Domestic and non-domestic energy performance certificates: review

Analysis of responses to our three public consultations about energy performance certificates (EPCs).





4. see p7, Energy Efficient Scotland: A Route Map,

5. for example, the Energy Efficiency Standard for Social Housing (ESSH), see /policies/home-energy-and-fuel-poverty/energy-efficiency-in-social-housing/

6. for example, Energy Companies Obligation (ECO): Guidance for Suppliers published by Ofgem in 2013, available at

7. “If your Energy Performance Certificate (EPC) is dated after September 2012 it has all of the information on it that we need to calculate the payments you could get from the Domestic Renewable Heat Incentive.” see





12. there is a paper copy of the SAP worksheet included within the SAP manual, so that the calculation could be completed by hand using the look up tables included within the SAP manual

13. “HUE was applied on behalf of the Scottish Building Standards Agency to meet the requirements of the EU Energy Performance of Buildings Directive, which calls for the issuing of performance certificates. When used by SBSA, HUE is known as the Scottish Energy Rating Tool, or SERT. Within the project, the HUE predictions were shown to be well aligned with the Government’s simplified domestic sector method known as SAP” taken from

14. see

15. see (We are in the process of migrating SAP webpages from our old website to this new platform. Once the migration is complete all SAP related information, links and downloads will be made available via this site.)

16. ibid

17. see

18. For the NCM technical manual see

19. For current SAP 2012 v9.92 manual see

20. For current RdSAP v9.93, see

21. See Department of Business, Energy & Industrial Strategy (2017) “Changes to Government’s Standard Assessment Procedure (SAP): Government Response”, available at



24. For SAP 2012, see

25. For RdSAP 2012 v9.93, see

26. For NCM in Scotland, see


28. It is has been reported to the authors of this report that at least one utility has an agreement with the Scottish Register to search through back EPCs as part of its quality assurance activities with regard to ECO2 and ECO2T.

29. Only responses from respondents who gave permission to be published on-line were assessed. The authors of this report had no access to responses where the author(s) of a response withheld permission for it to be published on-line.










39. The individual published responses were identified on the website by either a unique response number or by the name of the organisation or individual making the response. When these latter responses were opened, a unique response number for each was found within. This number was assigned to these responses so that the spreadsheet was anonymous collation of the responses.


41. See

42. SAP 2016 was renamed formally as SAP 10 with the publication of the government response on SAP.

43. See

44. A contribution could be assigned to more than one theme

45. During the initial categorisation of public responses to the consultation documents all mentions of the words ‘historic’ or ‘listed’ with regards to buildings’ built form were classified as ‘traditional’ within this category

46. Taken from response 36838773 available at

47. Taken from response 471251986, available at

48. Not classified in this broad theme

49. Not classified in this broad theme

50. Non-domestic sector buildings are considered elsewhere in this report.

51. The energy efficiency rating is already used as the basis of the EESSH obligation with social housing landlords.

52. Set out in pp162-171 of the SAP 2012 methodology, available at

53. Response 8314891 taken from

54. Response 513682743 taken from

55. Response 19115688 taken from

56. Response 447620038 taken from

57. Response 742030389 taken from

58. There were 55 comments on the subject of minimum standards of which 53 came from the PRS consultation. The two other comments were found in the SEEP consultation and both back-referenced the ‘minimum standards assessment’ question raised in the PRS consultation.


60. See

61. ibid

62. Response 433809798 taken from

63. Response 816313150 taken from

64. For SAP and RdSAP these prices are set out in Table 11 of the SAP 2012 manual, available at

65. Mains gas is the cheapest fuel within SAP / RdSAP, though there some areas with LPG and LNG networks governed by Special Condition 18, whereby the price of LPG or LNG on the local network is tied to the average mains gas price.

66. Response 377886956 taken from

67. Response 385144840 taken from

68. Response 114630764

69. The East Pennine region is used as it is considered to be the UK mean average climatic zone. All Scottish climatic zones are colder and windier.

70. Response 847124774 taken from

71. The initial Carbon Reduction Commitment has since evolved into the CRC Energy Efficiency scheme which, after the March 2016 Budget, will close after the 2018/19 compliance year. See

72. The Energy Savings Opportunities Scheme (ESOS) is a mandatory assessment scheme for UK organisations that meet the qualifying criteria managed by the UK Environment Agency. It is intended to increase awareness of the energy consumption to make it easier for businesses to take action.

