Improving home energy efficiency - retrofit assessment review: policy report

Answers to Research Questions

1. What are the current options for consumers seeking assessment advice and information on clean heating and measures to improve energy efficiency for their home?

Level of agreement: Strong agreement that there are number of options with embedded limitations.

Strength of evidence: There are a variety of systematic assessment tools based on existing energy models (e.g., SAP and PHPP). There are a number of retrofit tools using these methodologies such as the Home Energy Model, PAS2035, and EnerPHit (see Annex 1 . However, many consumers will start with receiving a home energy check (based on RdSAP) or an EPC (also derived from RdSAP), which are of limited usefulness beyond recommending very basic measures and highlighting options for behaviour change, and so advisors and the Scottish Government should be doing more to be transparent and make consumers aware of these limitations. There was also a strong consensus that there has been enough discussion of these issues and not enough action.

2. To what extent do existing assessment methodologies provide a means of assessing the suitability of energy efficiency and heating measures in buildings?

Level of agreement: Very high agreement that existing assessment methodologies do not provide a robust and holistic means of assessing retrofit options as the assumptions made result in overly simplistic assessments.

Strength of evidence: The veracities of existing models and their capacity to handle multiple variables are questionable as, to greater or lesser extents, all methodologies use simplified variables and embedded assumptions. Influences such as location (e.g., the Borders vs Shetland, east coast vs west coast), exposure, and human behaviour are not dealt with effectively by any existing models, and may lead to unsuitable measures being recommended. In practice, the choice of any given assessment methodology or methodologies not prescribed by regulation becomes one of choosing the least-worst option(s) for the type of project – e.g., changing a heating system, tackling traditional buildings, a deep retrofit, planning a community-scale heating system, etc.

3. What are the limitations of these approaches (e.g. cost, time, specialist skills requirements)?

Level of agreement: Strong agreement on the existence and types of limitations.

Strength of evidence: There are limitations in the number of qualified assessors for any given assessment type, and their individual experience. There is a need for both more training provision across the retrofit landscape, for a higher level of training for assessors, and for training for assessors to avoid siloing them by the assessment method. For example, someone being trained to use the HEM should understand how it relates (or not) to other methods, in order to determine if it would be more appropriate to use an alternative method.

There is also a need to assess the suitability of potential candidates to avoid inexperienced assessors whose knowledge is wholly defined within the assessment tool they qualify in. There is also a common public perception that assessment processes are onerous and overly expensive, and a lack of awareness of the benefits of more holistic assessments, resulting in them favoring more limited assessments which may yield sub-optimal results. This lack of post installation and post occupancy assessments severely limits the verification of recommendations and projected savings which can be used to inform and improve the existing models.

Another significant limitation, which is causing confusion within the sector, is where retrofit recommendations made using those tools can be marketing tools for product suppliers - such as suppliers of heating technologies, insulation, and glazing options - without any limitations on the scope of measures being considered being made clear to service users. Common reasons for limitations on the scope and types of measures recommended by advisers or offered by installers include limiting them to those supported by government subsidies and loans, and advisors and installers having financial or other arrangements with manufacturers or suppliers.

4. Is the assessment of measures provided generic, archetypal, bespoke?

Level of agreement: Strong agreement that assessments are invariably generic, and of the various limitations of each option.

Strength of evidence: Assessment measures are invariably not bespoke and, through necessity of the simplification of variables embedded in the models used, were at best offering archetype-based recommendations and, in some cases, broad generic advice. There are exceptions - e.g., where owners are aware of the benefits of more holistic assessments and can pay for them – but even these can be limited by the choice of assessment(s).

Assessors who lack experience beyond undertaking assessments tend not to question the recommendations that their software packages generate. The ability to offer bespoke recommendations requires flexibility from the assessment methodologies, and so is dependent on the experience of the assessors. Assessors also need to be wholly independent from any of the suppliers of potential technology suppliers. This degree of independence is dependent on the regulation of the assessors.

Archetype-based approaches have some value – e.g. for shaving costs of community-scale retrofits of more homogeneous building types. However, their universality is questionable – e.g., where factors such as geography, exposure, and existing condition and maintenance are not considered.

There are also barriers to delivering the more holistic assessments needed for effective deep retrofits such as their costs, the costs of deep retrofits, an obstruction by tenants - e.g., due to the level of disruption and the (real or perceived) risk that costs will be passed on to tenants as rent increases.

5. Does the assessment process rely on occupants to report building characteristics or is a site visit by an assessor critical?

Level of agreement: Very high.

