Domestic and non-domestic energy performance certificates: review

5. Identification of Issues, Workshops and Additional Modelling

5.1 Identification of topics and technical issues

In Section 4, the thematic analysis identified four overarching topic areas that crossed over multiple broad themes and keywords. A fifth overarching topic, i.e. non-domestic buildings, was added here to these four: the relatively few responses concerned specifically with non-domestic building issues meant they were obscured by domestic building concerns, although non-domestic building concerns also crossed over multiple broad themes and keywords.

Along with these overarching topics, a number of more technical issues also emerged.

These were reduced to four specific issues here, as one of technical issues was outside the scope of this review (i.e. decarbonisation) and several technical issues became subsumed within the overarching topics (i.e. benchmarking, new technologies, electric heating). Two technical issues (i.e. rooms in the roof, and measuring windows) were added based on the authors’ experience. The 5 overarching topics and 4 specific technical issues are presented graphically in Figure 5.1.1 below.

Figure 5.1.1: Overarching Topics and Technical issues

Each of these overarching topics and technical issues are explored in more detail in this section with regard to identifying specific concerns within them.

5.2 Traditional buildings

5.2.1 What is traditional?

It would appear many people have a view on what is a ‘traditional’ building, and that these views encompass a wide diversity of opinions and constructions. The thematic analysis categorised 85 responses from within the ‘built form’ theme as pertaining to traditional buildings^[45], by combining the contributions described as ‘traditional’, ‘older’ and ‘pre-1919’ (see Table 5.2.1)

Table 5.2.1: Frequency analysis of descriptors within ‘Built Form’ theme

Broad theme: Built Form	Number of contributions
traditional	72
older	12
rooms in roof	8
non-traditional	4
hard to treat	3
Scottish housing stock	2
size	1
whole building	1
pre-1919	1
pre-1940	1
masonry	1
Total	106

5.2.2 Identifying the Issues

The starting point for examining the issue of traditional buildings within SAP, RdSAP and SBEM calculation methodologies and the production of EPCs is a public perception that the process is not attuned to the needs of traditional dwellings: for example;

“The EPC is not sensitive to the nature of these houses and imposes one standard across all areas and housing types”.^[46]

This public perception is evident when the traditional building responses are examined in more detail.

The nature of many of the comments revolve around the methodologies not taking into account some aspect of a traditional building sufficiently in the calculation, for example, the use of default data results in inaccurate results and inappropriate recommendations on the EPC. However, some of the comments conflate a number of issues: it is not that SAP, RdSAP or SBEM did not take account of the nature of traditional buildings but that the respondent was unhappy with the results or the improvement recommendations, or that they considered they had done everything to improve their property and it still did not comply with the proposed minimum SAP (energy efficiency) standard, for example;

“We spent in excess of £20,000 fully insulating a traditional granite 1.5 story farmhouse with environmentally friendly products (wool insulation & Icynene) and installed a wood burning stove with back boiler for radiators and oil back up boiler (no mains gas, wood pellets not viable, electricity supply not reliable enough to install air source heat pump) at further cost and achieved a low E in the EPC. There is obviously a huge glitch in the software calculation"^[47]

These issues need to be disentangled to discern the actions that would enhance EPCs in Scotland as we go forward.

The 85 responses pertaining to ‘traditional buildings’ were spread across 18 keywords, with almost a complete overlap with the methodology and modelling broad themes (see Table 5.2.2 below). Cross-referencing the keywords against the methodology and modelling broad themes identifies the more specific nature of the concerns. The three most common issues were:

• the use of default values in the calculation and assessment of SAP, RdSAP and SBEM and their reporting on the EPCs;
• the reporting of the results and recommendations on the EPC which are the determined within RdSAP by Appendix T of the SAP methodology; and,
• the accuracy of the results produced for traditional buildings.

Overwhelmingly, the responses on traditional buildings came from the private rented sector consultation.

These ‘traditional building’ concerns fall across several of the overarching topics.

Table 5.2.2: Frequency of traditional building contributions broken down by Methodology and Modelling themes

Keyword	Broad theme: Methodology							Broad theme: Modelling
	Appendix T (n=31)	Metric (n=20)	Defaults (n=17)	PCDB (n=4)	Thermal mass (n=3)	New tech. (n=2)	Not classified [48](n=8)	Defaults (n=32)	Accuracy (n=25)	U-values (n=7)	Metric (n=4)	Min standards (n=3)	Thermal mass (n=3)	Real data (n=1)	Not classified (n=10)
recommendations (n=28)	22	1		3		2		21	5			1			1
traditional buildings (n=24)	2	9	11	1	1			3	10	7	1		1	1	1
surveyor skills (n=14)	5	1					8	4	2						8
performance gap (n=8)		5	3						8
metric (n=3)		3									3
minimum standards (n=2)	2							1				1
thermal mass (n=2)					2								2
benchmarking (n=1)		1										1
conventions (n=1)			1					1
ventilation (n=1)			1					1
windows (n=1)			1					1
Total	31	20	17	4	3	2	8[49]

5.3 EPC reporting and recommendations

5.3.1 Current Scottish Domestic Sector EPC Format

The Scottish domestic sector^[50] EPC presents an energy performance assessment of a property in terms of its energy efficiency rating (i.e. the SAP score and its banding) (see Figure 5.3.1) and its environmental impact rating (see Figure 5.3.2).

