PAS 2035 has become a cornerstone for retrofitting domestic buildings in the UK. It was developed in response to the growing urgency of reducing carbon emissions from the residential building stock and forms a central pillar of the government’s energy efficiency strategy.
At its core, PAS 2035 offers a comprehensive and structured methodology for improving the energy performance of domestic properties. It goes beyond basic compliance, aiming to ensure homes are not only energy-efficient but also safe, comfortable, and resilient to future challenges.
For anyone involved in housing retrofit projects—from local authorities and housing associations to private landlords and retrofit professionals—understanding PAS 2035 is essential for delivering high-quality, sustainable upgrades.
What is PAS 2035 and Why Does It Matter?
PAS 2035 is a publicly available specification that outlines how retrofit projects for domestic buildings should be assessed, designed, and verified. It was developed by the British Standards Institution (BSI) and launched in 2019 as part of the UK government’s broader push towards decarbonising buildings.
Crucially, PAS 2035 is part of a whole-house retrofit approach. It links directly to key policies and standards, including:
By following PAS 2035, stakeholders can:
- Achieve regulatory compliance and reduce risks
- Enhance occupant comfort and wellbeing
- Improve Energy Performance Certificate (EPC) ratings
- Secure funding and meet grant criteria
- Increase long-term asset value
The standard ensures that retrofit work is delivered in a way that is technically sound, people-centred, and environmentally responsible.
The Role of PAS 2035 in Retrofit Projects
PAS 2035 supports a coordinated, whole-building retrofit strategy for domestic dwellings. It promotes a fabric-first philosophy, which means improving insulation and airtightness before considering new heating systems or renewable energy technologies.
This approach ensures that retrofit measures complement one another, leading to better performance outcomes and long-term cost savings. Areas addressed include:
- Indoor air quality and ventilation
- Thermal comfort
- Energy efficiency
- Moisture control and building durability
Rather than isolated fixes, PAS 2035 calls for integrated solutions designed around the occupants’ needs and the unique characteristics of each home.
Timeline: The Development of PAS 2035
Pre-2018
Widespread concern about the performance of energy efficiency programmes prompts calls for a standardised approach to domestic retrofit.
2018
The Each Home Counts review recommends the creation of a new retrofit standard to address quality, performance, and accountability.
2019
BSI publishes PAS 2035 in tandem with PAS 2030:2019, creating a dual framework for the assessment, design, and installation of domestic retrofit projects.
2020–2023
The standard gains traction across government-funded schemes—particularly ECO3 and ECO4—and undergoes refinement based on practical implementation and industry feedback.
2023
PAS 2030:2023 is introduced, reinforcing alignment with PAS 2035:2023. The update includes enhanced digital compliance, stricter ventilation protocols, and competency requirements in preparation for full enforcement.
Ongoing
PAS 2035 continues to evolve to support emerging policy goals, workforce upskilling, and the development of data-led performance monitoring frameworks.
Who Needs to Comply with PAS 2035?
PAS 2035 is mandatory for all projects funded through government schemes such as the Energy Company Obligation. It is also increasingly adopted by local authorities, housing associations, and private developers seeking a best-practice framework for domestic retrofit.
Key parties required to comply include:
- Retrofit coordinators
- Installers and designers
- Assessors and evaluators
- Energy suppliers
Financial institutions and insurers also view PAS 2035 compliance as a mark of quality and reduced risk, encouraging wider industry adoption.
Key Requirements Under PAS 2035
PAS 2035 sets out several essential requirements to ensure retrofit projects are delivered to a high standard:
- Whole dwelling assessments
- Development of a medium-term improvement plan
- Occupant engagement and risk assessments
- Appointment of qualified professionals at each stage
- Quality assurance and post-installation evaluation
Each phase must be thoroughly documented to establish an audit trail and ensure transparency and accountability.
How to Conduct a PAS 2035 Assessment
The retrofit assessment is a key pillar of PAS 2035 and includes a series of evaluations designed to build a complete picture of the home. The process includes:
- Building condition surveys
- Occupant interviews and needs assessments
- Energy modelling
- Moisture risk assessments
These assessments inform the creation of a Whole Dwelling Retrofit Plan, which sets out the recommended measures and the sequencing of their delivery.
