image for illustration: Fiona Newton
The retrofit of the UK’s historic building stock is needed to enhance energy efficiency and achieve net zero targets, and the UK Parliament explores how this can this be done.
UK Parliament writes:
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’:
- 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. 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%. 80% of UK national building stock will still be in use in 2050, which is currently the oldest building stock in Europe. 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. 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. 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.
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, and is not currently considered an effective tool to inform initiatives. The government is consulting on reforms to the system.
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’. 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. 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).
Evidence suggests householders are not opposed to retrofitting but are unwilling or unable to bear the costs. 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. Evidence from previous schemes suggests customer awareness of the effectiveness of installed retrofit measures is low. 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. For example, ensuring retrofit assessments take account of damp, condensation, mould and overheating risks to address post-retrofit harms were highlighted.
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).
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’). Other concerns included the longevity of some retrofit products. For example, the thermal resistance of insulation materials can decrease, leading to ongoing replacement requirements.
There are also sub-standard installation risks, 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. Toolkits have been developed to increase awareness of how to evaluate, enforce and provide advice on retrofits for parties such as building control officers. 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, 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. 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.
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. Research suggests it may improve retrofit decision making in social housing.
- How to integrate retrofitting skills development and training in higher education and in vocational apprenticeships and training such as the Construction Skills Fund and the Construction Talent Retention Scheme. Contributors stated that innovative training methods on retrofitting and best practice are lacking for existing practitioners.
- Existing building certifications such as BREEAM, LEED, and WELL, 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, but capturing all the potential risks and benefits for retrofitting heritage buildings is challenging.
- 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. 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.
- The embodied emissions from building supply chains, including material sources, transportation, construction and demolition are linked to policy frameworks, regulation and global standards, and may be responsible for approximately 70% of an organisation’s total carbon footprint. 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).
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?
- 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?
- Whether building regulations need amending to reflect risk based retrofit approaches outlined in the BSi standard for retrofitting dwellings (PAS 2035:2023)?
- How can embodied carbon standards for buildings be developed nationally and internationally?
- What measures are required to address GHG emissions from building supply chains?
