Table of contents
DOI: https://doi.org/10.58248/HS109
Overview
The greenhouse gas (GHG) emissions attributed to a building across its lifetime are known as its ‘whole life’ carbon emissions (PB 44)[1] and are commonly split into ‘operational’ and ‘embodied’:[2]
- Operational emissions are associated with the energy required to run a building (such as the energy used to provide lighting, heating, cooling and ventilation).
- Embodied emissions are associated with all the carbon embodied within the materials, structure, and supply chain for a building (such as those from the extraction, manufacture and assembly of a building’s materials and components, its repair, maintenance and refurbishment, demolition and end-of-life).
The Climate Change Committee identified the need to reduce emissions from buildings in the next three carbon budgets to achieve the 2050 net zero target, and estimated buildings produced 17% of UK GHG emissions.[3] In 2021, the UK Green Building Council estimated the UK built environment produced 25% of UK GHG emissions. If surface transport (vehicle emissions) is included within the scope of the built environment, this increases to 42%.[4]
80% of UK national building stock will still be in use in 2050, which is currently the oldest building stock in Europe.[5][6] Reducing building emissions may require retrofitting the existing stock of buildings to improve energy efficiency, reduce carbon emissions, preserve the embodied carbon in the existing fabric of the building and to enhance occupant comfort.[7][8] Contributors to the horizon scan suggested retrofitting could address both mitigation and adaptation to climate change, and help address risks such as overheating, poor indoor air quality and mould growth.[9]
In 2020, the UK Energy Research Centre estimated that almost half of the UK’s 29 million homes would need to be retrofitted to meet the 2050 net zero target.[10] Government incentives such as the Green Homes Grant, the Energy Company Obligation, the Renewable Heat Incentive and Heat Pump Grants (PN 699) have sought to promote retrofitting measures such as insulation and renewable energy installations, but have not achieved this rate of retrofitting.[11][12][13][14]
Challenges and opportunities
Heating, cooling, and ventilation systems play a significant role in the energy consumption and operational emissions of buildings. Contributors to the horizon scan suggested that to achieve the required rate of retrofitting to reduce the operational emissions of buildings involved addressing a range of challenges. For example, the national Energy Performance Certificate (EPC) database for domestic and commercial properties does not include data on retrofits unless a new EPC is lodged after retrofitting,[15][16]and is not currently considered an effective tool to inform initiatives.[17][18][19] The government is consulting on reforms to the system.[20]
Some research suggests that the most efficient way to deliver a domestic energy transition at scale may be a street-by-street approach or ‘area based retrofit’.[21][22] Area based retrofit involves undertaking retrofit projects in large numbers in one local area, which can bring together innovative forms of finance, contractor training, targeting and householder and community engagement.[23][24][25] This localised approach allows measures to be tailored to specific housing types, such as district heating for terraced houses, but is only possible where substantial grant funding is provided (PN 650)[26]
Evidence suggests householders are not opposed to retrofitting but are unwilling or unable to bear the costs.[27][28][29] Some contributors to the scan stated that communication of the processes and technologies involved in retrofitting to the public and industry needed to be addressed through approaches that prioritise education and engagement, with retrofit framed as an aspirational home improvement similar to the conversion to natural gas technologies in the 1960s.[30][31] Evidence from previous schemes suggests customer awareness of the effectiveness of installed retrofit measures is low.[32]
However, concerns were also raised that ventilation should be considered alongside insulation during retrofitting to avoid impacts on indoor air quality (PB 54) and realise health co-benefits.[33][18][34][35][36][37] For example, ensuring retrofit assessments take account of damp, condensation, mould and overheating risks to address post-retrofit harms were highlighted.[38][39][40][41]
Contributors stated that technological innovations are an opportunity for reducing building emissions. For example, smart building technologies, data analytics platforms and building management systems can enable real-time monitoring, predictive maintenance, and adaptive control by building users and owners. This could enhance energy efficiency by improving active and passive energy retrofit interventions, although occupant behaviours can cause increased energy use (PN 650)[42][43][44][45][46]
However, contributors raised concerns that the lack of processes, standards, post-occupancy evaluations or protocols for retrofit product testing in real homes, increased the chance they only achieve a fraction of the bill reduction expected (the ‘performance gap’).[47][48][49] Other concerns included the longevity of some retrofit products. For example, the thermal resistance of insulation materials can decrease, leading to ongoing replacement requirements.[50]
There are also sub-standard installation risks,[51][52][53]with contributors suggesting there is a need for more monitoring and verification of installed retrofits in homes to ensure they have no performance gap, or unintended consequences such as damp.[54] Toolkits have been developed to increase awareness of how to evaluate, enforce and provide advice on retrofits for parties such as building control officers.[55][56] Contributors also suggested that, rather than customers with failed retrofits being reimbursed, installers should be required to put them right.