Figure 5.3.1 – The Energy Efficiency Rating graphic showing the A-G banding with their respective range of SAP scores, the current SAP score and banding of the property assessed, and its potential SAP score and banding if all recommendations are implemented

Figure 5.3.2 – The Environmental Impact Rating (EIR) graphic showing the A-G banding with their respective range of EIR scores, the current EIR score and banding of the property, and its potential EIR score and banding if all recommendations are implemented

In terms of the proposals for the private rented sector, it is the energy efficiency rating that is being used as the basis of the standard^[51], and not the environmental impact rating.

The EPC also presents a list of technically feasible ‘Recommended measures’ derived from the assessment of a property, relevant to that property, that would improve both the energy efficiency rating and the environmental impact rating of the assessed dwelling (see Figure 5.3.3).

Figure 5.3.3 - An example of the “Recommended measures” report on an EPC demonstrating their cumulative, sequential impact on the property assessed.

The recommended measures that appear on the EPC are selected automatically by the assessment software; for domestic building assessments, based upon the building data input and assigned based on a method described under Appendix T of the SAP methodology^[52]. While assessors may de-select measures based on site or building related issues not captured in the standard data for RdSAP, they cannot add measures to the list of recommendations.

5.3.2 Identifying the issues

The starting point here was the expressed dissatisfaction seen in many contributions with what is currently included in the EPC recommendations, or how it is presented, and looking forward, what should be included in the recommendations / report. These concerns are reflected in the following quotes:

“Introduce a practical assessment of the properties to be adopted alongside the EPC which will address the practical issues of whether it makes sense to carry out the works and whether they will cause future issues of condensation etc. in the property.”^[53]

“understand that RdSAP/EPC system links information from the survey to a database of costs of measures. However, these do not relate to the reality found during insulation installation projects for traditional buildings and, according to the database, some costs e.g. solid wall insulation cost the same if you are in a 5 room or 6 room house, which we feel cannot be correct.”^[54]

An assessment of the lowest cost approach to bring the property up to standard appears to be a useful starting point, but it will be necessary for the assessors to be sufficiently well trained to understand what is and is not appropriate for properties of different construction types so that their recommendations are practical, relevant and safe, rather than, as all too often, simply formulaic.”^[55]

Contributions relating to the broad themes of ‘Reporting’ (n=299) and ‘Improvements’ (n=289) extended across 19 of the Keyword categories, however, by far the most frequent issues with EPCs and how ‘Improvements’ are described were within the contributions relating to ‘recommendations’ and ‘minimum standards’ (see Table 5.3.1). The pivot table analysis set out in Appendix A.4 indicates that the overwhelming majority of these contributions (85%) came via the public responses to the PRS consultation and focussed on domestic sector; only one of the 289 responses on ‘Improvements’ related exclusively to the non-domestic buildings.

Comments related to ‘minimum standards’ were on the whole directed at suggesting how the EPC could be used as a means to communicate the ways in which dwellings could be improved to meet the minimum standards:

“the assessment should set out the lowest cost package of measures required to bring the property up to standard.”^[56]

“the assessment should set out the package of measures to meet an energy efficiency rating of E, and separately of D, from the property’s current rating.”^[57]

This is not surprising as the format of the PRS consultation specifically invited respondents to offer opinions on how the EPC could be utilised to provide such information to occupants^[58].

Table 5.3.1 - Frequency analysis on response terms under Reporting and Improvements themes

Keyword	Broad themes
	Reporting	Improvements
recommendations	180	180
minimum standards	52	52
performance gap	9	6
quality assurance	8	7
reporting	7	1
surveyor skills	7	7
traditional buildings	7	7
district heating	6	6
new technologies	5	7
decarbonisation	4	4
metric	4	5
benchmarking	2	-
review and update	2	1
alternative model	1	1
electric heating	1	1
flawed	1	1
hard to treat	1	1
room in roof	1	1
thermal imaging	1	1
Total	299	289

Six particular issues with regard to EPC reporting and recommendations were identified through the analysis:

• Appendix T
• the Product Characteristics Database (PCDB)
• meeting minimum standards
• recognising new technologies
• the RdSAP metric
• the format of the recommended measures table on the EPC

The frequency analysis relating to these issues are set out in Table 5.3.2 below.

Table 5.3.2: Frequency analysis of EPC reporting and recommendation issues (by issue classification)

Issue	Assessment	Calculation	Reporting	Total
Appendix T Method	40	11	99	150
Format Recommendations Table	10	22	25	57
Product Characteristics Database	3	7	40	50
Minimum Standards	10	1	39	50
Metric	14	10	25	49
New Technologies	1	4	4	9
total	78	55	232	365

The role of the assessor within the reporting and recommendations process is not well understood. While the recommendations are based on the information collected by the assessor and entered into the respective program; the assessor has a role in providing reliable and correct data in accordance with the conventions. Beyond that, the assessor is somewhat irrelevant to the process: the selection of the recommendations, the determination of the costs of the measures for domestic buildings, and the calculation of the savings on fuel bills or the return on the investment are governed by Appendix T and the PCDB – two components of the software currently outwith the control of the assessor.

