Heat and Energy Efficiency Technical Suitability Assessment (HEETSA) Scoping Consultation – National Insulation Association response

Consultation Response – Heat and Energy Efficiency Technical Suitability Assessment (HEETSA) Scoping Consultation – National Insulation Association response

Closing Date: 29 August 2025
Response submitted by: National Insulation Association
For more information, please contact: info@nia-uk.org

About the National Insulation Association

The National Insulation Association (NIA) represents the insulation industry in Scotland and across the UK with a member base comprised of installers, system certificate holders, and manufacturers who provide a wide range of insulation solutions for homes and buildings. The NIA and its members are fully committed to maintaining and raising standards within the insulation industry.

Setting a standard for the retrofit assessment market that improves the quality of advice available to building owners will add confidence to building owners seeking advice. This should in turn encourage more building owners to invest in upgrades to their properties.

As the consultation notes, EPCs have a number of limitations which limit their usefulness as a tool for helping residents make informed decisions about the most suitable retrofit upgrades for their properties. EPCs are based on a simple, non-invasive assessment of a building that does not take into account occupancy or the unique features of a building. Moreover, the scoring methodology that underpins EPCs is based on assumptions about the impact of retrofit measures on a building rather than measured data showing the real impact of measures. As a result of these limitations, the findings and recommendations on EPCs are often inaccurate and generic. In response to a survey conducted by the National Retrofit Hub, 57% of respondents felt that they had little to no trust in the ratings and content of an EPC. The same research also found that contractors generally do not find EPCs useful for supporting their professional decision making, with 41% reporting they rarely or never use EPC recommendations for project planning or advising clients1.

Therefore, we welcome the Scottish Government’s proposals to develop a HEETSA which would provide a more detailed and building-specific assessment of a property than an EPC. This will give residents a more accurate picture of the true condition of their property and help

to inform them on the most suitable upgrades for their individual circumstances. By providing more reliable and property-specific information than EPC assessments, HEETSAs could also help to inform more targeted and effective policy interventions by the Scottish Government.

1 National Retrofit Hub (2024). What is needed from EPC reform to enable retrofit at scale? Available here.

The NIA believes that a HEETSA should cover the following elements:

• • Retrofit assessment
• • Retrofit design
• • Retrofit specification
• • Occupancy

Retrofit assessment

The HEETSA should cover retrofit assessment, involving an extensive survey of a building and its current condition. As the consultation suggests, this should include an evaluation of the current state of the building fabric. We believe that a whole-house approach to retrofit assessment and retrofit projects is the most effective approach, therefore it is important that it also includes a ventilation assessment, alongside any assessment of the building fabric.

We agree that this should include a detailed technical suitability assessment of potential retrofit measures, conducted by an appropriately qualified professional, to determine which interventions are technically feasible. The HEETSA should also evaluate any potential risks or barriers to retrofit measures, such as space constraints, enabling works, and the protected status of the building (if applicable). These risks must be carefully considering when recommending the most suitable measures for each property.

Retrofit design

We believe that a HEETSA should incorporate certain elements from the retrofit design stage within PAS 2035:2023. This will help to ensure that HEETSAs provide a suitable package of recommendations tailored to the individual needs of the building being assessed.

This should include a full cost-benefit analysis of the estimated impacts of different retrofit measures, similar to the improvement options evaluation within PAS 2035 retrofit design. This should cover the whole-life carbon, through-life cost, and potential health implications of individual measures. Residents can then use this information to make an informed decision on the most appropriate retrofit strategy for their home.

A medium-term improvement plan should also be carried out. This should take into account any risks or barriers to retrofit interventions and identify the best package of measures for improving the energy performance of a particular property. In line with the importance of a whole-house approach to retrofit, this should identify the best order for measures to be installed in and highlight any potential issues arising from the interactions between measures.

Retrofit specification

A HEETSA should consider the specification of measures. This is important to ensure that the proposed package of measures works together effectively and does not pose a risk to the property. While it would be the decision of the property owner whether or not they wish to proceed with certain measures, it is important that they are provided with detailed information on the most suitable measures and approach to installing them as part of a whole-house retrofit package. This will reduce the risk that building owners choose to install measures or packages of measures that may have unintended consequences for their properties.

Occupancy

We welcome the Scottish Government’s proposals to include occupancy within the scope of a HEETSA. Occupancy factors are important to consider when assessing the energy performance of a building and the most appropriate improvement measures. A full occupancy assessment helps to provide a more reliable picture of how a building performs and is used in the real-world. It is also critical to consider occupancy when assessing moisture and mould risk, as these can often be exacerbated by occupant behaviour. Considering occupancy and how it impacts upon these factors is vital to ensure that HEETSAs achieve their aim of providing a building-specific and occupant-centric assessment. It is also important that a HEETSA’s recommendations are tailored to the individual needs of the building and its occupants.