Understanding Retrofit Assessments in PAS 2035
Unlike traditional surveys, PAS 2035 assessments are multi-layered and occupant-focused. They must consider:
- Structural integrity and thermal performance
- Ventilation and air quality
- Lifestyle patterns and occupancy behaviour
- Future-proofing and adaptability
The assessor compiles this information into a Retrofit Assessment Report, which forms the foundation for all subsequent design and installation work.
Differences Between PAS 2035, PAS 2038, and PAS 2030
PAS 2030, PAS 2035, and PAS 2038 are Publicly Available Specifications developed by BSI (British Standards Institution) to provide best practice frameworks for energy efficiency and retrofit measures in buildings in the UK. Although related, each focuses on different types of buildings and aspects of retrofit delivery.
PAS 2030
PAS 2030 sets out the installation requirements for energy efficiency measures (EEMs) in existing dwellings. It is primarily aimed at contractors and installers and outlines how installation work must be carried out to a consistent and high standard.
PAS 2035
PAS 2035 defines a holistic, whole-house approach to domestic retrofit. It complements PAS 2030 by mandating that installations be specified, designed, and managed through a structured process led by qualified professionals. PAS 2035 is required for retrofit projects funded by government schemes like ECO (Energy Company Obligation).
PAS 2038
PAS 2038 provides a retrofit standard specifically for non-domestic buildings. It takes a similar whole-building approach as PAS 2035 but applies it to commercial or public sector buildings rather than homes. It supports meeting net-zero goals for the non-domestic building stock.
Summary Table: Key Differences
Feature | PAS 2030 | PAS 2035 | PAS 2038 |
Focus Area | Installation of energy efficiency measures | Retrofit coordination and design (domestic) | Retrofit process (non-domestic) |
Applies to | Domestic buildings | Domestic buildings | Non-domestic buildings |
Audience | Installers and contractors | Retrofit coordinators, designers, assessors | Building owners, consultants, energy managers |
Scope | How to install measures | Whole-house retrofit planning and delivery | Whole-building retrofit strategy and execution |
Driven By | Installation standards compliance | Risk-based, fabric-first, performance-driven | Performance, decarbonisation, life-cycle goals |
Linked Standards | Requires PAS 2035 for specification | Works in tandem with PAS 2030 | Independent, but aligned with PAS 2035 methods |
Mandatory For | ECO-funded installation work | All government-funded domestic retrofit schemes | Recommended for non-domestic retrofit (e.g. public sector decarbonisation) |
Introduced | First published 2013; updated 2019 | Introduced in 2019 | Published in 2021 |
Creating a Retrofit Strategy for Domestic Buildings
The Retrofit Plan is a central requirement under PAS 2035. Developed by the Retrofit Coordinator, it sets out the roadmap for implementing improvements in a safe, effective, and sequenced manner.
The plan includes:
Objectives and Performance Targets
- Targets may include reducing heating demand, achieving EPC band C, or addressing fuel poverty.
Risk Management Protocols
- Risks such as damp, overheating, or resident disruption must be identified and managed.
Procurement and Delivery Models
- Decisions about contractor selection, project phasing, and stakeholder engagement are outlined here.
Monitoring and Evaluation Plans
- Post-installation monitoring ensures measures perform as expected and support ongoing maintenance.
This structured approach aligns stakeholder expectations and provides a robust foundation for successful retrofit delivery.
Building Fabric Improvements under PAS 2035
Improving the building fabric is prioritised under PAS 2035. The goal is to minimise heat loss, control moisture, and enhance durability.
Key interventions may include:
- Loft, wall, and floor insulation
- Airtightness improvements
- High-performance glazing
- Cold bridge elimination
Attention to detail during design and installation is critical to achieving long-term benefits.
Managing Services and Utilities in PAS 2035
After addressing the fabric, attention shifts to building services. PAS 2035 promotes efficient, appropriately sized systems that respond to the needs of the household.
Examples include:
- Efficient gas or electric heating systems
- Mechanical ventilation with heat recovery (MVHR)
- Low-flow taps and efficient hot water storage
- Smart controls for heating and lighting
These upgrades improve energy performance while enhancing comfort and usability.