The PCDB^[59] which provides the reference values used in the calculations of the location-specific fuel bills on the EPC is regularly reviewed and revised as necessary. Product specific information (e.g. new boilers and boiler efficiencies) are updated monthly; localised fuel prices are reviewed 6-monthly. By contrast, the base costs used to calculate the ‘Indicative costs’ of the ‘Recommended measures’ table do not appear to have been updated since 2012^[60]. It is understandable that contributions questioned the validity of the improvement measure costs published on the EPC or their rates of return, or suggested that this could be an area where users could input their own prices. The need for, and added costs of requisite building warrants and / or planning applications are not factored into the costs presented on the EPC; occupants need to be made aware of such additions when considering the value of investment in energy efficiency.

As the proposed minimum standards are rolled out across the private sector, the cost of meeting these standards is likely to be the focus of more and more attention amongst landlords and owners. The analysis prepared for the Scottish Government on developing the regulation of energy efficiency of private sector housing explicitly examined the lowest cost associated with meeting various energy efficiency standards for 355 archetypes^[61]; the EPC is currently not designed in a way to replicate this type of approach, nor the software designed to calculate the costs in such a manner.

The development of new technology is outpacing the ability of the modelling to capture its impact either in terms of energy efficiency or on the running costs for occupants. RdSAP, in particular, is very poor in the way that new technologies are handled.

The recommendations on the EPC are not customised to the occupant, nor are they produced in way that encourages selective decision making, picking and choosing single improvements on an informed basis. The existing EPC reports an aggregated EPC rating, improving as each measure is modelled in sequence, which is not useful when looking at the impact of specific measures. The appropriateness of recommended improvements needs to be highlighted and occupants directed to seek professional help in assessing the risks:

“the EPC assessment should be used as part of a minimum standards assessment and that the methodology is utilised as part of this”^[62]

“the Standard Assessment Procedure (SAP) methodology cannot substitute for a design approach to building improvements and any methodology which is hard coded into SAP runs the danger of promoting inappropriate interventions which harm the building fabric or historic value of traditional buildings.”^[63]

If EPC reports are to offer more-tailored recommendations to building owners, or possibly use real data in the improvement cost calculations and the estimation of potential savings, there would need to be major changes to both the assessment software and the EPC format.

5.4 SAP, RdSAP and the EPC Metrics

5.4.1 Measuring Energy Efficiency

The ‘energy efficiency’ of a property can be expressed in many ways: the SAP score is one way. Importantly, SAP is an energy cost index: it combines energy consumption, energy efficiency and fuel prices into a single number. In simple terms, it is an expression of the cost to achieve a specific space heating regime, and provide adequate hot water and sufficient lighting, divided by the dwelling’s total floor area (i.e. £/m²). It was designed to be insensitive to floor area so that big houses could be compared with small flats. It is an asset rating: it is about the property, and uses standardised assumptions on the occupants and their use of fuel. It is not about the actual occupants or their use of the property; and these can be decidedly different from the assumptions.

‘Miles per gallon’ is a commonly understood metric associated with the energy efficiency of a motor car; the same cannot be said about SAP. As a measure of energy efficiency, improving the SAP score will occur if the improvements impact on a part of the energy system providing the amenity of space heating, water heating and/or lighting. Other actions that may reduce energy consumption (e.g. using microwave energy over a thermal appliance for cooking purposes or swapping to a A+++ fridge freezer from an older ‘B’ rated appliance) may reduce energy consumption and improve energy efficiency, but are outside the scope of the EPC metric.

Within SAP and RdSAP, all fuels have an associated cost. The calculations utilise nationally derived fuel costs assigned to them regardless of what the building occupant is actually paying^[64]. SAP and RdSAP are not biased against rural areas as such, but if a building is reliant on a fuel other than mains gas^[65] (e.g. being off the gas grid), then it will result in a lower SAP score even if everything else about the building was identical and the fuel was sourced for free by the occupants.

5.4.2 Identifying the Issues

The starting point here is the very evident dichotomy within the public perception of SAP, RdSAP and the EPC metrics as expressed in the following two quotes:

“Landlords, tenants and householders are becoming more familiar with the EPC, and it is already used in the Tenant Information Packs, marketing materials, and required at change of tenancy. The A-G scale provides a simple understanding of the energy performance of the property as it compares with other properties in the UK that is readily accessible. A literature review from ClimateXChange found that members of the public thought the A-G scale was a ‘key strength’ of the EPC as it is ‘easily understandable’.“^[66]

“As a tool for the mass market RdSAP/EPC is not a good product. At the moment it is a product that can only be understood by trained assessors and even then they often cannot explain the output.”^[67]

Contributions relating to the values and metrics contained within the EPC were on the whole split between the broad themes of ‘Methodology’ (n=355) and ‘Modelling’ (n=124) (see Table 5.4.1). It can be seen in the pivot table analysis in Appendix A.4, that the responses within the ‘Methodology’ theme were sourced primarily from the PRS consultation responses (65%) with only 4% coming from the LHEES consultation responses, and 30% from SEEP. With regard to the ‘Modelling’ theme, more were sourced from the LHEES responses (12%) and less from the SEEP responses (19%), but the PRS consultation responses were still the main source of the responses (69%).

Table 5.4.1 - Frequency analysis on response terms for metric focussed issues for Methodology and Modelling broad themes by Keyword

Keyword	Broad themes
	Methodology ‘metric’	Modelling ‘metric’
performance gap	84	18
metric	66	33
awareness of SAP	40	19
recommendations	27	4
decarbonisation	18	3
flawed	16	10
minimum standards	12	1
quality assurance	12	-
review and update	12	2
traditional buildings	11	2
benchmarking	10	3
electric heating	10	1
fuel poverty	6	2
district heating	5	4
real data	4	4
reporting	4	4
affordable warmth	3	1
surveyor skills	3	-
ventilation	3	1
database	2	6
administration	1	-
alternative model	1	4
conventions	1	1
embodied energy	1	-
hard to treat	1	-
room in roof	1	-
thermal imaging	1	1
Grand Total	355	124

This analysis identified 3 particular issues with regard to the SAP and RdSAP metrics:

• metrics and asset ratings
• the use of real data
• occupancy factors

These are set out in Table 5.4.2 below.