73. Since 9 July 2015, buildings occupied by public authorities with a floor area of 250m2 or more frequently visited by the public must have an EPC on display. For other non-domestic buildings frequently visited by the public, the size threshold is a floor area of 500m2 or more, and the obligation to display the EPC is contingent on the building having one. see Guidance Leaflet: Requirement to display Energy Performance Certificates (EPC) available at:


75. Building Standards Division (2016) Improving Energy Performance and Emissions in existing Non-Domestic Buildings - A guide for Building Owners, s63-001, version 1.1 July 2016, para 18, Building Standards Division, The Scottish Government, Linlithgow. available at:

76. see


78. Convention 8.01, RdSAP Conventions 10 from December 31, 2017, available at

79. and any other age category up to 1965

80. see existing guidance notes at

81. for example, see the description of the research methodology within BRE (2014) In-situ measurements of wall U-values in English housing, BRE, Garston, available at

82. Most recently, in RdSAP in November 2017, with the introduction of version 9.93 of the software

83. SEEP Pilot Evaluation – information for applicants, available at

84. Renfrewshire Council Invitation to Tender: Property Monitoring and Design Support for HEEPS ABS Programme, published 31st May 2018, available at

85. for example, a pre-1919, 600mm thick sandstone lath and plaster wall will have a different U-value than a 600mm thick sandstone wall plastered on the hard, and both will have different U-values to the corresponding granite walls

86. BS EN ISO 9869-1: 2014: Thermal insulation -- Building elements -- In-situ measurement of thermal resistance and thermal transmittance -- Part 1: Heat flow meter method

87. Sedimentary type stone are to be classified in RdSAP as sandstone / limestone, while igneous and metamorphic stone are to be classified as granite / whinstone

88. These variations are examined in more depth in Supplementary Topic Note 1 (published as Addendum to this report)

89. Appendix S, RdSAP 2012, v9.93 available at

90. BRE (2014) In-situ measurements of wall U-values in English housing, BRE, Garston, available at

91. Table 1 of the BRE 2014 report (ibid) shows the median measured U-value for standard solid brick walls (i.e. less that 330mm thick) to be 1.59 W/m2K compared with the median calculated U-value of 1.92 W/m2K – that is a difference 0.33 W/m2K. For non-standard solid walls (i.e. 330mm or more thick or comprised of another material other than brick) the median measured U-value was 1.28 W/m2K compared with the median calculated U-value of 1.68 W/m2K – that is a difference of 0.40 W/m2K.

92. the SAP / RdSAP options are 50, 100, 150 or 200mm of internal or external insulation

93. The SAP / RdSAP defaults are 0.55 W/m2K for 50mm of internal or external wall insulation; 0.32 for 100mm; 0.23 for 150mm; and 0.18 for 200mm regardless of the type of stone, the thickness of the stone wall, and the presence of the air gap in the wall.

94. Many walls are currently being insulated with between 70 and 90mm of insulation, but under RdSAP conventions, an assessor would take this back to 50mm.

95. SAP 2012 Conventions v7.1, pp 37-38, available at

96. ISO 10077-1:2017: Thermal performance of windows, doors and shutters -- Calculation of thermal transmittance -- Part 1: General

97. Historic Scotland (2013) Fabric Improvements for Energy Efficiency in Traditional Buildings, Historic Environment Scotland, Edinburgh

98. See

99. Scottish Office Building Directorate (1987) The Guide to Non-traditional Housing in Scotland 1923 -1955, HMSO, Edinburgh

100. Personal communication with the Scottish House Condition Survey (SHCS) team within the Scottish Government where the data collected over 2014-2016 was analysed using a query provided by the authors of this report. ‘Non-traditional’ is not an existing category in the SHCS data analysis.

101. Taken from response 304464253 available at

102. RdSAP Convention 8.01 notes:

“Recommendations should be removed only if there is documentary evidence showing that a specific recommendation is not appropriate. A listed building or a property in a conservation area is not sufficient grounds in its own right to suppress a recommendation.

If a recommendation is removed this must be recorded in site notes.

