Building Stock Model Research Articles

Assessing the prospective environmental impacts and circularity potentials of building stocks: An open‐source model from Austria (PULSE‐AT)

AbstractBuilding stock models can provide information on the current and future environmental impacts of buildings. Therefore, these models are useful tools for identifying trajectories that are compatible with the objectives of the Paris Agreement. However, the models often lack detail, which can lead to underestimations of the actual impacts of national building stocks, resulting in misinformed decision‐making. This study presents the steps needed to create an archetype‐based bottom‐up building stock model that uses Python and Brightway2. Prospective environmental assessments, including circularity assessments, can be performed by combining life cycle assessment (LCA) with material flow analysis (MFA). An important facet of this model is that it supports the development of a practical and easily reproducible method for the high‐precision modeling of a building stock. This model is open source, is readily adaptable to other countries, and does not require programming knowledge. This combined LCA‐MFA method can be used to assess the potential to reduce greenhouse gas (GHG) emissions from the Austrian building stock in five future scenarios involving sufficiency, energy, material, and design‐related measures. The results show different reduction potentials for embodied and operational GHG emissions depending on the set of measures taken. In all scenarios, mineral and synthetic materials contribute the most to embodied GHG emissions. Finally, the issue of validating building stock models is addressed, and numerous cross‐evaluations are proposed to ensure the reliability of results.

Improved energy retrofit decision making through enhanced bottom-up building stock modelling

Modelling the performance of building stocks is crucial in facilitating the renovation at the building stock level. Bottom-up building stock modelling begins by detailing individual buildings and then aggregates them into stock level. Its primary advantage lies in capturing the inherent heterogeneity among distinct buildings, which enables tailored retrofitting. Naturally, this approach requires a comprehensive dataset with detailed building information such as geometry and envelope thermal properties. However, a common challenge is the incompleteness of available data in individual datasets. To address this, previous bottom-up studies have filled the missing data with representative or statistical data. Such practice could lead to homogeneous modelling of distinctbuildings within the same statistical group. This limits the utilization of key ability of bottom-up building stock modelling in capturing heterogeneity, such as tailored retrofitting to explore potential retrofitting areas and strategies.To address this challenge of homogeneous modelling, we utilize data fusion framework for bottom-up building stock modelling, employing probabilistic record linkage and inverse modelling techniques to integrate multiple incomplete building performance datasets. This framework fills the missing data in one dataset with information from another, thus capturing inherent heterogeneity in the building stock. An empirical study was conducted in Umeå, Sweden, to investigate the framework’s effectiveness by modelling building stock with various retrofitting strategies. This study contribution lies in enhancing bottom-up building stock modelling by capturing inherent heterogeneity, to provide tailored retrofitting solutions.

From Material Cadastres to a Materiality Informed City Information Modelling

Abstract Urbanization and built environment significantly impact resource consumption, posing sustainability challenges, especially regionally, due to bulk material dominance. Circular practices, like closing, slowing, and narrowing offer solutions. However, effective circularity management requires understanding built environment material stock comprehensively. Material cadastres model city and regional materiality using typology approaches and GIS Modelling, offering insights into circularity potential and supporting strategic circular city management. Conversely, urban planning digitalization introduced City Information Modelling, linking GIS for urban structure mapping with Building Information Modelling systems for digital building integration and thus support urban planning. Yet, empirically, materiality and circularity issues lack systematic and comprehensive integration in such approaches. To this end, this paper discusses the potential of developing digital material cadastre concepts towards materiality-based urban information modelling using case study results that reveal strengths and limitations of existing cadastre concepts. We present a methodological overview covering a general approach to built environment material cadastres and the main components of the underlying bottom up Material Flow approach: material composition indicators and GIS based building stock modelling and a dynamization approach. To discuss circularity potentials of the built environment in a larger urban regional development context, we furthermore designed material cadastres for two case study cities and calculated exemplary circularity potentials for closing, slowing and narrowing approaches. The findings and drafted conclusions were then reflected with urban planning and development actors in workshops and group discussions. As a result, we present consolidated propositions with respect to bridging the methodological gap between strategic and operational materiality informed urban and regional planning in the transition of the built environment towards circularity.

