PAS 2035:2023, MCS, Trustmark, Warm Homes

Sponsored by the UK Government’s Department for Business, Energy and Industrial Strategy (BEIS), this PAS is a key document within a framework of new and existing standards for conducting effective energy retrofits of existing buildings. PAS 2035:2023 covers how to assess dwellings for retrofit, identify improvement options, design and specify Energy Efficiency Measures (EEM) and monitor retrofit projects. Meanwhile, PAS 2035:2023, which was redeveloped in conjunction with PAS 2035:2023, covers the installation, commissioning and handover of retrofit projects. Organisations which trade using the TrustMark Government-endorsed Quality scheme are required to comply with PAS 2035:2023.

Who is PAS/MCS for?

All those engaged in the management, design and installation of energy efficiency measures in existing buildings, including;

• Retrofit Advisors, Assessors, Co-ordinators, Designers, Evaluators and Installers working in
• Commercial building contractors
• Specialist installers of retrofit measures
• Local SME builders and independent tradespeople working alone or in small teams
• Certification Bodies

Why should you use PAS/MCS?

It specifies requirements for the retrofit of dwellings, including:

• Assessment of dwellings for retrofit
• Identification and evaluation of improvement options (Energy Efficiency Measures, or EEMs)
• Design and specification of EEMs (whether individual measures or packages of multiple measures)
• Monitoring and evaluation of retrofit projects
• Installation, commissioning and handover

The PAS/MCS also covers a comprehensive range of EEMs that are intended to improve, among other things, the insulation of building fabric elements and air tightness, and to provide, among other things, efficient heating and cooling systems with smart controls, including systems using low- or zero-carbon (LZC) technologies.

In addition to setting out requirements of all of the above, PAS 2035:2023 also specifies requirements for advising building occupants about improvement options appropriate to their homes, and the efficient and appropriate use and maintenance of their retrofitted homes as well as for monitoring and evaluating retrofit projects when appropriate, and feeding back lessons learned to all parts of the supply chain, including the building occupants.

This PAS covers work that is initiated, procured, funded and delivered in a variety of ways, including:

• Retrofit programmes promoted and/or funded by national or local government schemes, e.g. Warm Homes Plan
• Retrofit programmes initiated and/or funded by landlords, including social housing organisations, private landlords in the domestic sector and commercial property portfolio holders
• Retrofit of individual buildings by their owners and/or occupants, including both domestic and commercial owner-occupiers
• Retrofit that is integrated with and forms part of broader repairs, maintenance and improvement (RMI) activity related to individual buildings or building stocks

NOTE 1: Many aspects of domestic retrofit are covered by existing standards. Where appropriate, those standards are referred to in PAS, and compliance with them is thereby a requirement of PAS.

NOTE 2: This PAS/MCS does not apply to maintenance or repair of any element of an existing dwelling, or system installed in it, which does not involve improvement of the energy performance or ventilation of the dwelling, or a reduction of the carbon dioxide emissions associated with energy use in the dwelling. Nor does PAS/MCS apply to “like-for-like” replacement of damaged or worn-out elements or systems that do not involve improvement of the energy performance or ventilation of the dwelling, or a reduction of the carbon dioxide emissions associated with energy use in the dwelling.

Visit our Dedicated PAS Website: www.compliantpas.co.uk

PAS 2035

With rising energy costs and the UK’s commitment to significantly reduce carbon emissions on the pathway to net zero, the demand for high-quality retrofit and renewable energy installations continues to grow. Government programmes delivered under the Warm Homes Plan aim to improve the energy efficiency of millions of homes across the UK, particularly those occupied by low-income or fuel-poor households.

These programmes are delivered in accordance with PAS 2035:2023, the UK’s specification for the energy retrofit of domestic buildings. PAS 2035 requires a whole-house approach to retrofit, ensuring that improvements such as insulation, ventilation, and renewable technologies are properly assessed, designed, installed, and monitored. Installers carrying out these measures must be certified to PAS 2030:2023 and registered under the TrustMark quality assurance framework.

Alongside energy-efficiency measures, the deployment of low-carbon heating technologies continues to grow. Funding programmes require installations to meet recognised industry standards and quality assurance processes.

Compliant Ltd provides a complete service to support businesses seeking certification and participation in government retrofit programmes. Our service is built around a proven PAS-compliant Quality Management System, enabling installers to meet scheme requirements, operate within the PAS 2035:2023 retrofit framework, and secure certification, allowing them to participate in funded retrofit programmes.

MCS

Becoming certified under the Microgeneration Certification Scheme (MCS) allows your business to demonstrate that it operates a robust and controlled installation process for renewable technologies such as heat pumps, solar PV, and battery storage. MCS certification provides assurance to customers, local authorities, and scheme administrators that installations are compliant, technically sound, and delivered with appropriate consumer protection.