Table 5.4.2: Frequency Analysis of SAP and RdSAP-related metric issues by Issue Classification

Issue	Calculation	Assessment	Reporting	Database	Total
Metrics / Asset Ratings	168	57	128	2	355
Real Data	40	16	45	9	110
Occupancy Factors	46	10	50	0	106
Total	254	83	223	11	571

The concept of a rating scale is easy to understand: the closer the letter is to ‘A’, the better, and this has received public support. From the total of 73 contributions of the total of 1066 from the three public consultations that were categorised as ‘positive’ with regard to SAP, RdSAP, SBEM, and EPCs, 62 (i.e. 85%) of them were related to ‘metrics’ within the methodology theme.

The rest of the EPC is perhaps less accessible and understood. The EPC appears to the average lay person as a very technical document. While the public are mostly aware of the EPC in relation to selling or renting a property, if the purpose of the EPC is to engage with the population in order to encourage a greater interest in energy efficiency and the impact that this may have from a fuel cost, energy efficiency, or environmental viewpoint, the data presented needs to be more user friendly for the householder, e.g. values such as ‘Primary Energy Indicator’ are just not easy to understand.

Robust reasons underpin the choice of metric for assessing the energy performance of a building: cost was seen as providing a consistent method to account for the relationship between price and delivered energy efficiency. However, if the policy focus is on emissions, then the use of fuel cost rather than kWh or CO₂ emissions penalises low carbon fuels when compared against lower cost but higher carbon fuels, with possible negative outcomes for climate change e.g. comparing biomass against mains gas or kerosene. If the policy intention is to use EPCs to promote a lower carbon future, then behaviour change is an important factor as this impacts on actual energy use, and therefore emissions in the real world, not modelled energy use; and not just space and water heating and lighting, but all energy use in the building:

“emissions from domestic and non-domestic buildings respectively must rely heavily on decarbonising the supply side … applying to heat only … modest targets are again for regulated heat when a significant proportion of demand is for unregulated electricity to power white goods, electronic devices, etc.”^[68]

The EPC itself actually reflects two different metrics at work. The SAP score is based on standardised fuel costs, heating patterns, and occupancy assumptions for a single climatic zone in the UK^[69]. The energy running costs set out on the EPC are derived from the PCDB (see Appendix A.7) and are updated every 6 months and utilise postcode-based climatic data (i.e. external temperatures, wind speed, and solar radiation on horizontal surfaces). Relocating a dwelling anywhere in Scotland will not change the calculated SAP score; however, the calculated fuel costs, energy demand, emissions, primary energy use, and potential savings, will all change on the EPC.

“We would like to give the energy assessors a ‘tool’ to extend the EPC to include an occupancy evaluation, thus providing the asset rating (EPC), and overlaying this with the occupation details to create ‘tailored’ recommendations for the tenants/landlords and the property.”^[70]

The Green Deal Advice Report set a precedent for using the EPC-derived data to prepare energy advice reports tailored to individual householders, their circumstances, their use of the dwelling, heating and other appliances, and what they were actually paying for fuel: the asset rating remained unchanged, but the underlying data was imported into a separate program. The ensuing recommendations were very different from those on the EPC. Such an individualised assessment does not allow for comparison with other properties on a like-for-like basis.

Using real data over time could improve our understanding of how occupants actually use their properties and also how properties respond to being used in non-standard ways. In addition, half hourly metering data from smart meters could be utilised for the purposes of better understanding how energy is used over a 24 hour period and throughout the year. If real cost data is used for measures, then this could also account for the embodied energy of the measure, to allow for a more comprehensive environmental impact assessment. These issues are currently beyond the existing scope of the SAP, RdSAP and SBEM metrics.

5.5 Non-domestic Buildings

5.5.1 Different requirements from domestic dwellings

Non-domestic buildings were separated out from the examination of either domestic building-related contributions, or those that could pertain to both domestic and non-domestic buildings. Non-domestic buildings have a separate assessment methodology and software, and their EPCs have a different format.

The rating scale of G (very poor) to A+ (excellent) mirrors that seen for domestic dwellings, but the basis of the Building Energy Performance Rating is an assessment of the kg of CO₂ per m² per year emitted from the building, that is, more akin to the Environmental Impact Rating on the domestic building EPC than the SAP-based energy efficiency rating (see Figure 5.5.1).

Figure 5.5.1 – Building Energy Performance Rating graphic showing the A-G banding with their respective range of kg of CO₂ per m² per year values, the BEPR score of the property assessed, and its potential BEPR score and banding if all recommendations are implemented.

The recommendations for non-domestic buildings are banded by their payback period (short, medium and long term) with indicative potential impacts rather than the more quantified savings seen on the domestic EPC (see Figure 5.5.2).

Figure 5.5.2 - An example of the “Recommended measures” report on a non-domestic EPC demonstrating the separation of improvements into short, medium and long term payback, as well as the indicative potential impact for the property assessed.