Exploring the Influence of Household Agent-Based Modelling on Whole-life Decarbonisation of Residential Buildings

Abstract Besides the operational and embodied carbon associated with the physical building, how significant is the influence of the heterogenous nature of household decision making in whole-life decarbonisation of the housing sector? This paper investigates the effects of explicitly considering these factors through agent-based modelling (ABM) of households integrated in bottom-up building stock modelling considering typologies of physical houses (existing and new/future) and different households, and how these might evolve to 2050 in the State of Victoria, Australia. The state population is represented by household typologies based on socio-economic status, tenure, and decisions as influenced by financial, physical/family needs and behavioural factors. The ABM is implemented using Python MESA software and the different house typologies’ whole-life carbon are calculated using the Australian Zero Emission House (AusZEH) modelling software and the Environmental Performance in Construction (EPiC) LCA database, respectively. Considering household decisions yielded higher operational carbon reduction on average across various scenarios, however these have less impact on reducing embodied carbon. And in Victoria, with increasing trends in population and housing demand, embodied carbon dominates whole-life carbon (WLC) outcomes. The heterogeneity of household decisions cannot be ignored and should be further studied along with embodied carbon reduction strategies and a broad range of scenarios that consider the dynamic and uncertain nature of factors that drive and influence the WLC of buildings.

Dynamic analysis of carbon emissions from construction and demolition activities in Japan: Revealed by high-resolution 4D-GIS modeling

To meet the 2050 decarbonization target of the global buildings and construction sector, more attention is needed to reduce carbon emissions from construction and demolition. However, current national carbon accounting studies for these activities remain limited in spatial granularity and localized applicability. This study developed a bottom-up spatiotemporal database of carbon emissions from building construction and demolition in Japan via integrating a geographic information system-based building stock model, statistical data, and survey information. Focusing on municipal-level emissions, the Logarithmic Mean Divisia Index approach was used to decompose spatiotemporal variations and identify the contributing factors. Results indicate that carbon emissions from Japan's construction and demolition activities fell by more than 50% between 2005 and 2020, largely due to declining new/demolished-to-stock ratio, suggesting a transition to a stock-based society. Central cities' reliance on carbon-intensive buildings positively contributed to spatial variations in their construction emissions, underscoring the importance of sustainable materials and timber designs. Differences between prefectures in demolition emission intensity highlighted the strategic placement of recycling facilities in key regions to curb transportation-related emissions. Overall, these findings provided data reference for local governments to devise tailored policies for managing construction and demolition emissions.

Development of building stock model for an emerging city in India: Learnings for enabling circular economy in the built environment

AbstractThis study explores the prospects of urban mining for a steadily developing city “Thane,” located in the Mumbai Metropolitan Region of India, through building material stock accounting (BMSA). A novel bottom‐up approach for stock accounting was developed for the cities with limited data availability, through the integration of geodata spatial analysis, archetype identification through statistical modeling, and regional building design assessment for material intensity calculation. This study is the first of its kind in the Indian context and focuses on the stock estimation of the most common building materials: concrete, reinforcement steel, and masonry bricks within the boundaries of a typical Indian urban area. The results showed that the total built‐up stock in Thane city in 2018 amounts to 84.7 million metric ton (MT) by weight; concrete 57.7%, bricks 40.4%, steel 1.9%. Such reservoirs of raw material can be harnessed to fulfill the future material requirements of the construction industry through proposed circular economy interventions such as material bank creation, local recycling facilities, and development of a secondary material market. The material stock estimated in this study was 46.1 MT/capita for permanent building dwellers and with potential infrastructural developments underway, urban mining application can be ensured by redefining design and demolition strategies and multi‐level collaboration for generating alternative material sources for the construction sector. This work of BMSA intends to provide meaningful insights into exploring the potentials of urban mining and help chart the future roadmaps of sustainable construction in India.

