Purpose There has been a growing interest in the environmental trade-off between renovation and reconstruction.Life cycle assessment (LCA) is a widely recognized method to quantify environmental impacts of buildings.However, the existing standards do not provide guidelines for defining the reference system period (RSP) and system boundaries (SB) to allow for a fair, robust and consistent comparison of renovation and reconstruction.Hence, this research establishes guidelines for defining the RSP and SB.Methods From literature, existing approaches are gathered for defining the RSP when comparing buildings with different service lives, and for defining the SB when an existing building is the starting point of an assessment.Eight criteria are then elaborated for defining the RSP and SB. For example, the RSP approach should differentiate between buildings from different construction periods, and the SB approach should be robust for time-related uncertainties. Therefore, the building's and building materials' service lives and replacement rates are varied; the standard deviation (σ) between the results then determines the robustness. Subsequently, the extent to which the approaches meet the predefined criteria is assessed. Finally, guidelines are established for defining the RSP and SB when comparing renovation with reconstruction.Results and discussion Three RSP approaches are selected: the RSP is equal to (i) the RSP of new building, (ii) the difference between the total service life of the building (TSLB) and the building age, or (iii) a service life extension. Furthermore, three SB approaches are selected: (i) the environmental impact is considered at the moment of production, (ii) the moment of occurrence, or (iii) is equally divided over different life cycles. As none of the SB approaches meet all predefined criteria, three partial allocation approaches are conceived based on a linear, concave and convex model. The concave model gives the most robust results (σ = 0.11), but is less consistent with the reality of emissions. The convex model is, in contrast, most consistent with the reality of emissions, but is less robust (σ = 0.16-0.19).Conclusions Based on the literature review and results, the authors recommend to define the RSP based on the difference between the TSLB and the building age for comparing renovation with reconstruction. For defining the SB in case of building materials that are retained over multiple life cycles, it is recommended to include the impact through a convex partial allocation model to compare the environmental impact of renovation and reconstruction in a robust and consistent way.
The European existing building stock contributes to 40% of the total energy use and 36% of the CO2 emissions. To deal with the climate crisis, European climate and energy objectives were defined. By 2050, CO2 emissions should be cut to 80-95% compared to 1990 and all buildings must be energy-neutral. The North-Sea Region alone consists of 22 million outdated dwellings built between 1950 and 1985 that are in high need of renovation. Nowadays, the renovation industry applies mainly manual on-site renovation techniques, resulting in a low renovation pace, relatively high labour costs and a long duration. To tackle the urgent need for rapid renovations, six countries of the North-Sea Region collaborate to upscale the current renovation process in the Interreg project INDU-ZERO “Industrialization of house renovations toward energy-neutral”. The project focuses on modular prefabricated renovation packages with fully integrated HVAC technologies to arrive at energy-neutral dwellings. The project researches the possibilities of far-reaching automated and industrialized production processes. A smart factory blueprint will be designed to speed up the renovation pace to a target of 15,000 renovation packages per year per factory while cutting the current price with 50%. This contribution focusses on three main topics: material use, operational energy use and transport. Firstly, the reasoning behind the renovation package design is explained. Next, the packages are adopted on an archetype dwelling to document the thermal performance before and after renovation. Finally, the associated logistics are studied. To summarize each individual research in a blanket result, the environmental impact is determined and compared to the non-renovated dwelling.
The European building stock is in high need of refurbishment due to its contribution to excessive global energy consumption. In the North-Sea Region (NSR) alone there are 22 million houses built between 1950 and 1985 with an annual CO2 emission of 79 Mton. Current deep retrofits are carried out on a limited-scale production, which may result in climate targets not being met in time. To tackle the need for rapid renovations, prefabricated insulation elements with integrated intelligent technologies, manufactured in novel smart factories using mass customization, could offer a solution. This approach is also followed by the Interreg project INDU-ZERO. The project examines a far-reaching automated production and develops a blueprint for a smart construction factory in the NSR that can produce 15 000 renovation packages per year. This paper aims to quantify the acceleration potential of the supply chain by improving its production, logistics, and on-site mounting processes for Dutch single-family terraced houses. First, the design of the renovation packages and smart construction factories are introduced. Then, the procedure is elaborated on how the supply chain can be abbreviated. The results show that the renovation cycle time can be completed within two weeks through coordinated efforts between production, logistics, and mounting.
The substantial contribution of buildings in the energy consumption and emissions renders the existing building stock a key element to tackle the climate crisis. Consequently, defining a deliberate decision-making process gains importance. Decisions are currently often based on building codes, budget, and in the best case Pareto optimality of the energy performance and the net present value of the life-cycle cost. The growing attention to sustainability, however, raises questions about the effect of environmental considerations on the outcome of the Pareto optimal solutions. This study quantifies the effect of including the environmental aspect as a third dimension to the current evaluation approach. Therefore, the most appropriate renovation measures are selected using a multidimensional Pareto optimization. The method is applied to a residential high-rise building in Belgium. Firstly, the Pareto front is constituted based on life-cycle costing and life-cycle assessment separately. Subsequently, the respective results are combined into an integrated life cycle approach by enumerating the LCA results as an external cost to the LCC results. The results show that the Pareto optimal solutions from a financial and environmental perspective do not coincide. Although the financial aspect dominates, adding the environmental cost eliminates low-performant financial optima, leading to optimal solutions with a larger insulation thickness.
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