Monitoring and Verification Requirements
PAS 2035 includes robust quality assurance protocols. Monitoring includes:
- EPC assessments before and after retrofit
- Occupant satisfaction surveys
- In-situ performance monitoring, where feasible
These steps ensure that predicted improvements are realised and inform future upgrades or maintenance strategies.
The Retrofit Coordinator’s Role in PAS 2035 Projects
The Retrofit Coordinator is the cornerstone of any PAS 2035-compliant domestic retrofit. Acting as the project’s quality and compliance guardian, this individual ensures the retrofit process is safe, effective, and aligned with the standard’s requirements.
Their responsibilities include:
- Overseeing the full retrofit lifecycle, from assessment through design to evaluation
- Managing technical and project risks, including moisture, ventilation, and unintended consequences
- Coordinating communication between stakeholders, ensuring everyone is working to the same brief
- Verifying that all works and documentation meet PAS 2035 and PAS 2030 requirements
Retrofit Coordinators must be trained to Level 5 (or higher) in Retrofit Coordination and Risk Management and are typically accredited through TrustMark, which ensures consumer protection and technical compliance.
Their role is particularly vital in projects that involve vulnerable households, complex building types, or multiple retrofit measures.
Key Stakeholders and Their Responsibilities
A successful PAS 2035 project depends on collaboration between multiple qualified stakeholders:
- Building Owner/Client: Defines the strategic goals, secures funding, and signs off on final outcomes.
- Retrofit Assessor: Carries out a comprehensive dwelling assessment, covering condition, occupancy, ventilation, energy use, and heritage factors.
- Retrofit Designer: Translates assessment findings into technical specifications and coordinated designs.
- Retrofit Installer: Responsible for physically installing measures according to PAS 2030 standards and the approved design.
- Retrofit Coordinator: Oversees the process, manages risks, ensures documentation is complete, and confirms all professionals are appropriately certified.
All roles must be carried out by competent, accredited individuals, typically certified through TrustMark or organisations such as Elmhurst, Stroma, or The Retrofit Academy.
Training and Qualifications for PAS 2035 Practitioners
To operate effectively under PAS 2035, practitioners should hold or work towards the following qualifications:
- Level 5 Diploma in Retrofit Coordination and Risk Management (mandatory for Retrofit Coordinators)
- Domestic Energy Assessor (DEA) – for those conducting EPCs and assessments
- Certified Retrofit Assessor and Retrofit Designer qualifications
- Ventilation Installer certification, where mechanical systems are being installed
Ongoing CPD (Continuing Professional Development) is also strongly recommended in areas such as:
- Building physics and thermal bridging
- Moisture control and ventilation strategies
- Energy modelling software tools
This ensures practitioners remain up-to-date with evolving standards and technologies.
Documentation Required for PAS 2035 Compliance
A key strength of PAS 2035 is its structured, auditable approach. Required documents include:
- Retrofit Assessment Report
- Medium-Term Retrofit Plan (MTRP) – a roadmap for improvement over 20–30 years
- Design Specifications and Technical Drawings
- Installation and Commissioning Records
- Quality Assurance and Sign-Off Checklists
- Post-Installation and Occupant Feedback Reports
These records not only facilitate quality control, but are also essential for:
- Accessing public funding (e.g. ECO4)
- TrustMark compliance
- Future maintenance and performance reviews
Accurate documentation is vital for ensuring retrofit quality and accountability. It supports audits, protects clients and contractors, and enables long-term maintenance and performance tracking. Without it, projects risk non-compliance and may be ineligible for funding.
Certification Bodies and Accreditation Pathways
The following bodies provide training, oversight, or certification for PAS 2035-aligned professionals and projects:
- TrustMark (the government-endorsed quality scheme)
- Elmhurst Energy (Retrofit Assessor/Coordinator/DEA training)
- Stroma Certification (PAS 2030 installer schemes)
- The Retrofit Academy (comprehensive training and support)
Gaining PAS 2035 accreditation provides credibility, consumer protection, and access to funding programmes.