Environmental performance of eco‐design strategies applied to the building sector

AbstractThe application of eco‐design principles in the building sector is considered a promising way to mitigate its substantial environmental impacts. However, quantitative evidence for this mitigation potential is lacking. The objective of this study was to quantify the environmental performance of diverse eco‐design strategies when applied to the building sector. A macroscale model capable of simulating the future demand for housing and related material flows within the urban building stock was developed based on an existing building stock model. These material flows were used to build inventories for a consequential life cycle assessment and, in turn, to quantify the potential environmental consequences of introducing eco‐design strategies in the building sector, assessed across 16 impact categories. Model outputs have a high level of uncertainty but are still useful for decision‐making, given the model's simplicity and transparency. The main results show that impact reductions can be obtained from specific uses of wood and wooden products, for example, when used for the walls in high‐rise buildings, whereas using hempcrete for partition walls increases the impact. Although the use of adaptability or disassembly strategies can reduce impacts, this pay‐off can only be obtained after a long period of implementation. In summary, the present study provides new quantitative insights into the ability of eco‐design strategies to mitigate environmental impacts in the building sector.

A value-based framework from Building Stock Model to Retrofit Model

The study has as its original database the decarbonization process initiated in Mexico by the National Commission for the Efficient Use of Energy (CONUEE) as part of its “Savings Program of Electric Power in Buildings of the Federal Public Administration” (PAEIAPF) of 1999. The primary purpose of PAEIAPF was to reduce the levels of electric power consumption in Federal Government buildings. The program has operated for 20 years; however, its scope only reaches operational carbon. Since 90% of existing buildings will be in use by 2050, the Retrofit Models will be the base to determine solutions for a more resilient living environment that fortifies and extends the grid’s capacity and meets climate change mitigation targets. Secondly, significant socioeconomic and profound environmental impacts are not calculated explicitly in existing tools and are often referred to as “secondary” or Non-Energy Benefits (NEB). “The goal is to give them a measurement value to be considered in the decision-making calculus. It is assumed that soon; such factors will enter the general climate change economy, not unlike carbon in the past decade.” In this context, the proposed research aims to develop a value-based framework that will support a Building Stock Model and subsequent Retrofit Models, documented in a web-tool platform. The framework has three main steps:A) Building Stock Model: Mapping of selected buildings of the program PAEIAPF in a GIS system. Documentation of the baseline energy consumption and embodied CO2-eq of the existing building.B) Retrofit Models: Involving a Whole Life Cycle Assessment (WLCA) and Non-Energy Benefits (resilience coefficient, health, productivity).C) Web Tool Platform: Application and toolset that allows for consistent documentation, environmental impact evaluation of existing building stock, and solution design in identifying energy reduction concepts.

Building Stock Models for Embodied Carbon Emissions—A Review of a Nascent Field

Building stock modeling emerges as a critical tool in the strategic reduction of embodied carbon emissions, which is pivotal in reshaping the evolving construction sector. This review provides an overall view of modern methodologies in building stock modeling, homing in on the nuances of embodied carbon analysis in construction. Examining 23 seminal papers, our study delineates two primary modeling paradigms—top-down and bottom-up—each further compartmentalized into five innovative methods. This study points out the challenges of data scarcity and computational demands, advocating for methodological advancements that promise to refine the precision of building stock models. A groundbreaking trend in recent research is the incorporation of machine learning algorithms, which have demonstrated remarkable capacity, improving stock classification accuracy by 25% and urban material quantification by 40%. Furthermore, the application of remote sensing has revolutionized data acquisition, enhancing data richness by a factor of five. This review offers a critical examination of current practices and charts a course toward an environmentally prudent future. It underscores the transformative impact of building stock modeling in driving ecological stewardship in the construction industry, positioning it as a cornerstone in the quest for sustainability and its significant contribution toward the grand vision of an eco-efficient built environment.

