Retrofitting of Traditional Buildings

GN2019/5, September 2019

This is one of a series of occasional Guidance Notes published by The Institute of Historic Building Conservation (IHBC) and an updated version of one published in June 2019. IHBC Guidance Notes offer current and recent​ ​​guidance into topics that we consider crucial to the promotion of good built and historic environment conservation policy and practice. The Notes necessarily reflect knowledge an​d​ practice at the time they were developed​, while the IHBC always welcomes new case examples, feedback and comment to for future revisions and updates.

1. Buildings are and will continue to be under pressure to be made more energy efficient and whilst this is sensible, experience to date suggests that risks of unintended consequences are common.

2. This guidance intends to provide an outline on the most appropriate approach, which is a holistic one. It also provides comment on competencies and new publications by the British Standards Institution (BSI) on retrofit.

3. Note that this guidance applies to traditional buildings with and without statutory protection as well as modern buildings with statutory protection to a limited degree.

4. For more on the legislative and policy context, and sources of advice, see the IHBC’s Guidance Note on Climate Change and Older Buildings – key sources

General Approach
5. The approach is as generally outlined in BS 7913: 2013: Guide to the conservation of historic buildings.(1) This means that individuals must be sufficiently competent in what they do.

6. It is essential that those involved understand that retrofitting is not the first thing to think of when considering how to make a building more energy efficient. First of all try and get the original building fabric to perform as the best it can with appropriate maintenance and repair as well as providing it with appropriate use. After which, it is essential to start with the easy things first and then work up to those things which are more difficult and costly. The overall approach is described in the articleEnergy efficiency of traditional building published in 2016. (2)

7. The approach to retrofitting traditional and historic buildings up to the design stage was described in the special ‘green’ edition of Context (3), which also contains a number of useful articles on the subject. Here the stages are described in the form of guidance and are also taken up to the implementation, post occupancy evaluation and auditing which is part of a quality management process.


IHBC Retrofit Process up to pre-specification stage
IHBC Retrofit Process up to pre-specification stage

8. Undertake a condition survey that especially focuses on any issues with moisture.(4) A building pathological approach shall be taken that searches for the cause of problems. Include issues concerning the healthy occupancy of the building.

9. Assess the use of the building and if it is a dwelling note the number of occupants. Assess the moisture produced from the activities noted and compare to the normal activities and the moisture produced from them.

10. Undertake an energy efficiency assessment using RdSAP. (for dwellings) (5)

11. From 8 and 9 above assess activities required that will make improvements to energy efficiency and healthy occupancy and conclude with a list of recommendations (e.g. repairs, use issues).

12. List the works required from RdSAP (for dwellings).

13. Consider the recommendations from RdSAP by way of the STBA (6) retrofit guidance wheel and conclude with a list of works and retrofit measures.

14. With the conclusions from 13 above, carry out a cost benefit analysis with the concluded recommendations. This process shall be holistic but also consider information on both payback and realistic life expectancy of the measures and works.

15. Assess significance and undertake heritage impact assessments (HIA’s) (as detailed in BS 7913: 2013) to measure the impact of the proposals from 14 above and develop means of mitigation. This process to include the noting of other alternatives and detailing why they were rejected.

16. If the concluded works and measures from 15 above are altered, then HIA’s shall be repeated until a satisfactory outcome can be achieved.

17. Undertake a specification non-compliance risk assessment and determine means of mitigating risks as described in BS 7913. High / medium risks – mitigate through membership schemes (e.g. Trustmark) or ‘risk management’ ensuring that the means of subsequent quality auditing is considered at this stage.

18. Design works and measures incorporating risk management requirements as necessary. A useful article is Managing Risks in Building Conservation Projects . (7)

19. Works and measures implemented, and risk management methodology adopted throughout as necessary through to completion.

