Explorative life-cycle assessment of renovating existing urban housing- stocks (original) (raw)
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Renewable and Sustainable Energy Reviews
Reducing the energy consumption of buildings is a priority for carbon emissions mitigation in urban areas. Building stock energy models have been developed to support decisions of public authorities in renovation strategies. However, the burdens of renovation interventions and their temporal distribution are mostly overlooked, leading to potential overestimation of environmental benefits. Life Cycle Assessment (LCA) provides a holistic estimation of environmental impacts, but further developments are needed to correctly consider spatio-temporal aspects. We propose a spatio-temporal LCA framework to assess renovation scenarios of urban housing stocks, integrating: 1) a geospatial building-by-building stock model, 2) energy demand modelling, 3) product-based LCA, and 4) a scenario generator. Temporal aspects are considered both in the lifecycle inventory and the lifecycle impact assessment phases, by accounting for the evolution of the existing housing stock and applying time-adjusted carbon footprint calculation. We apply the framework for the carbon footprint assessment of housing renovation in Esch-sur-Alzette (Luxembourg). Results show that the renovation stage represents 4% to 16% of the carbon footprint in the residual service life of existing buildings, respectively after conventional or advanced renovations. Under current renovation rates, the carbon footprint reduction would be limited to 3-4% by 2030. Pushing renovation rates to 3%, enables carbon reductions up to 28% by 2030 when combined with advanced renovations. Carbon reductions in the operational stage of buildings are offset by 8-9% due to the impacts of renovation. Using time-adjusted emissions, results in higher weight for the renovation stage and slightly lower benefits for renovation.
Proceedings of EnviroInfo and ICT for Sustainability 2015, 2015
The building sector represents one of the major sources of environmental impact due especially to space and domestic hot water heating and construction works. A number of studies focused so far on estimating the energy savings and carbon emissions reduction potential achievable by retrofitting urban building stocks, nevertheless a shift to life cycle assessment is needed to properly assess the environmental impacts in a more holistic way. The aim of this study is to develop a geospatial data model for the life cycle assessment of environmental impacts of building stocks at the urban scale. The methodology includes: geospatial processing of building-related data to characterize urban building stocks; a spatiotemporal database to store and manage data; life cycle assessment to estimate potential environmental impacts. The methodology was tested for a case study in Luxembourg and preliminary results regarding the retrofitting stage of residential buildings were provided for one entire city. The data model is part of a wider bottom-up framework being developed to support decision about building stock retrofitting for sustainable urban planning.
Energy and Buildings, 2016
A dynamic building stock model is applied to simulate the development of dwelling stocks in 11 European countries, over half of all European dwellings, between 1900 and 2050. The model uses time series of population and number of persons per dwelling, as well as demolition and renovation probability functions that have been derived for each country. The model performs well at simulating the long-term changes in dwelling stock composition and expected annual renovation activities. Despite differences in data collection and reporting, the modelled future trends for construction, demolition and renovation activities lead to similar patterns emerging in all countries. The model estimates future renovation activity due to the stock's need for maintenance as a result of ageing. The simulations show only minor future increases in the renovation rates across all 11 countries to between 0.6-1.6%, falling short of the 2.5-3.0% renovation rates that are assumed in many decarbonisation scenarios. Despite this, 78% of all dwellings could benefit from energy efficiency measures by 2050, either as they are constructed (31%) or undergo deep renovation (47%). However, as no more than one deep renovation cycle is likely on this timeframe, it is crucial to install the most energy efficient measures available at these opportunities.
A methodology for spatial modelling of energy and resource use of buildings in urbanized areas
2014
This paper presents and discusses a methodology for modelling energy and resource use of urban building stocks. The methodology integrates and further develops methodologies for energy, carbon and resource use analysis on building stocks with the aim of applying these to a case study of the City of Gothenburg, Sweden. Integrating geographical information systems (GIS) in the methodology for modeling of the building stock, allows assessment of the contribution and effect of various strategies to meet environmental goals for municipalities, portfolio owners, such as housing associations and institutional investors. The methodology identifies different development strategies including various options for refurbishment, add-on and new construction, which are evaluated with respect to their potential environmental impacts related to the life-cycle of the building, including construction and end-of-life options.
Energy and Buildings, 2017
In the building sector, the energy and the greenhouse gases embodied in the building materials are becoming increasingly important. Combined with the operational primary energy demand and the endof-life, the whole life cycle of buildings can be assessed. In this paper, a comprehensive method for calculating the life cycle of individual buildings is presented. First, their material composition has been determined and generic values for the embodied energy, embodied greenhouse gases, energy needed and greenhouse gases emitted during disposal of the different building materials have been calculated. Subsequently these values have been integrated into an urban energy simulation software to simulate energy and emission values for buildings. A given building geometry with four different building standards was considered. The results can help to decide between building refurbishment or demolition and new construction. For example it could be shown that the share of the life cycle stage production compared to the total value rises with a better building insulation standard, as the share of the use stage decreases. The highest building refurbishment standard resulted in the best life cycle performance when compared with less ambitious refurbishment or construction of a new building of today's standards.
