New standards in retrofit: PAS 2035

Retrofitting of UK homes to improve energy efficiency is blighted by poorly planned and executed projects, so a new BSI standard is seeking to ensure significant improvement


  • Prof. John Edwards

27 September 2019

Climate change and its devastating effects have led to a greater emphasis on energy efficiency in the built environment. Ensuring homes are energy efficient plays a significant part in this. Making existing homes more energy efficient is important, but there are many examples of poorly designed and implemented retrofit work that has had unintended consequences from encouraging mould and condensation to increased fire risk. Some retrofit work has actually made buildings less sustainable and, in some cases, less energy-efficient, generating more carbon than has been saved. A more informed and professional approach is therefore necessary.

On 18 June, the British Standards Institution (BSI) published PAS 2035: 2019 Retrofitting Dwellings for Improved Energy Efficiency – Specification and Guidance for homes of all types and ages. This is a response to Each Home Counts, an independent review of consumer advice, protection, standards and enforcement for UK home energy efficiency and renewable energy measures published in December 2016, which contains 27 recommendations. supported by an industry code of conduct, a consumer charter, and a framework of technical standards for retrofit; the first of these has since been established in the form of the government-endorsed TrustMark quality scheme.

PAS 2035 is the overarching document in the retrofit standards framework, with which users of the TrustMark scheme will be required to comply when carrying out work on dwellings. All other standards referred to in PAS 2035 are part of the framework, and users of the TrustMark scheme must also comply with those as appropriate. It is expected that PAS 2035 will be applied to retrofit projects outside the quality assurance framework as well, where public finance is involved. PAS 2035 is a requirement under the Energy Company Obligation (ECO).

PAS 2035 sets out a requirement for the proper assessment of dwellings and design and implementation of retrofits, and relates to PAS 2030: 2019 Specification for the Installation of Energy Efficiency Measures (EEM), in existing dwellings and insulation in residential park homes published on 17 June this year, which is the specification for installers to follow when selecting materials, components and methods of installation.

One key aspect of PAS 2035 is that it requires a whole-house approach. Not everything in a home has to be addressed, but the planned retrofit must take account of the house in its entirety, reducing the risk of inadvertently installing measures that have a negative impact on others and on the building generally. The whole-house approach is principally risk-based; projects are categorised in one of three groups as determined by a risk matrix.

Retrofit roles

PAS 2035 is unusual in that it splits the fulfilment of the specification's requirements by particular roles (see Table 1). Individuals in these positions must undertake training, possess qualifications and be members of professional institutions according to their role and the type of building being retrofitted.

The key role is the retrofit coordinator, often described as a project manager with expertise in retrofitting buildings, who is responsible for overseeing the activities of the retrofit adviser, retrofit assessor, retrofit designer, retrofit evaluator and retrofit installer. This is a broad role, with tasks ranging from working out the technical risks to advising on listed building consent. The varied tasks mean the coordinator is well placed to undertake other roles as necessary. They are required to obtain a level 5 professional diploma in domestic retrofit coordination and risk management, training for which is available from the Retrofit Academy.

"PAS 2035 requires a proper assessment of a building, and a considered proposal and specification of works"

The retrofit assessor will either be a qualified retrofit coordinator or a qualified domestic energy assessor, and must also hold a Construction Industry Training Board level 3 award in the energy efficiency and retrofit of traditional buildings, assuming they are working on such a property. This is an established qualification in retrofit independently accredited by the Scottish Qualifications Authority, with training from the Environment Study Centre.

The role of the retrofit designer is more complex. In cases of the lowest risk, where a single retrofit measure is being installed, a manufacturer-approved designer can fulfil the role; for other low-risk projects, a retrofit coordinator or a qualified architectural technologist is required. For higher risks, professionally qualified designers who are members of a professional institution, such as RICS, are necessary. Where the highest risk category is concerned and the building is traditionally built, the designer will also need to be a member of a building conservation competency scheme such as the RICS Building Conservation Accreditation Scheme.

Pros and cons

On the whole, PAS 2035 should help significantly improve the way UK homes are retrofitted by requiring a proper assessment of a building, and a considered proposal and specification of what works should be carried out. However, with more than 50 individuals in the PAS 2035 steering group, it is no surprise that some are not fully satisfied with the end product.

Some view PAS 2035 as a wasted opportunity, thinking that it could take a more holistic approach to the energy efficiency of homes. They believe it focuses solely on retrofitting measuresand neglects to address the positive impact that appropriate maintenance, repair and improvement of existing, core building fabric can have, although the value of maintenance and repair is mentioned in the side notes.

It has some very specific technical requirements in relation to ventilation and the calculation of energy loss, for example, but many of these are optional, which may seem as though it offers professionals a way of avoiding compliance. In reality, these requirements mean that those involved in projects can make measured judgements. In the case of traditional buildings this is a huge advantage, as a risk-based approach is often the only feasible way forward.

There is also debate about whether PAS 2035's acknowledgement that different building types, particularly traditional buildings, require different skill sets is a positive thing. This debate may show the UK construction industry does not understand the differences between buildings of different ages. The retrofit coordinator role and training provision have also received a mixed response.

The retrofitting of buildings needs to be improved, as is seen from examples such as the Grenfell Tower tragedy, and the failure of an external insulation contract in Preston that has resulted in 300 homes remaining uninhabited. PAS 2035 aims to set detailed requirements for building pathology, thermal modelling and calculations, ventilation, interactions between energy-efficiency measures, testing, commissioning, monitoring and evaluation, and obliges individuals holding particular roles to have specific qualifications and membership where relevant.

As with any standard or specification, time will tell how effective PAS 2035 is; however, a review has already been scheduled for 18 months' time to ensure that it achieves its goal of improving the energy efficiency of UK homes with better retrofitting practices.



Related competencies include: Housing maintenance repair and improvements, Sustainability

Further information: The Retrofit Academy offers retrofit coordinator training. The Environment Study Centre provides advice and events on retrofit and qualifications in retrofitting traditional buildings.

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