20. Post occupancy evaluation.

21. Audit scheme specification compliance as noted in 17.

BSI Publications PAS 2030 and PAS 2035 (8) – to be noted
22. PAS 2035: 2019: Retrofitting dwellings for improved energy efficiency – Specification and guidance is the overarching standard specification for retrofitting dwellings of all types and ages. It is a product of the Each Home Counts review and has been prepared to guide all government-supported projects including those under the Energy Company Obligation (ECO 3 until 2022). PAS 2035 does not take a totally holistic approach, in that its scope is on retrofit and not the other means by which to make homes more energy efficiency. This makes it difficult to follow the ‘stages’ described above and therefore the recommendations of the IHBC in this guidance document.

23. Retrofitting traditional buildings needs to be risk based. PAS 2035 is not totally risk based but provides the option of taking a totally risk based approach.

24. In PAS 2035 risks are based upon a risk matrix.

25. PAS 2030: 2019 Specification for the installation of energy efficiency measures (EEM) in existing dwellings and insulation in residential park homes is implemented alongside PAS 2035 and it is a requirement for Retrofit Installers to follow.

26. There is a requirement to follow BS 7913: 2013 in PAS 20352035 in some circumstances.

27. PAS 2035 stipulates several roles each with particular requirements in terms of memberships, training and qualifications. These are self-evident within the PAS.

28. PAS 2035 nevertheless contains useful details and sets out training, qualification and membership requirements which are not perfect, but sets out a benchmark, which provides guidance on the minimum requirements which should be ideally adopted for all retrofit. However, there is no specific requirement for training in the use of BS7913:2013 or in dealing with traditional buildings, unless a building has special protection and only for some roles – see 29 below.

Qualifications and Competencies
29. There is only one qualification in the energy efficiency and retrofit of traditional buildings the SQA Level 3 Award in the energy efficiency and retrofit of traditional buildings. Whilst it is a requirement under PAS 2035 for Retrofit Assessors and Retrofit Evaluators, this is only in respect of buildings with special protection. The IHBC considers that all such training should be a requirement for all roles in respect of retrofitting all traditional buildings. This training involves technical issues, heritage values and levels of significance as well as heritage impact assessments.

30. PAS 2035 requires designers to be members of a conservation competency scheme and, for the sake of robustness, this requirement should be observed outside PAS 2035. This means that designers of retrofit work shall be a member of a conservation competency scheme and where the building is protected the category of membership shall be at the highest level.

Building Regulations/Standards
31. Improvements will often be necessary as a consequence of preceding planned works, known as ‘consequential improvements’. In England details can be found in Approved Document Part L1b section 6, in Wales Part L1b section 5 in Scotland section 6.2.8 of Building Standards Technical Handbook Domestic Energy and in Northern Ireland Technical Booklet F1 paragraph 41. Whilst each country is slightly different, concessions can be granted not to undertake certain work even for non-designated traditional buildings where it is not technically feasible or effects character. It is vitally important to seek concessions where necessary.

Further Guidance and Information
32. There are other more detailed publications on energy efficiency and retrofitting of traditional buildings produced by heritage bodies and others. It is important to note that regardless of the general ingredients in such documents, it is essential to understand that in their application technical issues, the use of buildings and heritage values must all be considered, which would then satisfy BS7913: 2013.

Professor John Edwards MA, DipBldgCons, BCAS, CEnv, FCIOB, FRICS, IHBC


1. BS 7913: Guide to the conservation of historic buildings

2. Energy efficiency of traditional buildings

3. Context 149

4. Context 149

5. A reduced data version of Standard Assessment Procedure (SAP), RdSAP, is used for existing dwellings.

6. Sustainable Traditional Buildings Alliance (STBA)

7. Managing Risks in Building Conservation Projects

8. Publicly Accessible Specifications (PAS)

9. SQA CITB National Construction College and Environment Study Centre

© 2015 Registered as a Charity No1061593 Company Limited by Guarantee Registered in England No 3333780.
Registered as a Charity in Scotland: No. SC041945. Registered Office: 3, Stafford Road, Tunbridge Wells, Kent. TN2 4QZ Contact us