Strength of evidence: There was a very high, although not quite universal, consensus that, depending on the complexity of the project, at least one site visit by an assessor (and in some cases, a project manager or other professional) is critical. Occupants are not usually experts, and suitably qualified and experienced experts are able to pick up on issues, problems, and opportunities (etc.) that may be missed by occupants, as well as less qualified staff who have yet to develop what can be many years of tacit knowledge gained through experience. Examples of this included cold bridges, insulation quality, and structural issues. However, it should also be acknowledged that conversations between occupants and assessors can provide useful context and confirm details, and that this is more effective when these can happen as part of a site visit. The balance of evidence and views leads us to support the recommendation that site visits should be mandatory.

6. What are the costs associated with providing the assessment? Are there any instances where the service would be provided for free for the building occupant?

Level of agreement: Moderate.

Strength of evidence: There was little discussion of specific costs, or of what minimum or maximum costs should be seen as acceptable for any given occupant type(s). Rather, there was a general acceptance that some occupants should be supported more or less than others depending on their needs, financial circumstances, tenures, building types, etc.

7. Do existing assessment methodologies cover the suitability of multiple buildings or building parts to install a communal heating system?

Level of agreement: High to very high.

Strength of evidence: Very high agreement that, in general, the answer to this question is no. The main exceptions are PAS 2035 and 2038-based approaches, but even these have their limitations. Where the use of the more holistic assessments needed for this was reported, they were invariably extensions of existing methods (including PHPP and SAP, etc.), with varying degrees of success. Therefore, meeting this need is currently heavily dependent on an assessment provider being able to offer a bespoke approach and the (limited) geographical availability of suitable assessors. One suggestion was that BS 40104, if tailored appropriately, could form the basis of such a standard in the future. There is also a strong consensus that meeting this need is a highly complex task that can only be met by highly qualified and experienced professionals.

There was also a high level of agreement that existing methodologies offer very limited opportunities for such evaluations. The evidence strongly suggests that the current methodologies do not allow for systemic evaluation of suitability of multiple buildings or building parts to install a communal heating system. The limitations lie in siloisation of energy efficiency and heating strategies, with methodologies such as RdSAP, SAP, and PHPP not allowing for satisfactory assessments of fabric condition. Such methodologies are over-reliant on generic assumptions in the absence of detailed performance data (including performance in use), failure to address complexities such as shared infrastructure, energy management, scalability, and cost allocation, and neglecting critical system-specific factors like fuel sources and heat pump integration. Robust frameworks integrating detailed data, stakeholder engagement, and tailored strategies are essential to support delivery of communal heating projects across Scotland.

8. Do existing methodologies take a whole building perspective on the costs and benefits of fabric measures?

Level of agreement: Moderate – it was recognised that if interpreted correctly the existing methodologies can offer a whole building perspective on the costs and benefits of fabric measures. However local cost variations may not be sufficiently represented, and the results rely on the expertise of the assessor.

Strength of evidence: High agreement that existing assessment methodologies, such as SAP, RdSAP, and PHPP, lack a holistic framework for evaluating the costs and benefits of fabric measures, failing to account for user behaviour, regional cost variations, and long-term operational impacts. Energy Performance Certificates (EPCs) provide generalized cost estimates but are unsuitable for informed design decisions due to their reliance on assumption-based data.

Key factors such as ventilation, humidity control, and air quality are inadequately addressed to inform whole-building energy efficiency strategies, with limited consideration of air permeability, condensation risks, and material toxicity, which can significantly impact occupant health. Standards such as PAS 2035 and PAS 2038 emphasise a whole-building, fabric-first approach, but their effectiveness depends on assessor expertise and implementation quality. While RICS Retrofit Standard and BS 40104 provide some guidance, they lack detailed, comparable cost-benefit analyses - highlighting the need for more comprehensive, occupant-focused methodologies.

Note that, in hindsight, the wording of this question does not sufficiently clarify what is meant by “whole building”. However, most assessments used to guide retrofit projects (e.g., EPCs) are conducted for individual properties, such as flats in mixed-use and multiple-occupancy buildings. For energy efficiency measures, the impacts of the limitations of existing methodologies for assessing multiple-occupancy buildings are simply amplified in terms of assessing costs - i.e., not accounting for economies of scale for retrofitting properties at the same time. For communal and district heating systems, the impacts are the same as those noted under Objective 2 of this Policy Report and in Sections 3.17, 4.11, and 4.12 of the Technical Report.

9. Do existing methodologies allow for options to be compared – e.g. a comparison of the installation, operational emissions and running costs of improved building heat retention first with a low temperature heat pump, vs a high temperature solution without any insulation measures?

