What is happening on Retrofit Standards?

BS 40104:2025 'Retrofit assessment for domestic dwellings' was published 24 Sep 2025 to provide a comprehensive framework for assessing homes prior to retrofit work. This Code of practice aims to enable better decision-making to enhance energy efficiency, occupant health, and long-term building performance.

What is BS 40104:2025 about?

BS 40104 provides a comprehensive framework for assessing homes prior to retrofit work. It addresses the lack of a standardized pre-retrofit evaluation by offering a whole-dwelling assessment approach to ensure that retrofit designs are appropriate for the specific characteristics, context, and usage of each home.

What does BS 40104:2025 cover?

BS 40104 provides a structured and detailed methodology for pre-retrofit assessment of domestic dwellings. It includes:

• Assessing the physical and contextual condition of the building.
• Evaluating ventilation and occupancy patterns.
• Understanding the energy performance of the home.
• Conducting site-specific assessments.
• Ensuring assessors meet defined competency standards.
• Reporting and lodgement procedures.
• Although it does not cover fire, gas, electrical safety, or structural evaluations, the assessor is expected to identify and report any visible risks in these areas during their assessment.

Who is BS 40104 for??

BS 40104 is intended for all professionals involved in domestic retrofitting, including:

• Retrofit assessors.
• Building surveyors.
• Architects and designers.
• Retrofit coordinators.
• Local authority officers and planners.
• Installers (ventilation, insulation, windows, doors, roofs).
• Certification bodies and consultancies.

It is relevant for sectors that support energy-efficient retrofit, such as manufacturers, installers, consultancy, and compliance certification. It is a key resource for practitioners working toward national retrofit targets.

Why should BS 40104 be used?

BS 40104 is an essential tool for improving the quality and outcomes of retrofit projects because it:

• Provides a formal benchmark for assessing retrofit readiness, improving consistency and reliability across projects.
• Reduces the risk of poorly designed or ineffective retrofit work by ensuring decisions are based on evidence and context.
• Supports alignment with the Each Home Counts review and builds on PAS 2035 and PAS 2030.

It enhances customer confidence, procurement transparency, and installer accountability, and is a vital component of the UK’s broader strategy to address fuel poverty, cut carbon emissions, and promote healthier living conditions. It ensures the first step of any retrofit project is based on sound data, comprehensive analysis, and best practice.

Does BS40104:2025 replace PAS 2035?

No, BS40104 is not replacing PAS 2035 entirely, but it replaces some parts, specifically the assessment clauses. BS40104 will provide a more detailed, specific standard for the retrofit assessment phase, focusing specifically on the assessment of dwellings for retrofit. It is designed to complement and formalize the assessment part of PAS 2035, which continues to provide the overall framework for the entire retrofit process, including assessment, design, specification, and installation.