There is considerably greater diversity in terms of size and purpose, as well as the uses within they are put to, than would be expected from houses. The energy demands and energy profiles within non-domestic buildings may be significantly different from that found in housing: space heating may not be particularly important compared to the needs for lighting, process and motive energy.

5.5.2 Identifying the Issues

When examined by the Keywords, the non-domestic specific contributions extended across only 8 of the 35 keywords. Almost half of the non-domestic contributions (14 of the 31) were concerned with benchmarking with the remaining 17 contributions spread across the other 7 keywords (see Table 5.5.2).

Table 5.5.2: Frequency of Keywords by Consultation (non-domestic only)

Keyword	LHEES	PRS	SEEP	Total
benchmarking	0	2	12	14
real data	4	0	1	5
performance gap	0	1	3	4
recommendations	0	1	2	3
alternative model	2	0	0	2
surveyor skills	1	0	0	1
new technologies	0	0	1	1
review & update	0	0	1	1
Total	7	4	20	31

For the non-domestic specific issues, the greatest concern was with benchmarking, and this concern was spread across all three issue classifications (see Table 5.5.3). In total, eight issues were identified.

Table 5.5.3: Summary of keywords by Issue Classification (non-domestic only)

Keywords	Calculation	Assessment	Reporting	Total
Benchmarking	3	5	6	14
Real data	4	1	0	5
Performance gap	3	0	1	4
Recommendations	0	1	2	3
Alternative models	2	0	0	2
Surveyor skills	0	1	0	1
New Technologies	1	0	1	1
Review and Update	13	8	10	31

Benchmarking requires availability of energy consumption data and can then be used to prioritise measures/actions. Non-domestic buildings are not as homogenous as domestic dwellings; therefore it can be difficult to make comparisons between buildings used in different non-domestic sectors. The barriers to energy efficient retrofits (e.g. insulation) are more significant than for dwellings. A number of the contributions signposted to recent publications and methodologies from other countries. A preference was indicated for operational ratings rather than asset ratings and a suggestion made for funding of longer-terms measures for older buildings. Reference was also made to two UK government initiatives: the Carbon Reduction Commitment^[71] and Energy Savings Opportunities Scheme^[72].

In Scotland, some larger non-domestic buildings^[73] are already required to display an EPC. These are asset ratings produced via SBEM or other approved dynamic simulation models. These requirements are different from than the rest of the UK, where there are obligations to have Display Energy Certificates (DECs) on display in non-domestic buildings with a floor area of 250m² or more. The significant difference is that DECs are based on the operational performance of the building, comparing actual measured energy of the building over the past year with a typical building of the same type.

Collecting operational data would assist in benchmarking a building’s actual energy performance, and Scotland is moving in that direction. Under Section 63 of the Climate Change (Scotland) Act^[74], from September 2016, the owners of non-domestic buildings of more than 1000m² are required to “assess and set out action to improve the emissions and energy performance of their buildings where offered for sale or for rental to a new tenant. The owner must then either improve the building within a specified period or report annually on its actual energy use, until such time as he/she has completed improvements.”^[75] The annual report is to be via a DEC. Both the action plans and / or the DECs are to be lodged on the Scottish register.

It is difficult to compare energy efficiency and heat decarbonisation performance between different commercial buildings, which vary according to age, location, function and access to energy. The EPCs refer to building energy consumption only and not, for example, process energy or electric car-charging points. The EPC recommendations cannot simply be translated into costs and actions and enhanced energy audits are needed.

Recommendations from the EPCs can be used to build a robust business case for energy efficient investments but they are not mandatory. There can be a significant difference between EPC recommendations and guide costs and viable works and costs once on site.

SBEM and the NCM are not the only assessment tools available and are relatively simple models. There are many commercially available, dynamic simulation models that can be used in the design and assessment for new and existing buildings.

Completing energy assessments in the non-domestic sector requires a higher skills base, expertise and experience than the equivalent exercise in the domestic sector.

Technologies are always evolving, and the software is always playing catch up.

The concept of EPCs, where it was explicitly commented on within the non-domestic contributions, was considered a sound basis to build upon, as was the DEC use of real data in other parts of UK – both should be utilised, but expanded to be fit for purpose going forward.

Whilst the NCM and the non-domestic EPC assessment is used as a part of the current process for assessing and improving larger non-domestic buildings, it should be noted that the further action to determine a set of improvement measures that will be applied to the building to meet energy and emissions improvement targets is delivered by a further assessment and advice function (the Section 63 Advisor) and recorded on a separate document (the Action Plan). EPC recommendations are not used for this purpose and targets are not set based upon the EPC rating. This process is set out at www.gov.scot/section63 and is subject to a review process as part of revision of standards for 2021.

5.6 Assessors

5.6.1 Assessors – The public perception

There were a significant number of responses relating to the competency and skills of assessors and in general these were not positive, with concerns raised around quality assurance, integrity and consistency.

5.6.2 Identifying the Issues

The thematic analysis categorised the 286 responses pertaining to assessor-related issues across the three public consultations according to one of three concerns and extending across 7 keywords (see Table 5.6.1). Overwhelmingly, the responses on assessor-related issues came from the PRS consultation: 253 of the 286 (i.e. 88.5%) responses.

