PAS 2035

In the retrofit standard framework PAS 2035 provides a specification for the energy retrofit of domestic buildings.

PAS 2035


It is evident that significant improvements need to be made within the energy efficiency of the UK’s building stock, if the country is to meet its global carbon commitments.

In 2015 the government commissioned the Each Home Counts review to identify and tackle the high level of failure present in domestic retrofit, and to determine a better process for the retrofit of energy efficiency and renewable energy measures. PAS 2035 (PAS 2035:2019 Specification for the energy retrofit of domestic buildings) was introduced as a result of this review, with the backing of industry and the government department for Business Energy and Industrial Strategy (BEIS). Following a transitionary period the government has proposed to make compliance with PAS 2035 mandatory for all public funded projects which would include ECO funded retrofit projects.


How is PAS 2035 different?


The PAS embraces quality retrofit work eliminating problems associated with defects, shallow retrofit, accountability, poor design and performance gap. PAS 2035 delivers a whole building approach to the retrofit process, considering the home, environment, occupancy and the suitable measures to install. This eliminates the issue of the retrofit work being considered in isolation which can unintentionally damage the overall building performance.


Where is PAS 2035 applied?


PAS 2035 and the retrofit standards framework may be applied to all domestic retrofit activity and embrace work that is initiated, procured, funded and delivered in a wide variety of ways including:


    • Programmes of retrofit promoted and/or funded by national or local government schemes
    • Programmes of retrofit initiated and/or funded by landlords, including social housing organizations, 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 form part of broader repairs, maintenance and improvement (RMI) activity related to individual buildings or building stocks.

What is the scope of the retrofit process?


The scope of the process includes:

    • Assessment of dwellings for retrofit.
    • Identification and evaluation of improvement options as part of the design process.
    • Monitoring and Evaluation of retrofit projects.

The measures and intent include:


    • Improvements to the insulation of the elements of the building fabric and reducing thermal bridging.
    • Improvements to building services.
    • Improvements to the air-tightness of the building envelope.
    • Establishing a safe dynamic moisture equilibrium through each element of the building fabric.
    • Improving the resistance of the building envelope to water penetration.
    • Providing metering and monitoring systems to promote the efficient use of energy.
    • Advising building occupants about improvement options appropriate to their homes.
    • Commissioning and handover of all of the above.

What is meant by a ‘fabric first’ approach?


Whatever the scale of retrofit, a ‘fabric first’ approach is encouraged as the most cost effective and technically sound. The five stages to this approach are: 1) Bring the building fabric into good repair, by dealing with defects that inhibit energy efficiency and compromise improvement measures such as water penetration, damp, structural defects and poor pointing masonry 2) Implement “low hanging fruit” measures that are low cost and easy to install, e.g. energy efficiency lighting, basic heating controls, better control settings 3) Improve the building fabric by means of insulation and air-tightness measures, and by minimising thermal bridging, in order to reduce heat losses and demand 4) Satisfy the remaining heat demand as efficiently as possible using efficient heating technology and responsive controls 5) Use LZC “renewable” energy technologies to reduce emissions further.


What are the different roles within the retrofit process?


Retrofit Advisor – Gives advice to a client or householder during the retrofit process, the evaluation of improvement options, the selection of improvement measures (EEM), the retrofit design, the operation and maintenance of installed measures, or how to operate a home in an energy efficient way after retrofit.

Retrofit Assessors – Retrofit Assessors are trained to undertake a retrofit assessment for dwellings in accordance with PAS 2035. The activities completed within the retrofit assessment include the production of an RdSAP assessment, a detailed floor plan, a condition report and an occupancy assessment.

The data collected from these sources is used by the Retrofit Coordinator to formulate a Medium-Term Improvement Plan. Accredited DEAs are well placed to become qualified Retrofit Assessors due to their extensive knowledge and experience with RdSAP methodology and assessment of existing dwellings.

Retrofit Coordinator – Retrofit Coordinators are required for all domestic retrofit projects in order to comply with PAS 2035. The Retrofit Coordinator occupies a vital project management role within the retrofit process and are needed to protect both the interest of clients and the public. They are responsible for overseeing a domestic retrofit project from inception to completion, and will liaise with building owners, and other retrofit project stakeholders in order to ensure effective project management. A Retrofit Coordinator can prepare a Medium-Term Improvement Plan using data from retrofit assessments, to provide a scope for improvement over a 20-30 year period.
Retrofit Designer – Package of information prepared by a Retrofit Designer that determines the unique combination of EEM systems, products, materials and their interrelationships, to be installed in a building in order to achieve specified energy efficiency and other outcomes for that building.

Retrofit Evaluators – Person qualified to monitor and evaluate the effectiveness of a retrofit project and provide feedback to the client / and or the project team.

Retrofit Installers – Person or organization undertaking the physical placement of an energy efficiency measure(s) in an existing building.

Greener Solutions Group provide a full package to include design, assessment, co-ordination to allow a turnkey solution for organisations undertaking Retrofit works under PAS 2035

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