Environmental evaluation of pareto optimal renovation strategies : a multidimensional life-cycle analysis

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

Upscaling the housing renovation market through far-reaching industrialization

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 The North-Sea Region alone consists of 22 million outdated dwellings built between 1950 and 1985 that are in high need of renovation.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 focuses 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 environmental impact of prefabricated renovation systems : a worthy alternative to on-site renovation?

The conventional renovation practices, which are mainly characterized by time-consuming manual on-site techniques, partly contribute to the low renovation rate. Accordingly, a faster and more efficient approach is necessary. The implementation of prefabricated systems could offer a possible solution. These systems are increasingly being studied, but little is known about their environmental impact. Hence, this study investigates the environmental impact by means of Life Cycle Assessment (LCA) of two prefabricated façade renovation systems being a timber frame and a sandwich panel; and compares it to a well-known on-site technique, External Thermal Insulation Composite System (ETICS). First, reference designs are assembled. Subsequently, the impact of different life cycle stages is determined in order to clearly indicate differences between on-site and prefabricated systems. More specifically, the production, transport, replacement and end-of-life stage are assessed. In the end, the environmental impact is examined over time combining all stages. The results show that the prefabricated systems are not yet a worthy ecological opponent to ETICS. As of the production stage, the environmental impact appears to be higher. Optimising the reference systems through an extensive redesign could lead to more competitive or even favourable results in terms of environmental impact

Renovate in One Step, Stepwise, or Reconstruct?

The existing building stock is outdated, consumes a lot of energy, and is a major contributor to the global greenhouse gas emissions. Consequently, there is an urgent need for a transition of the existing building stock towards energy and carbon neutral buildings. There are three main pathways that could facilitate this transition: one-step deep energy renovation, step-by-step deep energy renovation, and demolition followed by new build. The importance of a sustainable transition, however, raises the question of how the environmental impact and financial cost of these three main pathways relate for different types of single-family dwellings. Several researchers have already searched for decision-making methods that integrate Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) to assess both environmental impacts and financial costs. However, a systematic comparison of the three pathways is lacking. Moreover, existing standards on how to perform an LCA are very conceptual and too vague to allow for a fair and consistent comparison of the three main pathways. This leaves a lot of freedom to LCA practitioners to make assumptions, implement simplifications and set their own boundary conditions. This can contribute to variations and contradictions in the trade-off between the pathways. This research project, therefore, aims to develop a well-defined and robust methodological LCA framework to compare the three main pathways in a fair and consistent way, provide insight into which pathways are most optimal for different types of single-family dwellings, and determine tipping points in the trade-off between the pathways to define more tangible and general building renovation guidelines

Analysis of potential impacts of policy options for inspections of stand-alone ventilation systems in EU dwellings

Various field studies have shown that in a vast majority of European countries the quality of installed residential ventilation systems is poor, with a large proportion of systems having significantly lower installed flow rates than the required values, or having poor energy performance due to flaws in design, installation or operation. This paper analyses the potential impact of different policy options for an EU-level approach for inspection of stand-alone ventilation systems in residential buildings until 2050. The analysis accounts for different scenarios based on the evolution of the EU dwelling stock, the evolution of the market share of ventilation systems in buildings, and the impact of policy options for inspection on the ventilation related energy use and indoor air quality in dwellings equipped with various types of ventilation systems. This analysis is part of a technical study contracted by the Directorate-General for Energy of the European Commission to a consortium formed by INIVE and BPIE, whose aim was to provide technical support on the possibilities and timeline for introducing inspection of stand-alone ventilation systems in buildings, linked to Article 19a of Directive 2018/844, which requires that the Commission must carry out a feasibility study on this topic. The paper discusses the methodology and results of the impact analysis calculations. The calculations of ventilation related energy indicators and carbon emissions are based on the principles of the ecodesign SEC-calculation method (Directive 2009/125/EC). The IAQ-indicator is based on the assessment of a generic pollutant dose taking account of the effective flow rates and exposure times in the different types of ventilation systems. The results show that inspection options contribute to a smaller or larger extent to a better indoor air quality, at the same time increasing the ventilation related energy use. It is not evident to rank the various policy options in terms of preferences: they could be implemented consecutively, by looking at societal support in case of a mandatory implementation

