A comprehensive approach to building-stock modelling - Assessing the impact of renovating urban housing stocks

The existing building stock provide a possibility for cost-efficient energy efficiency measuresand related reductions in greenhouse-gas emissions. As the rate of renewal in the buildingstockis low, energy efficiency measures need to be applied when renovation is being done inorder to reach climate goals. To increase the renovation rate and realise the potential forsubstantial reductions in energy use, several research and demonstration projects have beencarried out on both a European and Swedish level. In order to evaluate the current state andrenovation potential of the existing building stock on an urban level, a local approach isneeded to understand challenges and possibilities associated with the transformation of thebuilding-stock. To quantify the potential for reducing energy use and greenhouse-gasemissions, building-stock modelling is commonly used. However, these models are oftenbased on using representative buildings and scaling factors. With increased spatial resolution,building descriptions based on representative buildings lose accuracy and as a result,stakeholders operating at a planning or policy level are commonly targeted. This studyproposes a building-specific stock description where each building is treated individually todifferentiate the renovation potential within the building-stock. For this purpose, availabledatabases containing building-specific information has been gathered and processed for themulti-family building stock of the City of Gothenburg. The available data is used to create abuilding-specific stock description and renovation measures are modelled using a bottom-upengineering method and evaluated regarding energy use, environmental impact and costeffectiveness.This thesis with appended papers shows that available data sources can be usedto describe the characteristics of the stock on a building level and model the effect ofrenovation on energy use, environmental impact and cost-effectiveness in order to providedetailed information to policy makers, planners and property owners

Building Ownership, Renovation Investments, and Energy Performance—A Study of Multi-Family Dwellings in Gothenburg

The European building stock was renewed at a rapid pace during the period 1950–1975. In many European countries, the building stock from this time needs to be renovated, and there are opportunities to introduce energy efficiency measures in the renovation process. information availability and increasingly available analysis tools make it possible to assess the impact of policy and regulation. This article describes methods developed for analyzing investments in renovation and energy performance based on building ownership and inhabitant socio-economic information developed for Swedish authorities, to be used for the Swedish national renovations strategy in 2019. This was done by analyzing measured energy usage and renovation investments made during the last 30 years, coupled with building specific official information of buildings and resident area characteristics, for multi-family dwellings in Gothenburg (N = 6319). The statistical analyses show that more costly renovations lead to decreasing energy usage for heating, but buildings that have been renovated during the last decades have a higher energy usage when accounting for current heating system, ownership, and resident socio-economic background. It is appropriate to include an affordability aspect in larger renovation projects since economically disadvantaged groups are over-represented in buildings with poorer energy performance

Prioritizing deep renovation for housing portfolios

Cost-effectiveness of deep renovation has been assessed thoroughly on a building level. Such studies pro- vide limited guidance when prioritizing renovation measures for a building portfolio. On a stock level, building-stock modelling is commonly used to assess impact of renovation on a national and city level, targeting stakeholders operating at a planning or policy level. However, due to methodological choices and data availability, assessment of property owner portfolios is lacking. The aim of this paper is to cal- culate and spatially differentiate cost-effectiveness of deep renovation using equivalent annual cost and increase in assessed building value for a portfolio owner as a first step in prioritizing deep renovation within a building portfolio. A bottom-up engineering-based model is applied utilizing building-specific information for a municipal housing company portfolio in the City of Gothenburg, Sweden, consisting of 1803 multi-family buildings. Energy demand for space heating and hot-water is calibrated using mea- sured energy use from energy performance certificates. Deep renovation is assessed by applying a pack- age of measures across all buildings. Results show average energy use reduction across the portfolio of 51% to an average cost of 597 EUR/m 2 living area. While average energy cost savings account for 21% of equivalent annual cost, there are seven buildings where more than half the annual equivalent cost of renovation is covered by energy cost savings. Similarly, the distribution of change in assessed build- ing value is large for individual buildings, ranging from 0–23%. Aggregating results to larger areas tend to average out results while differences between individual buildings within areas persists. As such, the cost-effectiveness of deep renovation should be assessed on a building-by-building basis rather than for an area or neighbourhood. The results are intended as a first step in prioritizing deep renovation within a building portfolio and further detailed assessment is needed