How to Pass a PAS 2035 Compliance Check
To pass a PAS 2035 compliance audit or TrustMark quality assurance check:
- Begin with a clearly defined project brief and set measurable performance goals (e.g. target EPC rating or carbon reduction)
- Engage accredited professionals early, especially the Retrofit Coordinator and Assessor
- Follow the standard’s structured process, from assessment to evaluation
- Keep detailed, version-controlled documentation
- Use interim QA and validation at key project stages, not just at the end
A well-maintained PAS 2035 checklist can help teams stay organised and ensure all tasks and roles are fulfilled on time.
The Economic Benefits of PAS 2035 Compliance
PAS 2035-compliant retrofit offers compelling financial and social returns:
- Reduced energy bills, particularly when fuel poverty is an issue
- Improved indoor air quality and health, lowering NHS and absenteeism costs
- Lower ongoing maintenance and repair costs
- Increased property value and appeal, especially for landlords
When combined with government support such as ECO4, LAD, or PAS 2035 projects often pay for themselves within a few years.
How PAS 2035 Supports Net Zero Goals
PAS 2035 underpins the UK’s pathway to net zero by:
- Enabling deep energy retrofit of homes, which account for ~20% of national carbon emissions
- Providing a framework for integrating low-carbon heating, insulation, and ventilation
- Supporting compliance with key legislation and policy goals (e.g. Clean Growth Strategy, Heat and Buildings Strategy)
It is also compatible with broader standards like ISO 50001, allowing alignment with corporate ESG strategies and social value outcomes.
Common Challenges in PAS 2035 Projects
Despite its benefits, implementing PAS 2035 can face hurdles:
- Low consumer awareness of retrofit standards
- Skilled labour shortages, particularly in PAS 2030-qualified installers
- Initial cost concerns, even when long-term savings are clear
- Technical complexity in older or solid-wall housing
These challenges highlight the need for continued training, support schemes, and public engagement.
Overcoming Barriers to Retrofit Adoption
Practical strategies to increase uptake include:
- Access to grants, 0% finance, and performance-based funding
- Expansion of retrofit training and apprenticeships
- Use of phased or “whole-plan” retrofit to manage disruption and affordability
- Public awareness campaigns emphasising long-term comfort, value, and sustainability
Framing retrofit as a strategic investment rather than a short-term cost is key to wider adoption.
How PAS 2035 Aligns with UK Government Policy
PAS 2035 aligns directly with several UK policy frameworks:
- Net Zero Strategy and Heat and Buildings Strategy
- ECO4 funding requirements (where PAS 2035 and PAS 2030 are mandatory)
- Fuel Poverty Strategy
- Building Regulations (Part L, Part F)
By conforming to PAS 2035, stakeholders demonstrate compliance with national energy, health, and housing targets.
Upcoming Changes to PAS 2035 Standards
Expected revisions to the PAS 2035 standard may include:
- Stricter indoor air quality targets
- Introduction of lifecycle carbon assessment metrics
- Improved guidance for digital monitoring, including smart meters and IAQ sensors
- Greater emphasis on post-occupancy evaluation (POE)
These changes will further integrate PAS 2035 into future-fit housing policy and performance metrics.
The Future of Domestic Retrofit and Energy Efficiency
As the urgency of climate action increases, PAS 2035 will become more central to housing strategy. We’re likely to see:
- Mandatory compliance for social housing and funded projects
- Expansion of accredited training, especially for installers
- Greater public engagement with retrofit opportunities
PAS 2035 is well-positioned to become the default quality standard for domestic energy improvements.
Final Thoughts on Achieving PAS 2035 Compliance
PAS 2035 provides a clear, structured, and proven route to safe, effective, and sustainable domestic retrofit. By following its guidance and involving qualified professionals, housing providers can improve the quality of homes while contributing to the UK’s net zero ambition.
Getting Started with Your PAS 2035 Journey
To begin:
- Review your housing stock and energy performance
- Engage a certified Retrofit Coordinator
- Develop a Medium-Term Retrofit Plan tailored to building type and funding route
Acting early enables access to funding, builds internal capacity, and delivers long-term economic and environmental benefits.