Table 5.6.1: Frequency of Broad theme: Assessor by Keywords

Keyword	Broad theme: Assessor
	competence	integrity	quality assurance	total
Surveyor skills	206	0	0	206
Quality assurance procedures	0	0	24	24
Quality assurance: consistency	0	0	20	20
Integrity	0	17	0	17
Independence	0	12	0	12
Accountability	0	0	6	6
Improvements	0	0	1	1
Total	206	29	51	286

Most of the contributions were classified as being concerned with assessment-related matters (see Table 5.6.2).

Table 5.6.2: Identifying the Issues within the Assessor Responses by Issue classification

Keywords	Calculation	Assessment	Reporting	Total
Surveyor skills	0	200	6	206
Quality assurance: procedures	0	24	0	24
Quality assurance: consistency	0	20	0	20
Integrity	0	16	1	17
Independence	0	12	0	12
Accountability	0	5	1	6
Quality assurance: improvements	0	1	0	1
Total	0	278	8	286

The issue of competence / surveyor skills dominates the concerns with regard to assessor-related contributions. The PRS consultation raised specific queries concerning EPC assessors, and the need for more skills and more training.

What emerges from this analysis are three areas of concern:

• surveyor skills / competence
• quality assurance consistency and procedures
• assessor integrity and independence

While we can improve the underlying methodology and procedures to improve accuracy of the models, these improvements do not address public perception of a system where there are fundamental concerns about surveyor competence, conflicts of interest, and gaming of the system. Public confidence and public buy-in to the EPC framework will depend on the public being convinced on the robustness of the procedures and the integrity of the process.

5.7 Technical issues: Room in the roof dwellings

The thematic analysis only described 1 response by the keyword ‘room in the roof’ which fell within the Built Form broad theme. However, within the Built Form broad theme, a further 7 responses were described as being concerned with room in the roof issues (see Table 5.7.1). These responses fell across three other keywords (see Table 5.7.2)

Table 5.7.1: Frequency analysis of descriptors within ‘Built Form’ theme

Broad theme: Built Form	contributions
traditional	73
older	12
rooms in roof	8
non-traditional	4
hard to treat	3
Scottish housing stock	2
size	1
whole building	1
pre-1919	1
pre-1940	1
masonry	1
Total	107

5.7.1 Identifying the Issues: Rooms in the Roof

All 8 of the room in the roof contributions were also described under both the Methodology and Modelling broad themes (see Table 5.7.2). The issues of use of defaults, the PCDB, accuracy, and U-values were identified as the concerns.

Table 5.7.2: Frequency of room in the roof contributions broken down by Methodology and Modelling broad themes and keywords

Keyword	Broad theme: Methodology (n=8)		Broad theme: Modelling (n=8)
	Defaults	PCDB	Defaults	Accuracy	U-values
Recommendations (n=4)	1	3	3		1
Performance gap (n=2)	2			1	1
Conventions (n=1)	1		1
Room in roof (n=1)	1			1
Total	5	3	4	2	2

When ‘rooms in the roof’ were filtered, all of 8 the responses returned ‘defaults’ under either the Methodology and / or Modelling categories. The use of defaults in the assessment of rooms in the roof is seen as an issue.

Going beyond the use of defaults, three other specific issues emerge:

• the use of the PCDB in the costing of room in the roof improvements recommended by the EPC;
• the accuracy of the results; and,
• the resultant U-values assigned by the RdSAP defaults.

When the 8 room in the roof contributions were filtered by the Conventions broad theme, three of them identified consistency between assessors as a concern.

As part of this review, a separate Supplementary Topic Note (see Section 5.12) was prepared on issues concerning rooms in the roof, including the confusion within the conventions over when to measure rooms in the roof, the need for better direction with regard to assessor discretion, and the need for improving the definitions of rooms of the roof. This Supplementary Topic Note is published as an addendum to the main report.

5.8 Technical issues: District and Community Heating, Combined Heat & Power

5.8.1 Local Heat Networks in Scotland

Local heat networks are being proposed as an important element in shaping Scotland’s energy future. This review was concerned with the LHEES responses to the consultation that opened in January 2017. Since then a second consultation was carried out between November 2017 and February 2018 on more specific policy proposals for Local Heat & Energy Efficiency Strategies and regulation of district and communal heating^[76].

5.8.2 Identifying the Issues

Within the ‘heating theme’, the thematic analysis categorised 19 contributions as pertaining to district heating / community heating / combined heat and power (DH/CHP) across the responses to the three consultation documents, as well as by the keyword ‘district heating’. The other two prominent concerns within the ‘heating’ theme (i.e. electric and low carbon) were mostly concern with how poorly electric heating scores in SAP / RdSAP, and concern with the undervaluing of low carbon renewables: these issues are dealt with more fully under the SAP and RdSAP metrics – see section 5.4)

Table 5.8.1: Frequency analysis of descriptors within ‘Heating’ theme

Broad theme: Heating	contributions
Electric	20
District heating	19
Low carbon	15
Heat pumps	3
Thermal storage	3
Wood	3
Sizing	2
Infra-red heating	1
Micro co-generation	1
Portable	1
Total	64

All of the DH/CHP contributions were also described under both the Methodology and Modelling themes (see Table 5.8.2), and these are broken down by their Issue Classification in Table 5.8.3.

The two most common issues with regard to DH/CHP were:

• the accuracy of the results; and,
• the use of defaults in the calculations

Other issues such as the use of real data, Appendix T and the PCDB were of a lesser concern.