Comparative modeling of cost-optimal energy system flexibility for Swedish and Austrian regions

This study develops a reproducible method for estimating the cost-efficient flexibility potential of a local or regional energy system. Future scenarios that achieve ambitious climate targets and estimate the cost-efficient flexibility potential of demonstration sites were defined. Flexible potentials for energy system assessment are upscaled from the demonstration sites in Eskilstuna (Sweden) and Lower Austria (Austria). As heat pumps (HPs) and district heating (DH) are critical for future heat demand, these sites are representative types of DH networks in terms of size and integration with the electricity grid. In both regions a TIMES model is used for energy system optimization, while for upscaling, Eskilstuna uses the building-stock model ECCABS, whereas Lower Austria uses a mixed integer linear programming optimization model, and the BALMOREL power system model. According to the modeling, HPs will dominate Eskilstuna’s heating sector by 2040. In Lower Austria, DH becomes more prevalent, in combination with wood biomass and HPs. These findings are explained by the postulated technological-economic parameters, energy prices, and CO2 prices. We conclude that future electricity prices will determine future heating systems: either a high share of centralized HPs (if electricity prices are low) or a high share of combined heat-and-power (if electricity prices are high). Large-scale energy storage and biomass can be essential solutions as may deliver increased cost-effectiveness, if available and under certain conditions.

Producing domestic energy benchmarks using a large disaggregate stock model

Within the UK, domestic buildings account for 16% of total national emissions. Considerable improvements to the performance of the existing building stock will be necessary in the context of the UK’s commitment to emissions reductions, and for this to be achieved successfully and efficiently will require an improved understanding of the current performance of the stock. This paper presents an analysis of metered gas and electricity use from 808,559 dwellings with detailed building characteristic data in London, showing how energy use can be examined using a highly detailed, fully disaggregate building stock model. New gas and electricity benchmarks have been produced for houses (split by the level of attachment) and flats, for both gas- and electrically-heated properties. The paper shows how energy use varies with form, and how the choice of units influences the relative performance of different types. Comparing gas use across the types, for example, when calculated as kWh/m2, consumption follows building compactness, but when calculated as kWh/household, the trends follow building size. Finally, the paper examines how energy use varies with building thermal performance, using the Heat Loss Parameter (HLP), a standardised measure which accounts for thermal transfer through building envelopes as well as via air flow. Practical Application: This paper presents domestic energy consumption benchmarks based on measured not modelled data, produced from a large sample of London houses and flats. Results are shown for different dwelling types and heating fuels. Additionally, the relationship between gas use and envelope thermal performance is explored. The results will hopefully be beneficial for researchers, policy-makers and designers interested in better understanding current domestic energy use, and informing decisions about future improvements to energy efficiency within the stock. This paper also provides details for anyone interested in the production of the domestic benchmarks for the CIBSE benchmarking tool.

A modular framework for a dynamic residential building stock model with energy retrofit forecasts

Building retrofits are strongly dependent on the individual refurbishment/rehabilitation cycles of buildings. In order to achieve the targeted climate goals for the building sector, it is necessary to make the best possible use of refurbishment opportunities for energy retrofits. Furthermore, it must be considered that the younger the building, the lower the potential for energy savings. The most challenging, yet required, energy retrofits are all yet to come. Given the importance of the refurbishment cycle, the question arises as to what the theoretical refurbishment rate is, what the actual energy retrofit rate is, and what it needs to be in order to meet the climate targets for the residential building stock. The aim of this paper is to model the evolution of the size and retrofit status of national building stocks. This is to be done against the background of the deviation from the actual and theoretical refurbishment cycle. Using current statistics and the past development of the German residential building stock, central parameters like living space, new construction, deconstruction, and the retrofit rate are modeled endogenously. For the latter, influences of economic conditions are implemented through an exogenously set black box variable. The retrofit rate represents a deep energy retrofit and thus allows an easy connection of the model with energy parameters for building classes defined in the web database TABULA for 20 European countries. The results are of relevance for modeling the energy efficiency status of the building stock and deriving suitable conditions for increasing retrofit rates also in other countries. The results show that increasing the energy retrofit rates to 2%/a or more is largely unrealistic. Instead, the focus should be on weak points, especially where short-term savings are concerned. This applies in particular to facades, basement ceilings, and heating systems as well as the efficient use of energy in buildings.