The overall quality of the building stock was also raised as challenge, with a third of the cost of retrofits to repair defects before the retrofit takes place,[28] with no support for residents to make their houses retrofit ready. Several UK social housing sectors have been regulated to ensure homes are warmer and healthier for occupants.[57] It is more challenging to address in owner-occupied and the private rented sector, but the Government is currently consulting on proposals requiring rented properties to achieve an EPC rating of C.[58]
Key uncertainties/unknowns
- How the planning system can better reflect the value of existing buildings and avoid incentivising demolition and new buildings.
- Building Information Modelling, materials and facilities management systems can be integrated across the design, construction, and operational phases to optimise energy performance within existing buildings and minimise waste.[59] Research suggests it may improve retrofit decision making in social housing.[60][61][62][63]
- How to integrate retrofitting skills development and training in higher education and in vocational apprenticeships and training such as the Construction Skills Fund[64] and the Construction Talent Retention Scheme.[65] Contributors stated that innovative training methods on retrofitting and best practice are lacking for existing practitioners.
- Existing building certifications such as BREEAM,[66] LEED,[67] and WELL,[68] are not designed to drive retrofit installs or standards specifically, with no standardised monitoring and verification process to evaluate retrofits. The Pilot Version of the UK Net Zero Carbon Buildings Standard (The Standard) was launched by the built environment industry in 2024 includes retrofit,[69] but capturing all the potential risks and benefits for retrofitting heritage buildings is challenging.8,[70][71][72]
- The ease with which the operational energy efficiency of UK building stock can be improved in the timescale required to meet targets, such as the extent to which local authorities can build sufficient energy-efficient social housing and affordable housing.[73] Contributors suggested incremental changes to EPC band D then C then B would lead to inefficient short-term retrofitting choices.
- Whether strategies for insulating and retrofitting buildings will help to address inequalities.[74]
- The embodied emissions from building supply chains, including material sources, transportation, construction and demolition are linked to policy frameworks, regulation and global standards,[75] and may be responsible for approximately 70% of an organisation’s total carbon footprint.[76] Barriers to adopting more sustainable building supply chains include high capital costs, education across multiple tiers of the supply chain and the specialised skills and innovations needed to take account of the interdisciplinary nature of supply chain sustainability standards (including ethics and transparency).[77][78][79][80][81][82]
Key questions for Parliament
- How can retrofit of UK building stock be achieved through regulatory incentives that provide certainty over decades? How can the number of similar policies with slightly differing eligibility requirements and rules be addressed to reduce confusion among those bidding for funds?[83]
- What further incentives, such as grants and schemes, are needed for energy and fabric upgrades to UK building and housing stock? Rather than basing grants on upgrades to EPC scores, should they be targeted on the most effective measures?[84]
- Whether building regulations need amending to reflect risk based retrofit approaches outlined in the BSi standard for retrofitting dwellings (PAS 2035:2023)?[85][86]
- How can embodied carbon standards for buildings be developed nationally and internationally?
- What measures are required to address GHG emissions from building supply chains?
Relevant documents
Energy Security and Net Zero Committee (2024). How do we retrofit UK homes for net zero?
