What are the principles of PAS 2035?

What are the principles of PAS 2035?

By Sophie Neaves on Fri 14 June 2024

What are the principles of PAS 2035?

PAS 2035 is a crucial standard for retrofitting homes, ensuring quality, safety, and energy efficiency. This blog outlines its main principles and impacts on retrofit projects. For more details on PAS 2035 ventilation requirements, take a look at our guide.

Main principles of PAS 2035

PAS 2035 is a framework for project delivery (not a new BSI Standard) for an energy retrofit on an existing domestic building. It aims to raise standards through a ‘whole house’ approach and focuses on key principles to ensure effective and safe retrofits, making sure they’re sustainable for years to come. Here we delve into those principles in more detail.

Professional accountability

This principle outlines that qualified professionals should oversee retrofit projects, ensuring accountability and adherence to standards - whether it’s a success or a failure. Retrofit coordinators, assessors, and designers must have appropriate qualifications and accreditations. This ensures that every step of the process, from assessment to installation, is managed by knowledgeable experts, minimising errors and ensuring high-quality outcomes.

Whole house approach to retrofit

This approach considers the entire building, ensuring all systems work together for optimal energy efficiency and comfort. This principle doesn’t just look at the individual elements, but emphasises how all building elements connect, meaning that improvements in one area do not negatively impact another. It promotes a holistic view, considering insulation, ventilation, heating, and structural integrity together to create a cohesive and efficient retrofit plan.

Bespoke projects

Each retrofit project is carefully designed to address the unique characteristics and requirements of the building and the people living in it. This is achieved by conducting thorough assessments and creating a customised plan that avoids a one-size-fits-all approach. This approach ensures that the solutions implemented are suitable and effective, enhancing the building's performance and comfort while meeting the occupants' needs.


Emphasis is placed on using high-quality materials and skilled workmanship to guarantee the longevity and effectiveness of the retrofit measures. This includes adhering to rigorous standards, quality assurance processes, inspections, and testing to ensure that the retrofits deliver the expected energy savings and improvements in building performance. 

Build tight, ventilate right

The principles focus on sealing the building envelope to prevent energy loss while ensuring proper ventilation to maintain indoor air quality. This involves finding the right balance between airtightness and adequate ventilation to prevent issues like dampness and poor air quality. Mechanical ventilation systems that provide fresh air while recovering heat are often recommended to optimise both energy efficiency and occupant health.

Fabric first retrofit

Priority is given to improving the building's fabric, such as insulation and windows, before installing new systems or technologies. This approach enhances the thermal performance of the building's outer layer, reducing energy demand and creating a stable indoor environment. By focusing on the fabric first, subsequent installations, such as heating systems, can be more efficient and effective, leading to long-term energy savings.

Top impacts of PAS 2035

PAS 2035 introduces several significant impacts:

  • New roles with qualifications and accreditations required: The standard mandates specific qualifications for roles such as retrofit coordinators and assessors, ensuring professionals overseeing projects are adequately trained and accredited.
  • Deep assessment: Unlike routine Energy Performance Certificate (EPC) assessments, PAS 2035 requires comprehensive data collection using full Standard Assessment Procedure (SAP) or Passive House Planning Package (PHPP) methodologies, feeding this data to the retrofit coordinator for informed decision-making.
  • Risk assessment: A measures matrix is used to assess and manage risks, informing the triage process and ensuring appropriate retrofit measures are selected.
  • Medium-term retrofit plans: Providing a clear roadmap for ongoing enhancements and anticipated improvements. These plans outline future steps and offer a strategic approach to achieving long-term objectives.
  • Design input by specialists: Incorporating input from specialists where necessary, means installation and integration of retrofit measures run smoothly. Their expertise helps make sure the implemented solutions are effectively coordinated and optimised for the specific project requirements.
  • Handover to include how owner/tenants get best outcomes: Detailed handover processes allow owners and tenants the opportunity to better understand how to operate and maintain new systems properly. When detailed guidance is provided, they’re then empowered to maximise the benefits of the retrofit and achieve the best possible outcomes.
  • Monitoring and evaluation: Continuous monitoring and evaluation enables retrofits to perform as intended. They facilitate the long-term effectiveness of the implemented measures, ensuring that the desired energy savings and improvements are realised over time.

Why use PAS 2035 in your retrofit projects?

As a social landlord or housing developer, following the PAS 2035 guidelines for your retrofit projects can offer significant advantages. By adhering to this approach you increase the chances of achieving the desired improvements you've invested in, while also safeguarding your housing stock from unsuitable retrofit solutions that could compromise their condition.


PAS 2035 provides the opportunity for you to develop a forward-thinking investment strategy that considers future needs, making sure that your properties remain resilient and adaptable over time. Plus,  it provides a structured framework for collaborating effectively with suppliers and contractors, helping you get the best value for your money while minimising disruptions and rework.


Throughout the project's various stages, professional oversight is ensured, promoting quality control and accountability. Enhancing your understanding of PAS 2035 and integrating it into your planning and management approach is crucial. This could potentially qualify you for the role of Retrofit Coordinator. Familiarising yourself with the accreditation requirements for your supply chain under the TrustMark scheme is also essential for a smooth retrofit process.


By following PAS 2035, you can optimise your investment, mitigate risks, and ensure a well-coordinated retrofit project that delivers lasting benefits for your housing portfolio and the occupants.


How Airflow can help

Airflow offers trusted expertise and product solutions to ensure compliance with PAS 2035, particularly the "build tight, ventilate right" principle. Whether you need to evaluate the adequacy of an existing ventilation system or undertake a comprehensive overhaul, our trusted expertise is readily available to support you.

We take pride in making sure that every project we work on exceeds the required standards, going above and beyond to equip your properties with high-performing, energy-efficient ventilation systems. Our commitment to excellence means that you can rely on us to provide reliable solutions that not only work within PAS 2035 but also contribute to creating healthier, more comfortable living environments.


Discover how we can assist you in adhering to PAS 2035 with efficient ventilation systems in your properties. Explore our range of products, take a look at our selection software on or reach out to our team today. Our knowledgeable experts are eager to partner with you, understanding your unique needs, and delivering tailored ventilation solutions that drive compliance and enhance the overall quality of your housing portfolio.