Numerical Simulations and Empirical Data for the Evaluation of Daylight Factors in Existing Buildings in Sweden

Point Daylight Factor (DFP) has been used for daylighting design in Sweden for more than 40 years. Progressive densification of urban environments, in combination with stricter regulations on energy performance and indoor environmental quality of buildings, creates complex daylight design challenges that cannot be adequately solved with DFP. To support a development of the current and future daylight indicators in the Swedish context, the authors have developed a comprehensive methodology for the evaluation of daylight levels in existing buildings. The methodology comprises sample buildings of various use and their digital replicas in 3D, detailed numerical simulations and correlations of diverse DF metrics in existing buildings, a field investigation on residents\u27 satisfaction with available daylight levels in their homes, and a comparison between the numerical and experimental data. The study was deliberately limited to the evaluation of DF metrics for their intuitive understanding and easy evaluation in real design projects. The sample buildings represent typical architectural styles and building technologies between 1887 and 2013 in Gothenburg and include eight residential buildings, two office buildings, two schools, two student apartment buildings, and two hospitals. Although the simulated DFP is 1.4% on average, i.e., above the required 1%, large variations have been found between the studied 1200 rooms. The empirical data generally support the findings from the numerical simulations, but also bring unique insights in the residences\u27 preferences for rooms with good daylight. The most remarkable result is related to kitchens, typically the spaces with the lowest DF values, based on simulations, while the residents wish them to be the spaces with the most daylight. Finally, the work introduces a new DF metric, denoted DFW, which allows daylighting design in early stages when only limited data on the building shape and windows\u27 arrangement are available

Explorative life-cycle assessment of renovating existing urban housing-stocks

Urban building-stocks are responsible for a significant share of resource and energy use. To quantify the potential for reducing energy and environmental impact, building-stock modelling (BSM) is commonly used. Recently, the focus of BSM has expanded to include environmental impacts and life-cycle assessment (LCA). However, impact categories are often limited to climate change and representative buildings are often used. In addition, the future state of the stock is often calculated as a step-change to highlight the technical potential of an ideal future state. The aim of this paper is to assess the environmental impact of the future development of an urban housing-stock under business-as-usual scenarios using a building-specific GIS based model applied to the multi-family building stock of the City of Gothenburg. This paper uses an explorative LCA to account for environmental impacts based on dynamic uptake of common renovation measures and resulting energy savings until 2050. Two main scenarios are used where the renovation logic is based on either end-of-life of components or cost-effectiveness and further divided using limiting factors regarding investment capacity and annual share of the stock to be renovated. Results show possible energy savings of up to 23% and a corresponding 31% reduction in greenhouse-gas emissions. Greenhouse-gas emissions avoided due to reduced energy demand are offset by up to 65% by accounting for material use due to construction related renovation measures. For scenarios that favour construction related interventions, PV panels are responsible for the major part of the environmental impact across the 15 mid-point indicators used

A differentiated description of building-stocks for a georeferenced urban bottom-up building-stock model

Several building-stock modelling techniques have been employed to investigate the impact of energy efficiency measures (EEM), where the description of the building-stock generally consists of an age-type classification to specify building characteristics for groups of buildings. Such descriptions lack the appropriate level of detail to differentiate the potential for EEM within age groups. This paper proposes a methodology for building-stock description using building-specific data and measured energy use to augment an age-type building-stock classification. By integrating building characteristics from energy performance certificates, measured energy use and envelope areas from a 2.5D GIS model, the building-stock description reflects the heterogeneity of the building-stock. The proposed method is validated using a local building portfolio (N = 433) in the city of Gothenburg, where modelled results for space heating and domestic hot water are compared to data from measurements, both on an individual building level and for the entire portfolio. Calculated energy use based on the building-stock description of the portfolio differ less than 3% from measured values, with 42% of the individual buildings being within a 20% margin of measured energy use indicating further work is needed to reduce or quantify the uncertainty on a building level

A service-life cycle approach to maintenance and energy retrofit planning for building portfolios