The NIA believes that the Government should accredit assessor organisations who in turn accredit assessors.

To ensure that the methodology used for a HEETSA is robust and fit for purpose, we believe that it should incorporate aspects from existing, government-approved methodologies. As the leading government- and industry-recognised framework for carrying out high-quality retrofit, HEETSA should build on existing elements of PAS 2035:2023. This includes detailed provisions for carrying out a thorough occupancy and retrofit assessment, as well as guidance on how to design and specify a suitable package of retrofit measures for an individual building.

However, we also recognise that a HEETSA may want to go beyond PAS in certain instances. In our view, HEETSA could incorporate elements of these other methodologies to help enhance the existing provisions within PAS 2035:

• • Scottish Building Standards – Technical Handbook
• • British Board of Agrement (BBA)
• • Reduced Standard Assessment Procedure (RdSAP) and Standard Assessment Procedure (SAP)

In addition to these existing methodologies, the HEETSA methodology should incorporate data on the in-use performance of energy efficiency measures. The use of pre-project use data is already collected in Wales and should be required within HEETSAs too. Using monitored data rather than the generic assumptions used in EPCs will allow HEETSAs to achieve a much more accurate picture of a building’s in-use performance than is possible with an EPC. This will in turn help to support more targeted and effective recommendations and interventions.

When it comes to individual factors within a building, we believe that a HEETSA should consider the following:

• • building fabric and performance, including insulation levels and thickness,
• • airtightness,
• • thermal bridging,
• • glazing,
• • ventilation,
• • heat loss calculations prior to retrofit installations
• • construction and condition of the building
• • age and type of building (solid wall, cavity, timber frame),
• • structural integrity,
• • damp,
• • heritage constraints,
• • location and external factors,
• • local climate (e.g., Scottish Highlands vs. southern England),
• • grid capacity,
• • space for external units,
• • noise constraints,
• • planning rules,
• • occupant needs and usage patterns,
• • vulnerable occupants (e.g., elderly, fuel-poor)

The NIA believes that the Scottish Government should procuring and develop methodologies for HEETSAs. However, we also think that the market has a role to play in helping to fill gaps within existing methodologies.

HEETSA assessors should draw on existing qualifications, such as Domestic Energy Assessment and PAS 2035 roles, but add additional elements and accreditations where more specialist skillsets are required.

We believe that it is feasible for an individual assessor to have the sufficient skills and knowledge to complete a HEETSA, however as mentioned in our response to Question 6, they may require some additional accreditation and training.

The NIA strongly agrees that non-personal data gathered through a HEETSA should be stored to form a building logbook or green building passport. A 2024 report on EPC reform published by the National Retrofit highlighted the need for EPC data to be more accessible to the retrofit industry, landlords, homeowners and service providers2. Keeping track of this information through a building logbook will provide residents, industry and government with a wealth of data on the historic condition of buildings, as well as a guide for future improvements. This could be used to underpin a number of policy interventions. We agree that data gathered via a HEETSA should be stored in green building passports, as a reliable source of granular data on the condition of a building.

2 National Retrofit Hub (2024). What is needed from EPC reform to enable retrofit at scale? Available here.

The NIA strongly agrees that the HEETSA assessor should be required to be independent of the outcome of the assessment.

The NIA believes that the results of a HEETSA should be made available to inform the production of a revised EPC and should be considered acceptable “documentary evidence” to override default values.

As noted in our response to Question 1, there are a number of issues with EPCs which limit their accuracy. In-depth research conducted by Leeds Beckett University between 2008 and 2016 showed that at least 27% of all EPCs lodged between 2008 and 2016 had a discrepancy that suggests an error was made (3). Therefore, if a more detailed and reliable HEETSA assessment has been carried out, we believe that this data should be able to override default EPC values, which are often inaccurate, We don’t think HEETSA findings should automatically result in the production of a revised EPC, as there may be instances where this is not suitable. However, we generally believe that an EPC should be based on the best data available at the time, which is likely to be a HEETSA if this has been carried out.

3 Hardy, ALR and Glew, D. 2019. An analysis of errors in the Energy Performance certificate database. Available here.

a) The NIA strongly agrees that a HEETSA should result in a standardised certificate or report. Standardisation is important so that property owners and occupants can easily compare the performance of their building against others. This will also make a HEETSA’s findings more accessible and easier to understand for residents, hence helping them to make more informed decisions about future upgrades to their properties.

b) We believe that the following information should be included within the HEETSA report or certificate:

• Current state of the building fabric, including insulation and ventilation.
• Recommended energy efficiency and ventilation measures, with suitable justifications.

We believe that HEETSAs should be optional for those building owners or occupants who wish to find out more detailed information about their building and possible energy performance improvements. However, we do not think HEETSAs should be a mandatory requirement.

No, given that HEETSAs are currently intended as an optional further assessment, we do not think it is necessary to develop a legal basis for them at this time.