017. In 2018, the Swedish construction industry accounted for 21 % of the total GHG emissions (including imported emissions) and 35 % of the total amount of waste in the country. In these past decades, the industry has mainly focused on reducing energy use during a building’s operational phase but have neglected to put as much focus on the embodied energy. In order to build sustainable cities, it will be a necessity to discuss and implement circular flows within architecture and construction to reduce the embodied energy as well. Not many regulations regarding circular economy have been implemented at an EU level as of today, leaving room for innovative and free concept interpretations. The EU has presented a new Circular Economy Action Plan as part of the European Green Deal, an agenda for sustainable growth. The new action plan aims at reducing pressure on natural resources and creating sustainable growth and jobs, by including and targeting all phases of a product’s lifecycle. This should be achieved by focusing on sectors that use the most resources and have a high potential for including circularity, such as the construction industry. While some building materials, such as bricks or roof tiles, have been implemented further in circular methods of waste management, windows have not. Most window replacements during renovation end up as waste, and not many windows are being reused or recycled. An issue with circularity is that there is not much information on the subject of reuse and recycling of windows in Sweden, meaning that there are not many professionals with this area of expertise, which in turn leads to a lack of information on the economic benefits, opportunities, and ways to improve the potential methods. Since reuse of building products is not common praxis yet, several other difficulties and issues need to be solved. These difficulties include storage, Swedish building regulations (BBR), knowledge gaps, government procurement etc. The Swedish building regulations are also regulating what criteria certain components of the building envelope must fulfil to be approved, e.g., requirements for U-values and energy use. This degree project presents a study of managing the existing windows of a building complex in Lund, Sweden, where five residential buildings are planned to be demolished in order to later be re-built on the same property. As part of a research project within the programme Spara & Bevara, funded by the Swedish Energy Agency, this report focuses on analysing the options of reuse, recycling, or disposal of the existing windows. The options will be investigated by environmental impact and cost. The results will be conducted through a literature review, interviews, energy simulations, lifecycle assessment (LCA) and lifecycle cost (LCC). A simple SWOT-analysis was conducted to investigate what strengths, weaknesses, opportunities and threats may occur when recycling or reusing existing windows. A thorough review of research papers, articles, and books was carried out to explain the present situation, the possibilities, and the issues that are associated with the subject. The literature review, combined with interviews and events, provided enough input data and information to make it possible to conduct simulations and calculations, as well as assign realistic cases of reuse/recycling of windows for the project. A site visit was also conducted in the neighbourhood where the buildings are located in order to take thermal images of the existing windows. Besides the thermal imaging, a quick physical inspection of the windows was made to see what conditions they were in and what factors to include in the calculations. Five cases were investigated, whereas two cases investigated the option of refurbishing the windows and three cases included exchanging them for new ones. The results from the energy simulations concluded that none of the improved cases fulfil the criteria of BBR, which is that the energy use should be less than 75 kWh/m2. If the goal of renovating the building is to get a lower value than the criteria, more options for refurbishment have to be investigated and applied to this study. BBR also sets a maximum U-value for windows of 1.2 W/m2K which is not fulfilled for the renovated windows, but could be possible to deviate from if the exception is because of reduced climate impact due to reuse of products. Given that the existing windows are in good shape, based on the analysis of the images from the thermal imaging camera, it could be considered beneficial to argue for renovation rather than demolition of the building product. Refurbishing the windows, rather than exchanging them, resulted in the best economic outcome. Where refurbishing the windows becomes profitable after only ten years, and exchanging them does not become profitable for at least 30 years. The LCC calculations mostly depend on input values, hence the interest rate and energy price growth should be carefully considered. Different interest rates and price growth rates were investigated, where a higher energy price results in a shorter pay off time. On the contrary, higher interest rates result in higher economic losses. In the same way, refurbishing the windows is more preferrable from an LCA viewpoint, where recycling glass and using existing windows harms the environment less than producing new windows, even if the old windows were to be reused in the building. A few conclusions from this study indicates the following: - The market for recycling flat glass in Sweden needs to be developed. - Reusing windows reduces waste residues but does not necessarily result in the lowest amount of released emission. - The biggest limitation for reusing or recycling windows is the immature/undeveloped business market, along with responsibility and warranty issues. - The best alternatives for managing windows of the building complex in Lund is either replacing the interior windowpane with an energy glass, or replacing the interior windowpane with an insulating cassette.

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