Retrofit realism: affordable low-carbon policies for existing homes

Residential buildings are major users of energy and emitters of CO₂. They have long lifetimes and therefore decarbonisation of the heating and cooling of existing homes is critical for the goal of net zero emissions. The challenge of zero-carbon retrofitting also needs to address comfort in a warming world and affordability at scale. To address this problem will need improved building fabric and highly efficient, non-fossil, thermal systems. Technical solutions are known and available, but there are barriers to scaling up their deployment. Priorities for retrofit differ by climate zone and economic development status. In the Global South, rising temperatures are increasing cooling needs and the priority is to scale-up passive cooling approaches. In the Global North, heating demand is much greater and the key priority is a shift away from direct use of fossil fuels by electrifying heating, while accommodating growing cooling. Comprehensive policy interventions are required, including building and efficiency standards, regulations to phase out fossil fuel use, direct investment in thermal systems and fabric, incentives, financing, knowledge-sharing, and support for skills and training.

KEY FINDINGS

• Technical solutions for zero-carbon retrofit are known and commercially available.
• Both fabric improvements and changes to heating and cooling systems will contribute to decarbonisation.
• Electrification of heating and scaling passive cooling, both with high system efficiencies, are the key decarbonisation measures.
• Specific measures will depend on building type and climate.
• Universal access to electricity is essential and will be helped by the rapidly declining costs of distributed solar/battery systems.
• Building electrification should be taken forward in parallel with electricity decarbonisation.
• Heat decarbonisation will require electrification using heat pumps.
• Growth of energy use for cooling can be limited by scaling passive cooling approaches and high-efficiency technology standards.
• Retrofit provides potential multiple benefits for climate mitigation, energy security, affordability, productivity, comfort and health.
• Barriers include the required scale of investment, supply chain transitions and public support.
• Building retrofit needs long-term policy stability.
• International climate policy should support knowledge transfers to and from the Global South, with capacity-building, technology and finance to developing countries.
• National policy packages should include standards, investment in social housing, finance mechanisms, skills development, incentive programmes, and education and advice.