Level of agreement: Moderate. Although some respondents recognised that methodologies such as PAS2035, PAS2038, AECB, and Passivhaus / EnerPHit may allow for such evaluation, others observed this is rarely applied. Others felt that current methodologies are not designed or simply do not offer ability to compare cost and emissions to enable holistic decision-making.

Strength of evidence: Moderate. Insofar as existing retrofit assessment methodologies such as SAP, RdSAP, and PHPP are not designed for comparing detailed retrofit options. While these tools can theoretically be adapted for such analyses, the process is time-intensive, resource-dependent, and rarely used in practice due to its complexity and voluntary nature. These methodologies provide high-level insights but lack the detail needed for nuanced decisions, such as evaluating long-term emissions, running costs, or lifecycle impacts. Broad recommendations and limited attention to factors such as material properties, health implications, and net-zero planning further reduce their effectiveness. The need for advanced, accessible tools that integrate lifecycle costs and context-specific recommendations is critical for supporting comprehensive retrofit decision-making aligned with long-term environmental goals.

10. What gaps exist between current assessment methodologies and the methodologies required to deliver the stated scope for a HEETSA?

Level of agreement: High. Current methodologies fall short of the requirements of HEETSA, focusing on individual buildings, relying on predicted data, not accounting for occupant behaviour, dynamic performance modelling, whole lifecycle and projects often focus on regulatory baseline.

Strength of evidence: Conclusive evidence that current methodologies such as SAP, RdSAP, and PAS2035 fail to meet HEETSA’s goals. This is due to fragmented approaches, limited focus on whole-building strategies, non-comparable outcomes, and reliance on assessor expertise, all of which weaken their effectiveness.

Poor training and constrained accreditation models of retrofit professionals often lead to inadequate advice, poorly executed installations, customer dissatisfaction, and even non-mortgageable homes. The lack of post-occupancy evaluations hampers learning and improvement, while public confidence remains low due to negative experience and profit-driven advice.

Addressing these issues requires a tailored framework, better training standards, post-occupancy evaluations and customer-centred approaches recognising regional differences across Scotland. Industry collaboration, showcasing success stories and mission driven, resilience focused goals can allow to rebuild trust and demonstrate strong leadership from the Scottish Government.

11. For each source of advice and information on recommended clean heat and energy efficiency measures, what accreditation and qualifications exist to ensure that knowledge provided is accurate, relevant and to what degree it accounts for a building’s characteristics or circumstances of its location?

Level of agreement: Very high agreement that advice, often based on limited assessment types (e.g., RdSAP) rarely considers, or sufficiently considers, factors such as building characteristics, location, exposure, fabric condition, or other circumstances (including occupant circumstances). Also, very high agreement that such advice is often not delivered by suitably qualified staff; that the Scottish Government and service providers need to do more to make service users aware of these limitations; that training should include making advisors aware of the limitations of their knowledge; and that not doing so is resulting in non-optimal and (in some cases) negative and costly outcomes.

Strength of evidence: Very high. Many participants were able to cite examples of sub-standard advice leading to unsatisfactory or negative outcomes, commonly due to advisers and/or suppliers lacking sufficient knowledge and experience, and/or being limited or incentivised to promoting certain assessments, measures, or types of measures. This is particularly problematic for delivering clean heat, and even more so for community-scale and communal heating systems. It is not helped by the confusing, and changing, nature of the landscape for formal qualifications and accreditation, which is often driven by political expediency (e.g., for PAS 2035).

12. What code(s) of practice, professional memberships, quality assurance and independent/impartial scrutiny operates to support and regulate the activities of advisors?

Level of agreement: Moderate.

Strength of evidence: One problem here is that the word ‘advisor’ can cover anyone from a member of a community group, to a non-expert employed by an advice service, or an installer, through to a chartered professional regulated by their own institutional practices. It would, therefore, be unrealistic (and costly) to require all of these to fall under any given regulatory code or scrutiny body. Also, more reputable local installers (who often provide advice) voluntarily sign up to established schemes such as TrustMark, but are also partially regulated through word of mouth and customer reviews.

The question then becomes one of educating consumers about the different levels of authoritativeness of advice, and how to ensure all advisors are required to be scrutinised to a degree appropriate to the limits of their knowledge and experience, and carry appropriate professional indemnity insurance. Furthermore, TrustMark’s lack of emphasis on inspecting the quality of workmanship may be giving consumers a false sense of security.

However, as retrofit coordinators become increasingly common, there was a good degree of support for the suggestion of requiring them to adhere to an ethical code of conduct. This could become a simple form of regulation for those advisors whose knowledge and experience does not reach chartered or equivalent levels, help manage customer expectations, and rebuild trust.

