Retrofitting at Scale: Accelerating Capabilities for Domestic Building Stocks

Retrofitting at Scale: Accelerating Capabilities for Domestic Building Stocks

What are the capabilities and capacities for delivering retrofit at scale?

The built environment faces an unprecedented challenge to rapidly decarbonise and reduce energy demand in the existing building stock.  However, the rate of retrofitting remains slow. This special issue explores the capabilities and capacities needed to deliver deep energy retrofit at scale. Looking across different scales – national, municipal, neighbourhood and individual sites — this special issue provides insights to shape policies, organisational structures and delivery strategies for different scales, building types and supply chain actors.

Guest editors: Faye Wade & Henk Visscher

New insights from research describe how the capabilities of building practitioners develop, how heritage building occupants manage energy, and how local authorities can help to coordinate retrofitting at scale. Papers in this issue have also provided new tools and techniques of value to researchers and practitioners alike. In particular, the issue includes: a typology of public sector energy service models; useful recommendations for developing RdSAP; and a new framework for moisture risk management in heritage buildings.

Key lessons and recommendations for government and industry stakeholders arising from this special issue include (but are not limited to):

  • Definitions of retrofit need to be more broadly framed to incorporate a vareity of measures.
  • Quality data and metrics for planning and evaluating retrofits are needed to ensure that performance outcomes match predictions.
  • Tools, techniques and building energy models are needed to plan and evaluate area-based retrofitting at scale.
  • New business models, contracts and financing are needed; these include performance guarantees.
  • A wider range of public sector and non-profit actors are needed to deliver retrofitting at scale. This will include: local authorities, social landlords and local citizen groups
  • Government-backed consumer protection is necessary: to provide clarity, oversight and reduce consumer risk.
  • Existing supply chains require additional support. Vocational and professional education and training needs to be fit for purpose in delivering energy retrofitting, including high-quality programmes and financial support to encourage existing workers to retrain.

Table of contents

Retrofit at scale: accelerating capabilities for domestic building stocks  [editorial]
F. Wade & H. Visscher

Domestic retrofit supply chain initiatives and business innovations: an international review
F. Brocklehurst, E. Morgan, K. Greer, J. Wade & G. Killip

Domestic retrofit: understanding capabilities of micro-enterprise building practitioners
K. Simpson, N. Murtagh & A. Owen

Housing retrofit: six types of local authority energy service models
M. Tingey, J. Webb & D. van der Horst

Retrofitting at scale: comparing transition experiments in Scotland and the Netherlands
P. Hofman, F. Wade, J. Webb & M. Groenleer

Determining the retrofit viability of Vancouver’s single-detached homes: an expert elicitation
J. McCarty, A. Scott & A. Rysanek

Rethinking retrofit of residential heritage buildings
F. Wise, A. Moncaster & D. Jones

Monitoring energy performance improvement: insights from Dutch housing association dwellings
H. S. van der Bent, H. J. Visscher, A. Meijer & N. Mouter

Retrofitting traditional buildings: a risk-management framework integrating energy and moisture
V. Gori, V. Marincioni & H. Altamirano-Medina

Launch Event - Videos

To promote wider discussion and participation, a joint event with CREDS (chaired by Nick Eyre, CREDS Director & University of Oxford) was held on 20 October 2021.  It addressed how retrofits for domestic buildings can be delivered at scale to meet climate targets in two specific ways:

  • Policy and governance for retrofitting
  • Developing supply chain capacity.

Watch the videos of Short Speaker and Respondent Presentations


Faye Wade Introduction to the special issue – key lessons
Petra Hoffman Retrofitting at scale: Comparing transition experiments in Scotland and the Netherlands
Janette Webb MBE Housing retrofit: six types of local authority energy service models
Joanne Wade OBE Domestic retrofit supply chain initiatives & business innovations: an international review
Kate Simpson Domestic retrofit: understanding capabilities of micro-enterprise building practitioners


Erwin Mlecnik, TU Delft
Veronika Schröpfer, Architects’ Council of Europe


Two respondents from the policy community briefly consider what they’ve heard and its policy impacts:
Stefan Moser European Commission, DG ENERGY, Head of Unit: Buildings and Products (ENER.B.3)
Lord Deben Chair, Climate Change Committee

These presentations were followed by a lively Q&A session.  There was broad agreement in each case that urgent action, coordination and capabilities are needed at many levels, particularly the role of local government.