\ua9 2019 The Authors Residential buildings account for almost a quarter of the total energy use in Sweden and building owners are, therefore, under pressure from policy makers to improve the energy performance of their buildings. Building portfolio owners (BPOs) generally face multiple barriers in energy efficiency investments such as financial constraints and lack of knowledge of the current state when planning energy efficiency measures. This paper presents a method for cost-optimal scheduling of maintenance and retrofit measures on a portfolio level by drawing on research on building stock modeling and maintenance retrofit planning. The method uses a building stock modeling approach to model costs, energy and greenhouse gas emissions (GHG)of a building portfolio and combines this with a method for optimal maintenance and retrofit scheduling in order to forecast and optimize the timing of measures on a building portfolio level. This enables the integrated long-term planning on retrofit investments and reduction of energy demand and GHG emissions for a portfolio of existing buildings. The application to the building portfolio of the municipal housing company of Gothenburg showed that by optimizing the maintenance and retrofit plans, ambitious retrofit measures can be introduced in the majority of the buildings with a positive effect on the service-life cycle costs. Moreover, the method is easily transferable to other building portfolios in Sweden as it builds up on nationally available data sets but is ideally complemented and verified using inspection data and existing maintenance plans of the BPOs in future applications

Stakeholder Specific Multi-Scale Spatial Representation of Urban Building-Stocks

Urban building-stocks use a significant amount of resources and energy. At the same time, theyhave a large potential for energy efficiency measures (EEM). To support decision-making and planning, spatial building-stock models are used to examine the current state and future development of urbanbuilding-stocks. While these models normally focus on specific cities, generic and broad stakeholder groups such as planners and policy makers are often targeted. Consequently, the visualization and communication of results are not tailored to these stakeholders. The aim of this paper is to explore the possibilities of mapping and representing energy use of urban building-stocks at different levels of aggregation and spatial distributions, to communicate with specific stakeholders involved in the urban development process. This paper uses a differentiated building-stock description based on building-specific data andmeasured energy use fromenergy performance certificates formulti-family buildings (MFB) in the city of Gothenburg. The building-stock description treats every building as unique, allowing results to be provided at any level of aggregation to suit the needs of the specific stakeholders involved. Calculated energy use of the existing stock is within 10% of the measured energy use. The potential for EEM in the existing stock is negated by the increased energy use due to new construction until 2035, using a development scenario based on current renovation rates and planned developments. Visualizations of the current energy use of the stock as well as the impact of renovation and new construction are provided, targeting specific local stakeholders

Spatial analysis of urban housing stocks

Urban building-stocks must be transformed in order to reduce energy and resource use to achieve climate change mitigation targets. As the rate of renewal in the building-stock is low, energy efficiency measures need to be applied when renovation is being done. In order to evaluate renovation potential of the existing building stock on an urban level, a local approach is needed to understand challenges and possibilities associated with the transformation of the building-stock. By incorporating building-specific information and also considering the building in its setting, a more holistic view can be achieved. For this purpose, available databases containing building-specific information has been gathered and processed for the multi-family building stock of the city of Gothenburg. The available data is used to describe the energy performance of the stock, future renovation needs and is used to create a description of the stock used as input for calculating the energy demand. This thesis with appended papers shows that available data sources can be used to describe the characteristics of the stock on a building level while considering the location and context. Building attributes such as year of construction, value year, property owner, geometric data and energy performance certificates is spatially linked as well as used in modelling the energy performance of buildings to provide detailed and valuable information to policy makers, urban planners and property owners

A review of Swedish residential building stock research

Energy usage in the Swedish building stock has changed significantly the last 20 years. The target of reducing the Green Houses Gas (GHG) emissions by 40% till 2020 seems reachable through improved energy efficiency and a switch to less GHG emitting heat sources. The goal of GHG neutrality by 2050 will however require further initiatives. This paper is primarily a review of the contemporary Swedish building stock state and research. Different research bodies, such as government research institutes, universities, and companies, have different financing and foci. They present their analyses the built environment differently. This paper creates a structure amongst these actors by dividing them in groups and by identifying topics where there are different positions held by researchers and practitioners in the fields related to building stock. Data from Energy Performance Certificates (EPC) is used to display how energy usage varies depending on building age. This gives an indication on how the building stock is developing and what possibilities there are to reach environmental targets