13. Can advice on building fabric, clean heating and renewables all be provided by the same service?

Level of agreement: High.

Strength of evidence: The strength of the evidence here was probably stronger than the strength of agreement, due to experts and experienced professionals being more aware of the complexities of buildings and building systems, and being more aware of the limitations of their own knowledge and experience. There is also a supplementary question of whether such a single service would even be desirable, or how easy it would be to manage large numbers of staff with very different areas of expertise, whilst delivering and maintaining high quality outcomes. (Although outwith the scope of this report, there are parallels with other bodies whose performance has suffered due to mission creep).

Going deeper, it is also questionable whether a single service would be optimal for dealing with any of these three aspects. For example, there are many different types of building fabric and even authoritative bodies specialise in different types, so (for example) someone looking to retrofit a traditional building will be better served by advice from Historic Environment Scotland or a conservation architect, whereas someone looking to retrofit a modern building would likely be better served by advice from the Passivhaus Trust or an architect specialising in new builds. Another differentiation arises between professionals specialising in naturally passive buildings and those specialising in Passivhaus and equivalent builds incorporating MVHR.

Considering this, we note that one of the Scottish Government’s changes to EPCs will be to re-word “recommendations” to “potential improvement options”^[10]. This wording better reflects the limitations of EPCs, SAP, and RdSAP, and so could be adopted more widely by advisory services.

This also links to how the role(s) of retrofit coordinators could be more closely defined and how training for them could be better aligned. The option being that retrofit coordinators act largely in place of owners managing their own retrofit projects – understanding buildings’ and occupants’ needs and fast-tracking them to the best sources of more specialist advice before committing to any given measure(s).

14. Are the retrofit advice services provided independent/impartial of any associated supply chains for clean heating and energy efficiency measures installation services?

Level of agreement: Very high.

Strength of evidence: There were numerous examples cited of advice being limited by the availability (or not) of funding for any given type of measure, financial arrangements with manufacturers and installers, and the knowledge or awareness of advisors. These examples covered all services offering advice, including Home Energy Scotland, WarmWorks, local advice services, large and smaller installers, and even community groups. As such, this finding is not a criticism of any of these, but a simple statement of fact. It should also be acknowledged that, even where advice is independent of supply chains, policy, or other influences, there is still the potential for bias from professional experience of measures that have, or haven’t, worked in any given set of circumstances. Hence, even where advice is impartial, full surveys remain essential for ensuring optimal outcomes are delivered.

15. What would be the optimal environmental for delivery considering skills and qualifications, urban/rural access, professional practice (regulation, indemnity, complaints handling and redress), software integration and applications support?

Level of agreement: High, and very high amongst accredited professionals and learning specialists.

Strength of evidence: Strong agreement that there are substantial access barriers for certain types of learners – particularly adults who are earlier in their careers, those in rural and remote areas, and especially women and neurodivergent people. Strong agreement that consumer confidence is low and complaints to trading standards are rising due to issues such as spray foam installs and poor ASHP installations (etc). As regards renewable energy technologies, it is important to understand the differences between a system designer and an installer as these roles require different skillsets (notwithstanding that someone can be qualified to do both).

Also, strong agreement that the needs of adults and professionals are not being sufficiently understood or met due to an emphasis on pedagogy-based (as opposed to andragogy-based) learning opportunities, funding being invariably driven towards younger people (degree courses, apprenticeships, etc), and in-class and traditional learning (especially where such options are not accredited by professional associations). For adults, and particularly professionals, there is insufficient knowledge of professional practice and the types of learning they need and prefer, and the financial and time costs of doing so – e.g., meeting specific knowledge needs for different projects, and engaging in communities of practice. As such, care needs to be taken to ensure that regulation protects the needs of younger and early career individuals, whilst not creating barriers or disincentives for adults and professionals engaging in more targeted, needs-driven, and informal learning.

These problems also impact on indemnity, complaints handling, and redress insofar as how much due diligence a consumer can be expected to do when accessing advice and planning and delivering a retrofit project, should it go wrong and they need to seek redress. Similarly, there needs to be consideration of how much smaller, local installers should be expected to understand about retrofitting beyond the measure(s) they specialise in, especially given that, as they are often very trusted, they provide one valuable route for leveraging consumers towards more holistic retrofit projects. Similar questions and benefits also apply to community groups designing and delivering local retrofit projects.