The videos showcased here capture some of the speakers’ presentations, but not the audience dialogue.

Special Issue Abstracts

Retrofit at scale: accelerating capabilities for domestic building stocks [editorial]
F. Wade & H. Visscher

Retrofitting domestic buildings is essential for meeting targets to mitigate the catastrophic impacts of our changing climate. Current rates of retrofitting are far lower than necessary for achieving global net zero climate targets. To date in privately owned homes, policymakers have largely relied on piecemeal activity and often short-lived retrofitting programmes and financial incentives. Consequently, this special issue explores what capabilities and capacities are needed to deliver retrofit at scale. Looking across different scales—national, municipal, neighbourhood and individual sites—this special issue provides insights to shape policies, organisational structures and delivery strategies for different scales, building types and supply chain actors. These papers highlight the need for a clearer definition of what retrofit incorporates, alongside the collection of high-quality data and rigorous building metrics. In addition, diverse business models are needed to ensure that a variety of actors across the public and private sectors are well positioned to engage in coordinating building retrofit at scale. Finally, it is essential that any acceleration of retrofitting activity is coupled with consumer protection mechanisms and support for developing supply chains which incorporates both existing workers and encouragement for new entrants. It is only through this multifaceted approach that domestic building retrofit can be delivered at the speed and scale necessary.

Domestic retrofit supply chain initiatives and business innovations: an international review
F. Brocklehurst, E. Morgan, K. Greer, J. Wade & G. Killip

A systematic review of international evidence on housing retrofit supply chains was undertaken for the UK government: a Rapid Evidence Assessment (REA) summarised the most relevant research from outside the UK; key emerging themes were examined via analysis of 10 expert interviews with European and UK stakeholders, selected for the depth and breadth of their experience in developing retrofit business models. Market development requires concerted efforts from industry and policy, including the regulation of minimum standards. Conservatism in the industry means that opportunities for retrofit will be ignored in preference for the less risky, more familiar repair, maintenance and improvement (RMI) market. Successful retrofit involves customer engagement and after-care, which is outside customary practice. Financing mechanisms are important for firms’ cashflow and for customer acceptance. Skills governance needs to take account of national vocational education systems, and is more complex than simply providing a few new courses. Local partnerships are needed to mobilise and organise the supply chain, whether through local government involvement or new business models enshrining collaborative quality assurance. More formal quality assurance implies some consolidation of supply chains. All these elements must be integrated into a service package, whose overall purpose is to minimise the risks of retrofit for supply chains and customers.

Policy relevance: A functioning, large-scale energy-efficiency retrofit market needs to have some of the attributes of the existing RMI market, with energy performance grafted on. When compared with the ideal requirements for effective policy, existing policy support is inadequate, being too short-lived, too inconsistent and too easily sidelined by market realities. Retrofit requires high-quality outcomes achieved through integrated service, but construction industry business culture is focused on inputs (not outcomes) and the service is fragmented. Policy must help deliver a cultural shift, which no country has yet succeeded in bringing about. The task may be slow as it entails coordination and change across policy, education and vocational training, and industry practices.

Domestic retrofit: understanding capabilities of micro-enterprise building practitioners
K. Simpson, N. Murtagh & A. Owen

To deliver effective domestic retrofit at scale, it is essential to understand the current and required capabilities of building practitioners working in the repair, maintenance and improvement (RMI) of existing buildings. Capability research in the construction sector has previously focused on large projects, but small, and particularly, micro-firms that undertake RMI and form 77% of workers in construction, are under-researched. This gap is addressed by the present study on the capabilities of the practitioners and the contextual opportunities to deploy capabilities. The study analysed data from interviews (n = 27) with micro-enterprise building practitioners working in the UK’s RMI sector. Template analysis was conducted by applying an established model of behaviour change: Capability, Opportunity, Motivation—Behaviour (COM-B). Under Capability, three main themes were identified: knowledge, business management and individual characteristics. Under Opportunities, the main themes were state action, market and customer demand, technology diffusion, networks and business management. Under Motivation the themes were pride in work, good working relationships, maintaining a viable business and customer satisfaction. Practitioners are continually learning and problem-solving, developing trust and creating positive professional relationships. Working with these existing capabilities, experiential learning on-site and peer-to-peer training are recommended to scale up capability. For capabilities to be deployed, policy must enable opportunities across the multiple contexts micro-enterprise practitioners operate within, including training and incentives across the supply chain network and in stimulating demand.