Table 5.8.2: Frequency of district heating contributions broken down by Methodology and Modelling themes

Descriptors	Methodology	Modelling
Accuracy	-	10
Defaults	4	5
Real data	1	4
Appendix T	4	-
Metric	3	0
Mapping	3	0
Alternative Models	2	-
PCDB	2	-
Total	19	19

Table 5.8.3: Identifying the Issues within the DH/CHP contributions by Issue Classification

Broad themes: Methodology and Modelling	Calculation	Assessment	Reporting	Database	Total
Accuracy	10	0	0	0	10
Use of Defaults	5	0	4	0	9
Appendix T	0	0	4	0	4
Real Data	1	1	0	3	5
Mapping	0	0	0	3	3
Metric	2	1	0	0	3
Alternative Models	2	0	0	0	2
PCDB	2	0	0	0	2
Total	22	2	8	6	38

The potential benefits of DH/CHP will not be realised if they are not well modelled in SAP, RdSAP and SBEM. The public consultation responses on DH/CHP reflect a concern that these potential benefits may not be realised as they are not fully recognised in RdSAP.

As part of this review, a separate Supplementary Topic Note (see Section 5.12) was prepared on issues relating to DH/CHP, including comparing the impact of the different input parameters used in a full SAP assessment as opposed to an RdSAP assessment of a DH/CHP scheme. This Supplementary Topic Note is published as an addendum to the main report.

5.9 Technical issues: Ventilation

5.9.1 Modelling Ventilation

The rate of ventilation is a key component of the heat loss calculation for all buildings: the more times the air turns over within a building, the more heat needs to be replaced. It is possible to measure the air infiltration rate accurately through using air pressure testing equipment; an alternative is to estimate the air infiltration rate from a number of variables. Within RdSAP, many of the ventilation-related variables are defaults within the program.

5.9.2 Identifying the Issues

The 11 contributions identified under the broad theme of ventilation fell within one of three descriptors (i.e. infiltration, Ventrolla, and draught lobbies), and extended across two keywords (i.e. ventilation and surveyor skills) (see Table 5.9.1)

Table 5.9.1: Frequency analysis of Broad theme descriptors by Keywords within ‘Ventilation’ Broad theme

Keyword	Broad theme: Ventilation			Total
	Infiltration	Ventrolla	Draught lobbies
Ventilation	6	2	1	9
Surveyor skills	2	0	0	2
total	8	2	1	11

All of the ventilation contributions were also described under both the Methodology and Modelling themes (see Table 5.9.2). The use of defaults was identified as the main concern.

Table 5.9.2: Frequency of ventilation contributions broken down by Methodology and Modelling Broad themes

Descriptors	Methodology	Modelling
Defaults	2	8
Metric	4	1
Appendix T	2	-
Occupant behaviour	1	1
Real data	1	1
Alternative Models	1	-
Total	11	11

The ventilation-related contributions were concerned primarily with assessment-related issues (see Table 5.9.3).

Table 5.9.3: Identifying the Issues within the ‘Ventilation’ contributions

Ventilation descriptors	Calculation	Assessment	Reporting	Database	Total
Infiltration	3	5	0	0	8
Ventrolla	0	2	0	0	2
Draught lobbies	0	1	0	0	1
Total	3	8	0	0	11

As part of this review, a separate Supplementary Topic Note (see Section 5.12) was prepared on issues relating to ventilation, and in particular the default ventilation parameters used in RdSAP compared to full SAP. A sensitivity analysis of the impact of switching some of the defaults to using survey-based data was carried out as part of this modelling. This Supplementary Topic Note is published as an addendum to the main report.

5.10 Technical issues: Measuring windows

Contributions concerned with the measuring of windows or glazing generally did not feature significantly in the contributions to the three public consultations. However, given the nature of this review, this was an area that the authors thought merited more discussion in going forward with regard to whether windows dimensions should be measured or defaulted to within the RdSAP calculation process.

5.10.1 Identifying the Issues

With regard to windows and other glazing-related issues, only 5 contributions falling across four keywords were identified through the thematic analysis (see Table 5.10.1 and Table 5.10.2) Within the ‘fabric’ theme, the two dominant issues (i.e. stone walls and solid walls, plus thermal mass) are dealt with under the overarching topic on traditional buildings (see Section 5.2)

Table 5.10.1: Frequency analysis of descriptors within ‘Fabric’ theme

Broad theme: Fabric	contributions
Stone walls	23
Solid walls	20
Windows	3
Insulation	2
Wall insulation	2
Thermal mass	2
Loft insulation	1
Shutters	1
Glazing	1
Brick	1
Total	56

Table 5.10.2: Frequency analysis of windows-related descriptors by Keywords

Keyword	Broad theme: Fabric			total
	Windows	Shutters	Glazing
Windows	1	1	0	2
Surveyor skills	0	0	1	1
Performance gap	1	0	0	1
recommendations	1	0	0	1
total	3	1	1	5

All of the windows contributions were also described under both the Methodology and Modelling themes (see Table 5.10.3). The use of defaults emerged as the main concern.

Table 5.10.3: Frequency of windows-related contributions broken down by Methodology and Modelling Broad themes

Descriptors	Methodology	Modelling
Defaults	3	4
Appendix T	2	-
Accuracy	0	1
Total	5	5

The windows-related contributions were split between assessment and reporting-related concerns (see Table 5.10.4).