For many domestic renewable installations, particularly those exporting electricity to the grid or installed through government funding, MCS certification is essential. For example, households wishing to receive payments through the Smart Export Guarantee must have systems installed by an MCS-certified installer. Likewise, low-carbon heating systems installed under schemes such as the Boiler Upgrade Scheme must be completed by an MCS-certified company to claim grant funding.

Compliant Ltd provides a complete service to support businesses seeking certification and participation in government retrofit programmes. Our service is built around a proven, MCS-compliant Quality Management System, enabling installers to meet scheme requirements, operate within the PAS 2035:2023 retrofit framework, and secure certification, allowing them to participate in funded retrofit programmes.

TrustMark, PAS 2035 and MCS: Understanding the Standards Behind Quality Home Retrofit in the UK

As the UK continues to improve the energy efficiency of homes and transition toward low-carbon heating, several key standards have been introduced to ensure work is carried out safely, professionally, and to a high standard.

Three of the most important frameworks in this space are TrustMark, PAS 2035, and MCS. These schemes work together to create a structured system for installing energy efficiency measures and renewable technologies in UK homes.

If you are planning a retrofit project, installing insulation, upgrading heating systems, or adding renewable technologies such as heat pumps or solar panels, understanding these standards will help you choose the right installers and ensure your project meets regulatory and quality requirements.

What Is TrustMark?

TrustMark is the UK Government-endorsed quality scheme for tradespeople working in and around residential properties. It provides a framework that helps ensure contractors meet strict standards for technical competence, customer service, and fair trading practices.

Businesses registered with TrustMark must be approved by recognised certification bodies and must follow defined industry standards. They are also subject to ongoing monitoring to ensure they continue to meet these requirements.

TrustMark plays a central role in the UK’s retrofit sector, acting as the consumer protection and oversight framework for many government-backed home improvement schemes.

For homeowners, this means working with a TrustMark-registered business offers greater reassurance that the installer has been independently assessed and operates to recognised industry standards.

How TrustMark, PAS 2035 and MCS Work Together

Although these schemes serve different purposes, they are closely linked and often required together for energy retrofit projects.

In simple terms:

· TrustMark provides the overarching consumer protection and quality assurance framework.

· PAS 2035 defines the process for planning and managing retrofit projects.

· PAS 2030 sets the installation standards for energy efficiency measures.

· MCS certifies renewable energy technologies and installers.

For many government-funded home energy improvement schemes, installers must be registered with TrustMark and comply with PAS standards. If renewable technologies such as heat pumps or solar panels are installed, the contractor must also hold MCS certification.

This layered approach ensures that projects are properly assessed, carefully designed, and installed by qualified professionals.

TrustMark, PAS 2035, and MCS form the foundation of quality assurance for energy-efficiency and renewable-energy installations in the UK.

Together, these frameworks ensure that retrofit projects are properly assessed, carefully designed, and installed by qualified professionals who meet strict industry standards.

For homeowners planning improvements such as insulation upgrades, heating replacements, or renewable energy installations, choosing contractors who adhere to these standards is one of the most effective ways to ensure a successful, reliable project.

What Is the Warm Homes Plan?

The Warm Homes Plan is a UK government initiative launched in January 2026 by the Department for Energy Security and Net Zero. Its main goal is to improve the energy efficiency of homes across the country, reduce household energy bills, and tackle fuel poverty.

The programme includes £15 billion in government investment and aims to upgrade up to 5 million homes by 2030 through insulation, heating improvements, and renewable energy technologies.

By improving the energy performance of homes, the government aims to:

· Reduce energy bills for households

· Lift up to 1 million families out of fuel poverty

· Improve comfort and health in homes

· Support the UK’s transition to low-carbon heating.

The UK has some of the oldest and least energy-efficient housing stock in Europe. Many homes still suffer from poor insulation, inefficient heating systems, and high energy costs.

The Warm Homes Plan was created to address these challenges by delivering large-scale upgrades that improve energy performance while reducing carbon emissions.

Government analysis suggests that upgrading homes through insulation, efficient heating systems and renewable technologies could significantly reduce household energy costs while improving long-term energy security.

The Warm Homes Plan represents one of the most ambitious efforts to improve the UK’s housing stock. With billions of pounds committed and millions of homes targeted for upgrades, it could significantly reduce energy bills, improve living conditions, and accelerate the transition to low-carbon heating.

For homeowners, landlords, and industry professionals, understanding how the Warm Homes Plan works — and how it connects with retrofit standards like PAS 2035 and MCS — will be essential as the programme expands over the coming years.

As the UK moves toward a more energy-efficient future, initiatives like the Warm Homes Plan are likely to play a central role in transforming how homes are heated, insulated, and powered.