However, as regards the often-generic advice provided by larger service providers, and particularly those using Scottish Government branding, there was a strong consensus that these should be more tightly overseen and required to have sufficient public indemnity insurance and clear routes to redress (should the Scottish Government decide they offer sufficient value for money, which was questioned). Not doing so was flagged as a risk to public trust in the retrofit agenda, and potentially the climate change and sustainability agendas more widely.

All these issues are exacerbated when it comes to traditional buildings, and to delivering clean heating technologies and communal and community heating projects (e.g., community-scale heat pumps and district heating). These require larger numbers of more qualified professionals and/or professionals with specific expertise (including non-technical expertise).

16. What barriers exist to the development and delivery of a technical suitability assessment service?

Level of agreement: Very high.

Strength of evidence: Strong agreement that the shortage of skilled professionals – assessors, surveyors, tradespeople, etc – is a significant barrier. For example, currently there are very few PAS2035/PAS2030 qualified people in Scotland, with similar shortages for assessing other standards (e.g., Passivhaus). This is partly due to funding being available in England where there has been 50% funding of retrofit assessor and retrofit coordinator courses. Retrofits require significantly more management input, which drives up costs, while the available trades barely suffice for new builds. This was highlighted during the Covid ‘home improvement bubble’, where householders often faced labour and materials shortages, and increased costs for both. However, whilst supply chains were affected, this was more symptomatic of existing skills and materials shortages rather than a temporary increase in demand.

Also, strong agreement regarding the dominance of new build and derogation of maintenance. Serving the new build market is less complex for tradespeople, and is more financially attractive due to economies of scale. Retrofitting is more complex, and requires additional management and customer engagement, and carries greater reputational risks (e.g., occupants of new builds will invariably blame problems on the developer). Maintenance has largely been overlooked in policy which, even under the ‘fabric first’ approach, tends to drive installing energy efficiency improvements rather than identifying and tackling fabric condition problems, which limit the effectiveness of energy efficiency measures and may mask underlying problems. This carries the risk of fabric problems becoming more serious and costly to address in the future, and increasing the likelihood that measures will need to be ripped out to address them.

Although with less agreement, there was also a concern that HEETSA could become an additional, potentially onerous, standard, particularly for local authorities and housing associations. This concern merits addressing through clear communication and engagement as plans move forward.

17. What opportunities exist to upskilling existing workforces to effectively deliver a technical suitability assessment?

Level of agreement: High, but stronger in some respects than others. This likely reflects the inherent bias in participants coming from built environment backgrounds.

Strength of evidence: Strong agreement that establishing clear, agreed-upon national occupational standards is critical to defining the required competencies for roles such as independent HEETSA assessors and retrofit coordinators. This will help professionals identify and fill skill gaps systematically. Also, strong agreement that retrofit jobs is a growing market, but less agreement over how rapidly the market can be expected to grow, and how long the market will last (i.e., how long until most buildings have been retrofitted to sufficient standards?). The main reason for this uncertainty being the gap between policy targets and the effectiveness of policies and support to deliver on them.

Opportunities exist to do more to engage with learning specialists who have moved into training and upskilling for retrofit and related professionals. At present, there are clear routes for young people through apprenticeships and further and higher education courses accredited by professional associations, although there is still a need for more students to take these courses, and the Scottish Government could do more to promote the benefits of taking them. However, beyond this, the market is emerging and much more fragmented, with a ‘wild west’ of ‘CPD certified’ training, which creates risks and unnecessary competition for newer and reputable providers. There was strong agreement that there is room, and need, for everyone, but the landscape is confusing, lacking in coordination, and having barriers to entry (i.e., costs and returns on investment). Furthermore, the skilled professionals and experts needed to support this growth are time-poor and will naturally tend to focus on their own career development, but they can and need to be engaged in the development of upskilling and training offerings.

As such, more needs to be done to engage with learning specialists, particularly as regards those specialising in adult and lifelong learning as adults represent significant untapped potential and a poorly served market. This covers adults from community groups with little prior knowledge and experience, through those in employment with transferrable skills seeking to transition into the market, to established professionals.

As regards established professionals, there is a need for the Scottish Government to better understand their learning needs and how they meet them, in order to support a more flexible and effective learning landscape. Chartered professionals benefit from the structured learning offerings provided as part of their memberships of professional associations, but experts and professionals (chartered or otherwise) often regularly engage in the targeted and more informal learning by attending seminars on specific subjects or technologies (etc), and by engaging in communities of practice, and more should be done to understand, support, and recognise the value of this (by employers as well as government).

There is no ‘one size fits all’ solution, but there are solutions that depend on factors such as the type of learner, their career stages, and their learning needs.