House of Commons Library, The construction industry: statistics and policy
House of Commons Library Research Briefing, The Energy Company Obligation
House of Commons Library Research Briefing, The Renewable Heat Incentive
House of Lords Library Briefing, Construction Sector: Modernisation and Sustainable Housing Supply
Reducing the whole life carbon impact of buildings, POSTbrief 44
Environmental housing standards, POSTnote 650
Green skills for education and employment, POSTnote 711
References
[1] There is no agreed single figure for the whole life carbon emissions from buildings in the UK, but the World Business Council for Sustainable development estimate the built environment represents over 33% of global final energy use, generates nearly 40% of global energy-related GHG emissions and consumes 40% of global raw materials: World Business Council for Sustainable Development, Transforming the Built Environment
[2] RICS (2023). Whole life carbon assessment (WLCA) for the built environment. .
[3] Climate Change Committee. (2024). 2024 Progress Report to Parliament
[4] UKGBC. (2024). Net Zero Carbon Buildings Framework.
[5] LETI (2024). Climate Emergency Retrofit Guide.
[6] UKGBC. Home Retrofit
[7] Architect’s Journal (2019). RetroFirst – A campaign by the Architects’ Journal.
[8] This includes heritage and grade-listed buildings. Historic properties make up a significant proportion of the UK’s building stock, with 5.9 million buildings constructed before 1919 and a further 4.3 million (15%) before 1944. There are approximately 350,000 listed dwellings in England, and an estimated 2.8 million homes in conservation areas. Retrofit of these buildings can be more challenging and costly due to the specific skills and materials required, along with additional permissions required in some cases. However, successful retrofit prevents waste and allows continued use and care for the building and is beneficial in lifecycle carbon terms compared to demolishing and renewal (DESNZ. (2024). Adapting historic homes for energy efficiency: a review of the barriers, GOV UK).
[9] Liyanage, D. et al. (2024). Climate adaptation of existing buildings: A critical review on planning energy retrofit strategies for future climate. Renewable and Sustainable Energy Reviews, Volume 199, 114476
[10] Rosenow, J. et al. (2020). The pathway to net zero heating in the UK. UKERC
[11] Department for Business, Energy & Industrial Strategy (2020). Apply for the Green Homes Grant scheme. GOV.UK.
[12] GOV.UK. (2022). Design of the Energy Company Obligation ECO4: 2022-2026.
[13] GOV.UK (2014). Domestic Renewable Heat Incentive (RHI).
[14] GOV.UK. (2021). Heat pump grants.
[15] GOV.UK. Find an energy certificate
[16] ONS. (2024). Energy efficiency of housing in England and Wales: 2024
[17] An EPC is required to sell or rent a property, as well as for newly built properties and should be renewed every ten years (Energy Performance Certificates, GOV UK). A display energy certificate is required annually for public buildings and those occupied by public authorities which have a total useful area greater than 250m2 and provide a public service to a large number of people (Check a public building’s Display Energy Certificate, GOV UK)
[18] National Retrofit Hub. (2024). EPC Reform
[19] Hardy, A and Glew, D. (2019). An analysis of errors in the Energy Performance certificate database. Energy Policy, Volume 129, Pages 1168-1178
[20] MHCLG & DESNZ. (2024). Reforms to the Energy Performance of Buildings regime
[21] University of Leeds. (2024). Improving home retrofit policies with place-based solution
[22] Owen, A. et al. (2023). Who applies for energy grants? Energy Research & Social Science, Volume 101, 103123
[23] Merrick, N. (2023). What does a place-based, citizen-led approach to retrofit look like? Carbon Co-op.
[24] Gupta, R. and Gregg, M. (2020). Domestic energy mapping to enable area-based whole house retrofits. Energy and Buildings, Volume 229, 110514
[25] IPPR. (2023). More than money: Moving towards a relational approach to retrofitting.