Policy relevance: Policy-driven retrofit programmes, such as those providing government funding for retrofit, must work from existing practitioner capability to accelerate capacity and allow delivery at scale. Practitioner knowledge, built over generations, is used to solve problems encountered with existing buildings. Practitioners minimise risk by avoiding unfamiliar technologies and practices. Practitioners develop capability on-site, experientially, so policy must enable practical experience for practitioners. One aspect of capability that needs enhancement to deliver effective retrofit at scale is understanding the building as an integrated system. While learning about individual technologies is important, integrated knowledge of multiple technologies and how they work together is required. To develop industry capability, policy needs to recognise the essential role micro-enterprise practitioners play in delivering retrofit and to harness their existing capabilities in knowledge, problem-solving and business management. Opportunities are needed to develop retrofit capability through peer-to-peer learning, knowledge-sharing between older and younger practitioners, and influential sector networks.

Housing retrofit: six types of local authority energy service models
M. Tingey, J. Webb & D. van der Horst

Given the ambitious policy target to become net-zero carbon by 2050, what role can local authorities play in the decarbonisation of housing? An examination is presented of six local authority energy service models relevant to housing retrofit in Britain. Local authorities have an important role, with local knowledge about housing stock and economic opportunities; they also have relevant planning and governance responsibilities. However, relatively little is known about either the different energy service models adopted for retrofit, or their relative effectiveness. Models identified from empirical case study research constitute experimental innovations resulting from constrained finances and competition requirements in public services. They provided (1) energy efficiency upgrades to public, residential and commercial buildings, and/or (2) district heating infrastructure to secure ‘upstream’ resource efficiencies. Findings show that local initiatives provided different retrofit mixes, with differing potential for effective change. The limitations of current models are considered, along with the policy and market changes needed to empower local authorities to contribute systematically to net zero carbon buildings.

Policy relevance: How can British local authorities organise energy efficiency retrofit in buildings? Six energy service models are identified which deliver onsite energy efficiency upgrades and/or area-based efficient heating infrastructure. Reductions to energy demand from these models tend to fall short of the radical changes required by UK net zero 2050 goals. Whilst the energy service models provide examples of local innovation and effectiveness, much more ambitious policy is essential to enable a step change in energy service models for retrofit. Policy and regulatory changes are needed: first to reform the energy retail market to support energy services geared to reducing demand, and second to empower local authorities and their partners to scale up whole area retrofitting, including privately owned buildings.

Retrofitting at scale: comparing transition experiments in Scotland and the Netherlands
P. Hofman, F. Wade, J. Webb & M. Groenleer

New approaches are needed to achieve the scale and standard of building retrofit required to meet climate targets. Transition experiments are innovation projects that take a societal challenge as their starting point; they can be both top-down (government led) and bottom-up (civil society led). However, such experiments often remain isolated events that have little impact on delivering systemic change. There is limited knowledge on why this is so and what can be done to increase the success of experiments. The paper therefore compares the top-down approach to piloting Local Heat and Energy Efficiency Strategies (LHEES) in Scotland with the bottom-up strategy used for the Social Innovation Labs for a Zero Energy Housing Stock (SMILE) in the Netherlands. The different approaches are compared using three mechanisms to characterise systemic change: deepening, broadening and scaling up. Using data from interviews with local authority and citizen actors, the paper shows that neither top-down nor bottom-up experiments are sufficient in themselves to foster the new norms, information-sharing or legislative mechanisms needed to reach climate targets. The paper specifies elements of top-down and bottom-up experiments which can usefully be incorporated for achieving systemic change in energy retrofitting.