Exploiting geographic open data to improve urban building energy simulations: The Padova city center case study

In recent years, building stock models have been developed by researchers to examine the aggregate performance of stacks of buildings within large areas, thereby giving rise to the concept of urban building energy models (UBEMs). The input data for such models consists of geometric and non-geometric attributes of the buildings, in addition to meteorological information. In this perspective, the acquisition of precise and comprehensive data poses a challenge, as the existing datasets often lack certain parameters or are not in a standardized format. This study aims to address the challenges by proposing a workflow for generating an input data frame tailored for incorporation into UBEMs. The data frame should include all the essential parameters of the buildings, and its constitution should be reflective of the real-world data. Moreover, the proposed workflow should remain consistent with databases available at national or regional levels. Acknowledging this non-uniformity in databases across regions, the methodology proposed in this study strategically considers various alternatives. For this reason, the proposed automatized workflow ensures flexibility and adaptability to changes in data availability. The workflow proposed in this study is a QGIS based geographical calculation method. The method can combine data from various sources into one shapefile that can be used to simulate the energy performance of buildings in urban areas.

Bottom-up LCA building stock model: Tool for future building-management scenarios

Residential buildings have a substantial impact on global environmental impacts. In this paper we present a model that assesses impacts from materials (embodied impacts) as well as from heating (operational impacts) for all residential buildings in Switzerland. Our model builds on an existing high-resolution spatio-temporal building stock model, which estimates the space heating demand of buildings, based on building property and site data. In this work we additionally include the impacts of materials extraction, production, transportation, and disposal of building components (floors, roofs, walls, ceilings and windows). Our model comes with a site- and building-specific default parametrization for all buildings, but it is developed as a tool that allows architects and planners to adapt building and site data with specific information to increase the accuracy of the environmental assessment of the current buildings and future building-management scenarios. We applied the model to ten Swiss buildings and assessed a selection of building-management scenarios to illustrate the application of the tool. The results show that our model estimates fairly accurate values of thermal and ventilation heat transmittance, operational space heating demand, and operational and embodied climate-change impacts for the considered buildings. The detailed modeling results for the ten case study buildings outperformed the simplified version of the model with generic default values for material building composition (using age-grouped building archetypes), emphasizing the importance of adding detailed material information in building life cycle assessments. Therefore, a focus should be placed on obtaining accurate material inventories of buildings in future research. The here-developed model allows for integration of such detailed material inventories, overwriting the provided default values.

Carbon and Greenhouse Gas Emissions from Electricity Consumption in European Union Buildings

The buildings sector is the single most important end-user of final energy in the European Union and a significant contributor to carbon and greenhouse gas emissions. This work focuses on a review of available data that are used to calculate the annual emissions from electricity generation in the European Union and quantify indirect emissions from the use of electricity in the buildings sector. Historical data since 1990 are used to derive simple empirical correlations for the time evolution of emissions factors related to electricity production in each Member State of the European Union. More recent trajectories using data from the last ten years are also presented. The derived correlations can be easily integrated in building stock modeling and national studies to facilitate forward-looking projections of emissions from electricity use in buildings. The EU-27 averages 0.2883 kgCO2-eq/kWhel, ranging from 0.0456 kgCO2-eq/kWhel in Sweden up to 1.0595 kgCO2-eq/kWhel in Poland. As a case study, the derived coefficients are then used to quantify the indirect emissions from the electricity consumption attributed to the building stock in each EU Member State. The calculated total EU-27 GHG indirect emissions attributed to electricity consumption amounted to 215 MtCO2-eq for residential buildings and 201 MtCO2-eq for non-residential buildings. In addition, the proposed correlations are used to demonstrate how they can be used for more realistic future projections of emissions towards the national targets in Greece and Poland.

Integrating bottom-up building stock model with logistics networks to support the site selection of circular construction hub

The circular construction hub is a logistics point for the storage, processing, and distribution of secondary construction materials. However, its site selection is dampened by the lack of detailed spatial information on material flows. In this study, the quantities and the spatial distribution of material flows are projected using a bottom-up building stock model. The material flows are integrated with logistics networks to assess the environmental impact of transporting materials between the building stock and the circular construction hub. The model is demonstrated on the building stock of Leiden, a municipality in the Netherlands. The results show that the location of future construction and demolition activities has a major impact on transportation carbon emissions. As construction decreases and demolition increases, the relative share of transportation carbon emissions from recycling will increase. The comparison between the two candidate sites for the circular construction hub is made to select the site with lower total transportation carbon emissions. By considering the evolution of building stock, the model can help urban planners make a more comprehensive decision on the location of the circular construction hub.