Building and Environment
This study describes the results of Life Cycle Assessment (LCA) applied to 24 statistically-based dwelling archetypes, representative of the EU housing stock in 2010. The aim is to quantify the average environmental impacts related to housing in Europe and to define reference values (baseline scenario) for policies development. The average environmental impacts have been calculated taking into consideration the number of dwellings (clustered per typology, year of construction and climate zone) related to each representative model. System boundaries include production, construction, use (energy and water consumption), maintenance/replacement, and end-of-life phases of each dwelling. The environmental life cycle impact assessment was carried out using the ILCD method. EU average annual environmental impact per person, per dwelling, and per m 2 were calculated. Results show that the average life cycle greenhouse gases emissions related to housing per person per year are 2.62 t CO 2 eq and related to a representative dwelling per year are of 6.36 t CO 2 eq. The use phase (energy and water consumption) is the most relevant one, followed by the production and the maintenance/replacement phases. Single-family houses are responsible for the highest share of impacts related to housing in Europe. The same type of building has different impacts in different climatic zones, due to the differences in the need for space heating. In general, electricity use and space heating are the activities that contribute more to the overall impacts. The final results could be used as a baseline scenario for testing eco-innovation scenarios and setting targets toward impact reduction.
The identification of techno-economically feasible decarbonisation paths and sustainability transitions for the built environment is a necessary task for research today and building stock renovation processes can act in synergy with innovative economic and technological development paradigms to achieve different types of benefits such as economic growth and employment, together with resource efficiency and sustainability for the whole sector. The research presented aims at selecting the most relevant data analysis processes and techniques to respond to practical technical questions and to support decision-making in the built environment, at multiple scales of analysis, from individual buildings, to building stock and urban environment. The research aims to indicate in this way the possibility to join the micro-scale view, involving technological and behavioural issues in buildings, and the macro-scale view, involving strategic problems at market and policy levels for energy and sustainability planning. Further, the combined use of modelling techniques with large scale data acquisition and processing could guarantee multiple feed-backs from measured data, useful for the evolution, first of all, of design and operation practices in building but also, more in general, of the whole value chain of the sector. A synthesis and integration of modelling methodologies is presented through case studies, showing a path to improve transparency of performance assessment across building life cycle phases. Finally, multivariate data visualization techniques are presented to ease the use of the numerical techniques described, ensuring a wider applicability. 1 INTRODUCTION Buildings have a great impact in terms of carbon emission at the EU [1], US and global scale [2]. At EU level, for example, building accounts for approximately 40% of carbon emission, determined by their direct energy use, and a larger impact if we consider the direct and indirect use of resources. Different modelling approaches at the state of the art can be used for extracting useful insights for the support of building stock renovation processes, dealing with relevant technical issues. A detailed discussion on the suitability of energy modelling approaches with respect to multiple criteria can be found in literature [3]. Energy efficiency measures can create multiple advantages [4], but the increase of efficiency of energy systems strengthens the interdependency between design and operational optimization with an impact at multiple scales, from individual technologies, to single buildings, to building stock and infrastructures. This higher interdependency determines the need for formalized rules in optimization based approaches for energy research and practical applications [5], as well as the need for larger quantities of specific data for effective deployment of innovative strategies for built environment [6]. For this reason, a tight integration and comparability among different models is the focus of research. We should be able to pass from models to simulated data (model output, forward approach) and from measured data back to models (model input, inverse approach), in multiple ways, implementing effectively cycles of continuous improvement.
A scenario analysis of the life cycle greenhouse gas emissions of a new residential area
Environmental Research Letters, 2012
While buildings are often credited as accounting for some 40% of the global greenhouse gas (GHG) emissions, the construction phase is typically assumed to account for only around one tenth of the overall emissions. However, the relative importance of construction phase emissions is quickly increasing as the energy efficiency of buildings increases. In addition, the significance of construction may actually be much higher when the temporal perspective of the emissions is taken into account. The construction phase carbon spike, i.e. high GHG emissions in a short time associated with the beginning of the building's life cycle, may be high enough to question whether new construction, no matter how energy efficient the buildings are, can contribute to reaching the greenhouse gas mitigation goals of the near future. Furthermore, the construction of energy efficient buildings causes more GHG emissions than the construction of conventional buildings. On the other hand, renovating the current building stock together with making energy efficiency improvements might lead to a smaller construction phase carbon spike and still to the same reduced energy consumption in the use phase as the new energy efficient buildings. The study uses a new residential development project in Northern Europe to assess the overall life cycle GHG emissions of a new residential area and to evaluate the influence of including the temporal allocation of the life cycle GHG emissions in the assessment. In the study, buildings with different energy efficiency levels are compared with a similar hypothetical area of buildings of the average existing building stock, as well as with a renovation of an area with average buildings from the 1960s. The GHG emissions are modeled with a hybrid life cycle assessment. The study suggests that the carbon payback time of constructing new residential areas is several decades long even when using very energy efficient buildings compared to utilizing the current building stock. Thus, while increasing the overall energy efficiency is important in the long term, the construction of new energy efficient buildings cannot be used as a means to achieve the short term and medium term climate change mitigation goals as cities and governments often suggest. Furthermore, given the magnitude of the carbon spike from construction and its implications, the climate change mitigation strategies should set reduction targets for the construction phase emissions alongside the ones for the use phase, which currently receives almost all of the attention from policy-makers.
Energies
The scope of this study is to assess how different energy efficient renovation strategies affect the environmental impacts of a multi-family house in a Nordic climate within district heating systems. The European Union has set ambitious targets to reduce energy use and greenhouse gas emissions by the year 2030. There is special attention on reducing the life cycle emissions in the buildings sector. However, the focus has often been on new buildings, although existing buildings represent great potential within the building stock in Europe. In this study, four different renovation scenarios were analyzed with the commercially available life cycle assessment software that follows the European Committee for Standardization (CEN) standard. This study covers all life cycle steps from the cradle to the grave for a residential building in Borlänge, Sweden, where renewable energy dominates. The four scenarios included reduced indoor temperature, improved thermal properties of building materi...