Policy relevance: Delivering building retrofit at scale is crucial to net zero greenhouse gas emissions targets. Policymakers can benefit from adopting long-term strategic approaches to retrofitting, incorporating leadership from local actors. Central government coordination is essential to providing a clear programme and timetable for local actors to coalesce around. In addition, localised projects need to be shared and supported through centrally coordinated repositories and knowledge exchange. Policymakers must develop complementary policies designed to improve support from both governmental and non-governmental actors. This will include planning and citizen engagement, managed at a local level; this is crucial for retrofitting buildings, which affects everyone directly. Neither top-down nor bottom-up approaches are sufficient in themselves to deliver systemic change in retrofitting. Central coordination, together with local planning and public engagement, will provide more opportunities to deliver retrofit at the speed and scale necessary for meeting climate targets.

Determining the retrofit viability of Vancouver’s single-detached homes: an expert elicitation
J. McCarty, A. Scott & A. Rysanek

The reduction in energy and emissions from the building sector can come from improved standards for new construction and retrofits to existing buildings. The retrofit viability for single-detached homes in Vancouver, Canada, is examined in terms of the key drivers and barriers involving economic and social forces. Local experts considered the likelihood of retrofits occurring to several archetypal dwellings that were synthesized from local building data and homeowner characteristics. The survey results (n = 56) raised less known but potentially significant issues regarding energy-efficiency retrofits in Vancouver. Domestic fuel switching, from fossil fuel energy services to electricity, is likely the most desirable future mechanism for decarbonizing homes. However, many of the respondents identified that Vancouver’s real estate market has a significant negative influence on retrofitting due to high land values, which results in a high demolition rate of existing homes. Only 46% of responses returned a view that an existing home would remain standing by 2050. In addition, 41% of responses expressed a doubt that the dwelling, whether existing or new, would achieve carbon neutrality by 2050. Both issues confront the City of Vancouver’s current emissions reduction planning, which has targeted near-complete decarbonization of the residential building stock by 2050.

Policy relevance: New construction is expected to account for only 30% of the greenhouse gas emissions reduction in Vancouver’s building sector. The potential for deep retrofits of single detached houses appear to be unlikely due to current real estate market conditions involving several perceived disincentives, e.g. low financial payback, poor knowledge, transaction costs, and the opportunity cost of new construction. If the widespread retrofit of single detached houses is a goal for cities that have high land-to-building value ratios, then the alteration of current market conditions is necessary. A basket of coordinated policy measures can be deployed to counter current market forces and reduce the demolition of existing homes. Such measures could include retrofit and planning codes, energy labelling, innovative finance, and public education.

Rethinking retrofit of residential heritage buildings
F. Wise, A. Moncaster & D. Jones

What are the opportunities and challenges for upscaling the energy retrofit of heritage buildings? Heritage buildings comprise approximately 20% of the UK building stock and are challenging to retrofit sensitively because of their heritage values and traditional construction. These buildings may therefore be unconducive to standard retrofitting approaches. Twelve case studies in the UK are examined. Three key findings are presented together with their implications for upscaling retrofit. First, heritage residents are found to engage in positive energy behaviours, which differ from standard assumptions and have a significant impact on energy demand. Second, standard energy models are shown to considerably overestimate the energy use within heritage buildings, failing to accurately portray both traditional construction and residents’ behaviours. Third, residents consider many common retrofits, such as replacement windows and wall insulation, to be unacceptable to their heritage values. A number of more acceptable and less invasive ‘soft retrofits’ were modelled and shown to have significant potential for reducing energy and carbon. Therefore, a more holistic approach to heritage building retrofitting needs to be taken, treating the complex interrelationship of buildings and their users as a system, and expanding notions of retrofitting to include soft retrofits and user behaviour.