Gothenburg Digital Twin. Modelling and communicating the effect of temperature change scenarios on building demand

The article presents the first prototype of a web-based City Digital Twin (CDT) viewer developed for the city of Gothenburg to promote the understanding of the interrelation between the spatial, energy and climate change domain related to building stocks and to support stakeholders’ collaboration. The focus is on the development process of the viewer and decisions taken to target the users. 3d spatial data about the current city combined with building energy demand modelling following the Intergovernmental Panel on Climate Change scenarios provide the basis that potentially allows local actors to take informed decisions about decarbonization measures in a long-term perspective. First, future climate conditions are modelled for Gothenburg following the IPCC pathways 2.6, 4.5, and 8.5 for the year 2050. Second, a Building Stock Model is employed to simulate the energy use of buildings by using the climate scenarios as climate boundary conditions. Finally, results are visualized in the CDT viewer showing that future climate conditions contribute to an overall decrease in final energy demand up to 18% in spring and autumn months and an increase up to 1.5% in summer months.

National building stock model for evaluating the impact of different retrofit measures

In this study, a methodology was developed to evaluate different retrofit strategies, which allows an estimation of the current and future thermal space heating demand of the approximately 1.8 million residential buildings in Switzerland. The approach is based on a building stock dynamics model that considers new buildings, replacement buildings, demolitions, as well as past and current rates of energy-related retrofits. Different potential retrofit strategies are applied to evaluate their impact on reducing space heating demand. The results show the effectiveness of the distinct retrofit strategies in reaching the target reduction and emphasize the differences in the resulting annual retrofit rates. The simulated specific retrofit rates can serve as a basis for developing building retrofit measures at the national level, as well as for informing the next generation of regulations.

Public buildings: Life-cycle GHG emission scenarios and reduction trajectories by 2050

Responsible for 37% of global greenhouse gas (GHG) emissions, the construction and operation of buildings involves substantial potential to mitigate climate change. Although they represent only a small part of the building stock, publicly-owned buildings can lead by example and stimulate emission reductions through public procurement processes that are aligned with existing climate goals. In this paper, possible GHG emission reduction pathways for public office buildings in Austria are explored. A building stock model for Austria’s publicly-owned office buildings is developed, which projects operational and embodied GHG emissions from new construction, renovation and demolition until 2050. Findings show that phasing out fossil fuel use in building operations by 2050 enables GHG emission pathways that are compatible with the Carbon Law but still exceed Austria’s available carbon budget for public office buildings. A higher renovation rate can facilitate the fossil fuel phase-out by reducing energy demand. Embodied GHG emissions are becoming increasingly important and the main source of GHG emissions when phasing out fossil fuels in space heating. More research and policies are therefore needed to accelerate reductions of embodied GHG emissions towards net zero.

The effects of climate change-induced cooling demand on power grids

The trend towards equipping buildings with active space cooling technology is expected to continue, due to the warming climate. In addition, the electrification of mobility and industry, and the massive rollout of photovoltaics, may put Austria’s power grids under stress if adequate mechanisms are not implemented in time. This study investigates the magnitudes of the loads induced by this increasing demand for cooling, together with the relief that passive cooling measures can provide. Data from current climate models, measured real load profiles from households, building stock models, and dynamic building simulations are utilised, alongside stakeholder and expert opinions, to fine-tune the analysis. This article suggests plausible scenarios for the development of the demand for cooling energy in Austria until 2050, and analyses the aggregated effect of the different options for cooling on the electricity power grid. The integration of cooling loads is expected to cause overloads or voltage violations only for a few types of grid within the periods investigated here. Subsidy programs in the building sector often do not properly consider cooling demand. Building regulations and subsidies should therefore focus on passive measures, and only when these are not sufficient should measures related to active cooling be implemented.