Effect of a one-dimensional approach in LCA on the environmental life cycle impact of buildings : multi-family case study in Flanders

The environmental impact of buildings is commonly quantified through life cycle assessment (LCA). Because of practical constraints (e.g. data limitations, timing, complexity), various simplifications are often made. However, the impact of certain simplifications is not clear. Due to the particular geometry of a building, the execution of renovation measures typically entails environmental impacts due to material and energy use at building envelope interfaces which are not considered in simplified LCAs. Hence, this paper examines the effect of a one-dimensional approach as simplification strategy on the environmental impact regarding material use and operational energy use for different renovation scenarios applied to a residential high-rise building. A simplified LCA is therefore compared with a detailed LCA that considers the real building design. First, the effect of linearly scaling the environmental impact based on a one square meter approach is confronted with the real building complexity. Then, the impact of neglecting thermal bridges on the operational energy use is analysed. Finally, both results are combined to evaluate the overall effect on the environmental life cycle impact. The simplifications entail an underestimation of the environmental material use, operational energy use and life cycle impact of 6–49%, 10–36% and 10–30%, respectively. The underestimation of the life cycle impact highly correlates with the operational energy use because of the significant contribution of the operational energy use to the environmental life cycle impact, namely 81–99%. As a result, the effect of simplifications concerning material use on the total life cycle impact is found to be negligible

The environmental impact of one-step deep renovation, reconstruction and step-by-step renovation: single-family case study in Flanders

A sustainable transition of the existing dwelling stock towards carbon neutrality is a key element in tackling the climate crisis. To facilitate this transition, one-step deep renovation, demolition followed by new build (i.e., reconstruction) and step-by-step renovation are possible pathways. The choice between these three pathways will depend on many aspects, but how does their environmental impact relate? Lowering the operational energy use is a first essential step, but the environmental impact related to the material use can become equally or even more important in case of low-energy buildings. Today, a systematic comparison of these three pathways from an environmental life cycle perspective is missing in the state-of-the-art. Hence, this paper compares the environmental impact of one-step deep renovation, reconstruction and step-by-step renovation with the conservation of an uninsulated single-family dwelling. The environmental impact is calculated by means of a Life Cycle Assessment (LCA) over a 60-year study period following a cradle-to-grave approach. For each pathway, identical strategies for the different building envelope components and technical installations are assumed. For step-by-step renovation, six steps in two sequences are considered, corresponding to the highest and lowest resulting environmental impact. The results show that one-step deep renovation has the lowest environmental impact, followed by reconstruction. Their environmental impact is respectively 73% and 68.5% lower than conservation. Step-by-step renovation has a higher impact than both one-step deep renovation (+26% to +73%) and reconstruction (+7% to +48%), but the impact is still 53% to 66% lower than conservation, depending on the sequence of the measures

Renovate in one step, stepwise, or reconstruct?

The existing building stock is outdated, consumes a lot of energy, and is a major contributor to the global greenhouse gas emissions. Consequently, there is an urgent need for a transition of the existing building stock towards energy and carbon neutral buildings. There are three main pathways that could facilitate this transition: one-step deep energy renovation, step-by-step deep energy renovation, and demolition followed by new build. The importance of a sustainable transition, however, raises the question of how the environmental impact and financial cost of these three main pathways relate for different types of single-family dwellings. Several researchers have already searched for decision-making methods that integrate Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) to assess both environmental impacts and financial costs. However, a systematic comparison of the three pathways is lacking. Moreover, existing standards on how to perform an LCA are very conceptual and too vague to allow for a fair and consistent comparison of the three main pathways. This leaves a lot of freedom to LCA practitioners to make assumptions, implement simplifications and set their own boundary conditions. This can contribute to variations and contradictions in the trade-off between the pathways. This research project, therefore, aims to develop a well-defined and robust methodological LCA framework to compare the three main pathways in a fair and consistent way, provide insight into which pathways are most optimal for different types of single-family dwellings, and determine tipping points in the trade-off between the pathways to define more tangible and general building renovation guidelines