Policy relevance: This research identified the importance of appropriately retrofitting heritage buildings, which include around 20% of the UK building stock. Standard solutions such as wall insulation and window replacement are unlikely to be enacted by most heritage residents because they are not acceptable to their heritage values, suggesting the need to prioritise other measures. Standard energy models such as Reduced data Standard Assessment Procedure (RdSAP) were found to be inaccurate for heritage buildings, overestimating energy use by both buildings and occupants, and should not be used to inform retrofit decisions for these buildings. Notions of retrofit should be expanded beyond fabric alterations to include behavioural changes and non-technical measures, including thermal curtains or shutters, which are more acceptable to residents and therefore more likely to be actioned. The potential exists to upscale retrofitting in heritage buildings, but approaches must consider specific user behaviour and view buildings and their occupants as interconnected systems.

Monitoring energy performance improvement: insights from Dutch housing association dwellings
H. S. van der Bent, H. J. Visscher, A. Meijer & N. Mouter

The Energy Performance of Buildings Directive (EPBD) enhanced the sustainable improvement of dwellings in the European Union. Member states formulated measurable goals to improve the housing stock, and monitoring systems were developed to give insights into the improvements. In the Netherlands, non-profit housing associations agreed to improve the quality of their housing stock to an average Dutch energy label B (energy index (EI NV) = 1.40) by 2020. Research assessing this progress over time is presented using an annual monitoring system based on 2.0 million energy performance calculations of 264 Dutch non-profit housing associations between 2017 and 2020. The assessment includes: a detailed description of the development of the state of the stock over time; the effect of changes to the stock (construction and demolition) and changes within the stock (different types of retrofit measures); and the different characteristics of non-profit housing associations. Insights from this research show which specific retrofit and other measures are adopted and have substantial impact over time. This provides a useful frame of reference for building stock analysis and accelerating the improvement of the building stock. It also creates a baseline of information for the future sustainable development of this particular stock.

Practice relevance: This research reveals which energy saving measures are most and least employed over time in Dutch non-profit housing associations sector. Large urban housing associations own a large share of the Dutch non-profit housing stock, and their dwellings have on average a lower energy rating. However, the improvement of their dwellings between 2017 and 2020 is higher than for smaller housing associations, which already have on average a higher energy rating. While the construction and demolition of dwellings contribute to 15.6% of the annual improvement, most of the improvement of the energy performance depends on retrofitting the existing stock. The trends are found to rely most on traditional measures (e.g. the installation of high-efficiency gas boilers and improved insulation). However, the rate of adding photovoltaic (PV) solar systems has increased rapidly in recent years, while futureproof systems (e.g. heat pumps and district heating) only have a steady adoption rate in this sector.

Retrofitting traditional buildings: a risk-management framework integrating energy and moisture
V. Gori, V. Marincioni & H. Altamirano-Medina

Traditional buildings constitute a large proportion of the building stock in many countries worldwide; around 40% of the UK’s housing stock was built before 1940 and was primarily made with solid masonry walls. Only 11% of UK solid-walled dwellings had insulation installed, suggesting the high potential of the low-carbon retrofit of traditional buildings. However, there is evidence of the occurrence of unintended consequences, often associated with excess moisture. A method is presented for moisture risk management that includes the development of a process and a framework. These tools are then integrated into a novel framework for the combined energy and moisture performance retrofit of traditional buildings. An example of the framework’s practical application is provided, with a focus on retrofit measures for solid-wall insulation. The proposed systematic approach demonstrates the interconnected nature of energy and moisture. It harmonises the principles needed to support organisations in the delivery of robust retrofit of traditional buildings through the integration of pre-retrofit building assessment and post-retrofit monitoring in the process. The risk-management process and framework presented can be valuable tools to support designers in providing robust and scalable retrofit measures and strategies.

Practice relevance: An integrated energy and moisture risk-management process is presented to support designers in the retrofit of traditional buildings. This is accompanied by a framework that explains the steps required for moisture risk management at the various stages of the retrofit process. This systematic approach harmonises the principles needed to support organisations in delivering robust low-carbon retrofits and integrates pre- and post-retrofit building assessment in the process. While previous work has addressed energy and moisture management separately, this integrates the two aspects into a framework for risk management. An example illustrates the relevant modes and methods of assessment and monitoring in support of risk management. When combined with practical guidelines and training, the risk-management process and framework can be valuable tools to provide robust and scalable retrofit measures and strategies. The framework was developed within the context of the UK construction industry; it can be adapted to other contexts.

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