[26] https://livingwithgas.substack.com/
[27] Fylan, F. et al. (2016). Reflections on retrofits: Overcoming barriers to energy efficiency among the fuel poor in the United Kingdom. Energy Research & Social Science, Volume 21, Pages 190-198
[28] City Intelligence. (2022). Londoners’ awareness and understanding of retrofitting
[29] New Economics Foundation. (2021). Great Homes Upgrade: An investment and policy package to futureproof UK housing.
[30] Johnson-Schlee, S. (2022). ‘Brighter lives are lived by gas!’: how natural gas was sold to a sceptical public in post-war Britain. The Conversation.
[31] Betteridge, K. et al. (2024). Warmer Homes: How can Grant Subsidy Schemes Improve Engagement with Participants? A British Academy Policy Insight Case Study Grant
[32] Adebisi, W. et al. (2024). Towards Energy Efficient homes: A review of retrofitting policies in the UK. International SEEDS Conference Paper.
[33] Gupta, R, and Howard, S (2021) Pre-retrofit monitoring of indoor air quality and energy use in a low-rise block of flats in the UK. Proceedings of Building Simulation 2021 conference, 1-3 September 2021, Bruges
[34] Milner, J et al. (2023). Impact on mortality of pathways to net zero greenhouse gas emissions in England and Wales: a multisectoral modelling study. The Lancet Planetary Health, Volume 7, Issue 2e128-e136
[35] Gupta, R, and Berry, C. (2023). Examining the concentrations and trends in indoor air quality in existing UK social housing dwellings, Proceedings of the Healthy Buildings Conference 2023, 11-14 June 2023, Aahen, Germany.
[36] Gupta, R, and Howard, A. (2022). Exposure to indoor air pollutants in a deep energy retrofit of a block of flats in UK. Proceedings of Indoor Air 2022, 12-16 June 2022, Finland
[37] Gupta, R. and Kapsali, M. (2016) Empirical assessment of indoor air quality and overheating in low-carbon social housing dwellings in England, UK. Advances in Building Energy Research, 10 (1), pp.46-68
[38] DESNZ. (2024). DEEP Report 1: Synthesis, Demonstration of Energy Efficiency Potential
[39] Guttridge-Hewitt, M. (2024). Helping social housing landlords avoid retrofit nightmares. The Environment Journal
[40] Recart, C. and Dossick, C. (2022). Hygrothermal behaviour of post-retrofit housing: A review of the impacts of the energy efficiency upgrade strategies. Energy and Buildings, Volume 262, 112001
[41] Gbolade, T., and Kajang, K. (2024). Retrofitting at scale: tackling hard-to-treat properties. Inside Housing.
[42] RINNO. Welcome to the RINNO Project. Building a Low Carbon, Climate Resilient Future: Secure, Clean and Efficient Energy
[43] Northumbria University Newcastle. DigiBE – Digital Built Environment.
[44] Harputlugil, T., and de Wilde, P. (2021). The interaction between humans and buildings for energy efficiency: A critical review. Energy Research & Social Science, Volume 71, 101828
[45] Peñasco, C., and Anadón, L. (2023). Assessing the effectiveness of energy efficiency measures in the residential sector gas consumption through dynamic treatment effects: Evidence from England and Wales. Energy Economics, Volume 117, 106435
[46] Wingrove, K., et al. (2024). Increased home energy use: unintended outcomes of energy efficiency focused policy. Building Research & Information, Volume 52, Issue 5
[47] Hardy, A. (2021). The uncertainty around uncertainty. Leeds Beckett University
[48] Zheng, Z. et al. (2024). Review of the building energy performance gap from simulation and building lifecycle perspectives: Magnitude, causes and solutions. Developments in the Built Environment, Volume 17, 100345
[49] Mahdavi, A., and Berger, C. (2024). Ten questions regarding buildings, occupants and the energy performance gap. Journal of Building Performance Simulation
[50] DESNZ. (2024). Deterioration of retrofit insulation performance (DRIP): Phase 1
[51] DESNZ and Ofgem. (2025). What to do if you have poor quality wall insulation
[52] Conway, Z. (2025). ‘Serious and systemic’ problems found in insulated homes. BBC
[53] HomeOwners Alliance. (2025). Solid wall insulation problems: government warning.