Table 5.10.4: Windows-related contributions by Issue Classification

Window-related descriptors	Calculation	Assessment	Reporting	Database	Total
Windows	0	2	1	0	3
Shutters	0	1	0	0	1
Glazing	0	0	1	0	1
Total	0	3	2	0	5

As part of this project, a separate Supplementary Topic Note (see Section 5.12) was prepared on issues relating to measuring windows, including a comparison of measured window areas of almost 1400 properties from across Scotland with the default areas calculated by RdSAP algorithms – there are significant differences. Additionally, a sensitivity analysis was performed on the impact of using measured window areas, as opposed to the RdSAP model areas, on various energy performance indicators produced by RdSAP. This Supplementary Topic Note is published as an addendum to the main report.

5.11 Workshop design

Four workshops were organised around the nine topics identified in Sections 5.2 to 5.10, that is, the overarching issues and the technical issues. They were arranged as a one-day format and repeated in four locations across Scotland:

• Edinburgh, February 16^th, 2018
• Aberdeen, February 22^nd, 2018
• Glasgow, February 26^th, 2018
• Stirling, March 16^th, 2018

The first three workshops in Edinburgh, Aberdeen and Glasgow followed the same format (see Appendix B). The last workshop, which was held in Stirling, was run in partnership with Historic Environment Scotland (HES) and took a more particular focus on a common theme relating to how the RdSAP/EPC treats historic/traditional buildings.

All four workshops were open events. Invitations were sent out to everyone that could be identified from their response to one of the three publications. In some cases the responses included contact details; where no contact details were provided, their organisations (if identifiable) were contacted. It was not possible to contact everyone that responded to one of the three consultations, either because no contact details were on the response, or in some cases, the contact details had been redacted. Additionally, EAS used a database of known EPC assessors operating in Scotland, as well as circulating details to all of the Approved Organisations operating in Scotland. EAS also published the events throughout their membership.

The intention was to be pro-active in canvassing a diverse array of opinions to encourage discussion on these topics, and to allow feedback to be captured from each participant. Presentations on the broad themes distilled from the thematic analysis, and the sensitivity analysis were used to introduce ‘evidence’ of issues, to seek verification of the validity of the concerns, and to consolidate the research team’s thinking on possible actions on EPCs going forward. The presentations by the research team were followed by facilitated discussions with the participants.

Participants were asked to record any comments and/or their views of this evidence within structured workbooks to allow the research team to determine if this evidence had any bearing on consolidating or changing opinions on the effectiveness of the EPC system in Scotland. It was considered that utilising a mechanism to accurately record views from all participants individually was a more effective method of inclusive data gathering than the commonly employed focus group consensus which can obscure individuals’ comments and suppress polarised views.

A blank copy of the workbook that was used at each event is included as an addendum to this report.

The workshop presentations have been collated, converted to PDF documents, and made available to all participants at the workshops. These collated presentations are also an addendum to this report.

5.11.1 The purpose of workshop outputs

Participant feedback in the workbooks provided at the workshops represented a supplementary data source to the contributions gathered from the three public consultation documents. The intention was to allow robust validation or rebuttal of the evidence provided within each of the topic areas identified allowing the research team to confidently conclude the value of any proposal and suggest ways in which EPC provision in Scotland could be more sympathetic to the Scottish built environment: in effect, a peer review by industry stakeholders.

5.12 Supplementary Topic Notes: SAP/RdSAP sensitivity assessments

The research team carried out additional SAP and RdSAP modelling on a range of specific (domestic) to assess the impact of changing assumptions being made within RdSAP. The research team has access to a resource of the full SAP 2012 assessments for 355 archetypes that were used in the REEPS analysis that was published by the Scottish Government in 2015^[77]. A selection of these properties was inputted into RdSAP assessment software following the rules and conventions employed by EPC assessors. This allowed comparative analysis of EPC results on the same property between full SAP (no inference) and RdSAP where default or ‘best guess’ values are employed to generate the output.

At the core of SAP and RdSAP is the same calculation engine i.e. BREDEM. Where they differ is that RdSAP defaults specific dwelling variables that are taken account of explicitly in SAP (e.g. within the ventilation algorithm the number of extract fans, flues, air vents, trickle ventilation and the presence of a draught lobby are all either defaulted or ignored in RdSAP but counted individually within SAP). Outputs from this sensitivity testing activity focused on the differences in terms of the SAP rating, the energy demand, CO₂ emissions, and the modelled fuel costs from the two assessment procedures.

Sensitivity assessments were carried out using various real data sets on:

• comparing the differences between measured window areas with RdSAP calculated areas on 1398 Scottish dwellings;
• comparing the impact of measured window areas with RdSAP calculated areas on savings calculated for wall insulation for 26 pre-1919 sandstone tenemental flats in Glasgow;
• comparing the impact of adjusting RdSAP default ventilation factors to match actual data from dwelling surveys on 183 REEPS archetypes;
• comparing the impact of using a full SAP assessment of community heating with an RdSAP assessment on 55 flats in a multi-storey high rise in Aberdeen;
• comparing the impact of altering the assumptions about the RdSAP thermal mass default on 100 REEPS archetypes;

Additionally, a modelling exercise was completed to assess the effect of changing a variable within the RdSAP stone wall U-value equations, as proposed by a representative from Historic Environment Scotland at one of the project’s workshops, on a range of stone wall types and thicknesses.

The results from these sensitivity and modelling exercises are presented in more detail in the Supplementary Topic Notes document that is an addendum to this report. The results were used to inform the results and recommendations of this report.