What is PAS 2035: A Comprehensive Guide for Energy Efficiency Retrofit in Dwellings.

PAS 2035 is a critical standard in the pathway towards achieving net zero targets and decarbonising the built environment.
PAS 2035/2030:2023

The Goal of ECO4 and PAS 2035

The primary objective of ECO4 is to ensure that as many homes as possible achieve a minimum Energy Performance Certificate (EPC) rating of C. This initiative focuses on fuel-poor households, aiming to reduce emissions, support low-income and vulnerable individuals, and promote compliance with the fabric-first approach outlined in PAS 2035. Additionally, retrofit projects receiving government grant funding will be required to adhere to the PAS 2035 process starting from July 2021.

Shallow Retrofit vs Deep Whole-House Retrofit

One of the fundamental differences between ECO4 and PAS 2035 lies in the scope of retrofit projects. Historically, ECO has primarily involved large-scale single-measure shallow retrofit projects. These projects aim to achieve quick results within a limited budget, often without thorough assessments. On the other hand, PAS 2035 mandates a deep whole-house retrofit approach, which requires a comprehensive plan, specified outcomes, and a thorough assessment of the retrofit process.

The Challenges of PAS 2035

While the fabric-first approach outlined in PAS 2035 promotes long-term energy efficiency, it also introduces additional complexities and costs. Simple energy efficiency measures, such as upgrading loft insulation, can become more challenging and costly under the influence of PAS 2035. The specification requires extensive surveys, assessments, and coordination work, including potential physical ventilation upgrades. Consequently, a seemingly straightforward loft insulation job, costing around £800, could now require additional expenses of £2,000 or more for supporting assessments, coordination, and ventilation upgrades.

The introduction of such bureaucracy may impede the effective deployment of simple energy efficiency measures across the country, potentially hindering the race to achieve Net Zero by 2050. However, the PAS 2035 specification aims to account for and prevent unintended consequences by providing a set process for assessing the true impact of single upgrades on dwellings.

The Implications for Retrofit Projects

The contrasting approaches of ECO4 and PAS 2035 have implications for retrofit projects and the overall retrofit industry. While ECO4 offers a cost-cutting perspective that allows for shallow retrofits on a large scale, the introduction of PAS 2035 emphasizes the need for a more comprehensive and holistic approach. The fabric-first principle promoted by PAS 2035 ensures that retrofit projects consider the entire building envelope and prioritize energy efficiency measures that address the fabric of the building before focusing on technical systems.

The transition from ECO3 to ECO4 and the integration of PAS 2035 requirements may require retrofit professionals to adopt new methodologies, acquire additional skills, and collaborate with a wider range of stakeholders. This transition, although challenging, presents an opportunity to enhance the quality and effectiveness of retrofit projects, ultimately leading to improved energy efficiency and occupant comfort.

The Role of ECO4 in Achieving the Objectives of PAS 2035

While ECO4 and PAS 2035 have differing approaches, they are not necessarily mutually exclusive. ECO4 can evolve to support the deeper, whole-house retrofit approach required by PAS 2035. By aligning the objectives and methodologies of both initiatives, ECO4 can play a vital role in achieving the energy efficiency targets outlined in PAS 2035. The integration of ECO4 and PAS 2035 can create a comprehensive framework that addresses the needs of fuel-poor households, ensures compliance with energy efficiency standards, and accelerates progress towards a sustainable future.

The Benefits of Retrofitting

Despite the challenges and complexities associated with PAS 2035, retrofitting remains a crucial strategy for achieving energy efficiency and reducing emissions. Retrofit projects offer numerous benefits, including:

  1. Energy Savings: Retrofit measures can significantly reduce energy consumption, leading to lower utility bills and long-term cost savings.
  2. Improved Comfort: Retrofitting improves indoor thermal comfort by reducing drafts, improving insulation, and optimizing heating and cooling systems.
  3. Enhanced Health and Well-being: Retrofit projects can improve indoor air quality, reducing the risk of respiratory issues and creating a healthier living environment.
  4. Increased Property Value: Energy-efficient properties are in high demand, and retrofitting can enhance the market value and desirability of a property.
  5. Carbon Footprint Reduction: Retrofit projects contribute to the overall reduction of carbon emissions, playing a vital role in combating climate change.

Success Stories: Transforming Homes and Lives

The impact of retrofitting can be seen through numerous success stories. By embracing the fabric-first approach and implementing energy efficiency measures outlined in PAS 2035, homeowners have experienced transformative results. For example, the Smith family, living in an outdated and inefficient property, decided to undergo a deep whole-house retrofit. By improving insulation, upgrading heating systems, and optimizing energy usage, they achieved a significant reduction in their energy bills, improved indoor comfort, and enhanced the overall quality of their living environment.

Similarly, the Johnsons, a low-income family struggling with high energy costs, received support through ECO4 to retrofit their home. With the help of qualified retrofit coordinators and adherence to PAS 2035 guidelines, the Johnsons experienced a remarkable decrease in their energy consumption, allowing them to allocate their limited resources to other essential needs. These success stories highlight the transformative power of retrofitting and the positive impact it can have on households.

The Role of Qualified Retrofit Coordinators

To ensure the successful implementation of retrofit projects under PAS 2035, the role of qualified retrofit coordinators becomes crucial. Retrofit coordinators work closely with homeowners, contractors, and other stakeholders to oversee the entire retrofit process, from initial assessments to project completion. They ensure compliance with PAS 2035 specifications, coordinate the various aspects of the retrofit project, and monitor the progress and outcomes.

By engaging qualified retrofit coordinators, homeowners can have peace of mind knowing that their retrofit projects are being managed by professionals with the expertise and knowledge to navigate the complexities of PAS 2035. Retrofit coordinators act as trusted advisors, guiding homeowners through the retrofit journey and ensuring that the desired energy efficiency outcomes are achieved.


The introduction of ECO4 and the integration of PAS 2035 represent significant developments in the retrofit industry. While the transition may present challenges, it also offers opportunities to enhance the quality, effectiveness, and sustainability of retrofit projects. By aligning the objectives and methodologies of ECO4 and PAS 2035, stakeholders can work together to achieve energy efficiency targets, reduce emissions, and improve the lives of individuals and communities. Retrofitting remains a crucial strategy in the journey towards a more sustainable future, and with the right approach, the battle of red tape can be overcome, leading to transformative results for both homeowners and the environment.

To discuss your retrofit project or find out how we can assist you on your retrofit journey, please contact us.

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