[54] May, N. and Sanders, C. (2019). BSI White Paper: Moisture in Buildings
[55] Birmingham City Council (2024). Guidance Toolkit on Building Retrofit
[56] City of London. (2024). Heritage building retrofit toolkit
[57] For example, Scottish Housing Regulator
[58] Department for Energy Security and Net Zero. (2025). Improving the energy performance of privately rented homes: 2025 update
[59] RIBA Digital Overlay, (2024). Smart Building Overlay to RIBA Plan of Work.
[60] Tzortzopoulos, P. et al. (2019). Evaluating Social Housing Retrofit Options to Support Clients’ Decision Making—SIMPLER BIM Protocol. Sustainability, 11(9), 2507
[61] BiMPLUS. (2021). BIM software drives net zero social housing retrofit
[62] Livingston, E. (2022). A blueprint for how housing associations can use BIM. Inside Housing.
[63] Little, S. (2022). How data improves social housing retrofit decisions. MEARS
[64] CITB (2021). Construction Skills Fund – CITB.
[65] CLC (2021). Construction Talent Retention Scheme. [Accessed 25 Jun. 2024].
[66] BRE (2022). BRE Academy (BREEAM).
[67] USGBC (2020). LEED Rating System..
[68] WELL (2022). WELL Standard.
[69] UK Net Zero Carbon Buildings Standard (2024). Pilot Version rev1
[70] MHCLG, DCMS and DESNZ (2023). Adapting historic homes for energy efficiency: a review of the barriers
[71] Historic England (2024). Heritage and the Pathway to Net Zero
[72] Sodangi, M., and Salman, A. (2024). Analysing the Critical Impediments to Retrofitting Historic Buildings to Achieve Net Zero Emissions. The Open Construction & Building Technology Journal
[73] The Commission on a Gender-Equal Economy. (2020). Creating a caring economy: a call to action. Executive Summary.
[74] Atherton, G. and Webb, C. (2022). Levelling Up. What is it and can it work? Centre for Inequality and Levelling Up (CEILUP) at the University of West London
[75] For example, the Task Force on Climate-related Financial Disclosures
[76] Greenhouse Gas Protocol (2019). Greenhouse Gas Protocol.
[77] Chopra, S. et al. (2024). Navigating the Challenges of Environmental, Social, and Governance (ESG) Reporting: The Path to Broader Sustainable Development. Sustainability, 16(2), 606
[78] Vaverková, M. et al. (2024). Enhancing Sustainable Development Through Interdisciplinary Collaboration: Insights From Diverse Fields. Sustainable Development.
[79] Anholon, R. et al. (2024). Training Future Managers to Address the Challenges of Sustainable Development: An Innovative, Interdisciplinary, and Multiregional Experience on Corporate Sustainability Education. World, 5(2), 155-172
[80] Patil, V. et al. (2022). Supplier sustainability: A comprehensive review and future research directions. Sustainable Manufacturing and Service Economics, Volume 1, 100003
[81] Budler, M. et al. (2023). A review of supply chain transparency research: Antecedents, technologies, types, and outcomes. Journal of Business Logistics, Volume45, Issue1, e12368
[82] Gelsomino, M. et al. (2023). Addressing the relation between transparency and supply chain finance schemes. International Journal of Production Research, Volume 61, Issue 17
[83] DESNZ. (2024). Help to save households money and deliver cleaner heat to homes
[84] DESNZ (2024). Demonstration of Energy Efficiency Potential (DEEP). GOV.UK
[85] BSI. PAS 2035 – Retrofitting Dwellings for improved Energy Efficiency
[86] Currently building regulations and best practice retrofits require internal wall insulation to achieve a 0.3 U value, which may increase interstitial condensation risks. The risk based retrofit approaches outlined in PAS2035 suggest a U value of 0.8 achieves most of the energy savings without increasing these risks.
Image credit: Delia_Suvari via Adobe Stock