Further guidance on specific recommendations can be sought from an appropriate professional organisation, for example heating engineers, building control officers, product manufacturers, trade associations, etc.” See RdSAP Conventions V10, available at

103. See




107. Table 12: Fuel prices, emission factors and primary energy factors []

108. “An energy cost deflator term is applied before the rating is calculated. It will vary with the weighted average price of heating fuels in future so that the SAP rating is not affected by the general rate of fuel price inflation. However, individual SAP ratings are affected by relative changes in the price of particular heating fuels.”, see, p226 (footnote r)

109. Without this correction, the effect of rising fuel prices would result in SAP scores falling over time.

110. Tables 1 and 2: []

111. The SAP and RdSAP options are ‘single’, ‘dual’, ‘18-hour’, ’24-hour’ or unknown electricity meter.

112. See Table 12a of the SAP manual.

113. Scottish Hydro’s 24-hour tariff

114. ScottishPower’s 24-hour tariff

115. In “Energy efficiency and condition standards in private rented housing – A Scotland’s Energy Efficiency Programme Consultation” published by the Scottish Government in April 2017, Question 1.12 in the consultation stated: “We propose to develop a new role of minimum standards assessor … (b) … what additional skills beyond those of an EPC assessor would be needed? (p34). Question 1.16 asked “Do you think it would be helpful for assessors and installers to have a traditional buildings qualification that raises awareness and understanding of energy efficiency measures for older, traditional or vulnerable buildings built prior to 1919?” (p38)

116. Energy efficiency and condition standards in private rented housing: Analysis of responses to the public consultation exercise (published November 2017) available at

117. Historic Environment Scotland already offer such courses, for example, see

118. see for a description of the pilot.

119. for the smart audit rules, see

120. From a high of about 2,500 assessors in Ireland in 2009/10, there are now in June 2018 only 493 registered BER assessors (see )

121. see Rosenow, J., & Eyre, N. (2016). A post-mortem of the Green Deal: Austerity, energy efficiency and failure in British energy policy. Energy Research and Social Science, 21, 141–144.

122. Stuart Fairlie, Elmhurst Energy, email correspondence after Edinburgh workshop

123. Extended room in the roof data was enabled in RdSAP 2009 v9.91 and all versions since.

124. Convention 2.06 in “Conventions (v 10.0) for RdSAP 9.92 and RdSAP 9.93” available at

125. Taken from “Conventions (v 10.0) for RdSAP 9.92 and RdSAP 9.93” available at

126. The NHER Surveyor 3 model utilised four default room in the roof shapes in calculating the components of the room in the roof. While the RdSAP conventions display different room in the roof shapes, the algorithm ignores the shape when calculating the dimensional data of the components.

127. All input data was matched in the two programs with the exception of the data on the combined heat and power system.

128. SAP calculated fuel bills only cover space and water heating, lighting, and some standing charges. They do include costs for other fuel use in the home, e.g. cooking and appliance use.

129. Scottish Building Regulations Technical Handbook 2017 Domestic – Energy, section 6.2.4, p18 available at

130. BS EN ISO 9972:2015 - Thermal performance of buildings: Determination of air permeability of buildings: Fan pressurization method replaces BS EN 13829:2001 specifically cited in the Technical Handbook 2017 Domestic – Energy, Section 6.2.5, p.19

131. Supplementary Topic Note 5 on Ventilation sets out Table S5 in full.

132. Ibid. 3

133. Mechanical ventilations systems are reduced from 6 different system types in full SAP down to one of 2 types in RdSAP, with no additional system descriptors needed, and no PCDF options.

134. See Scottish Building Regulations Technical Handbook 2017 Domestic – Energy, Sections 6.2.4 and 6.2.5 available at

135. Renfrewshire Council Invitation to Tender: Property Monitoring and Design Support for HEEPS ABS Programme, published 31st May 2018, available at

136. As far as the authors of this report are aware.

137. These impressions come from canvassing assessors on whether they measure windows or not at various RdSAP masterclass events organised by Alembic Research and Energy Action Scotland over the years.


139. Pre-2003 uPVC-framed double glazing: 6mm gap = 3.1 W/m2K; 12mm gap = 2.8 W/m2K; 16mm or more gap = 2.6 W/m2K. By contrast all pre-2003 wood-framed double glazing is defaulted to a U-value of 3.1 W/m2K regardless of the gap (which is the equivalent of a 6mm gap, which in many instances is patently underestimating the thickness of the gap).

140. RdSAP Conventions v10.0 for RdSAP 9.92 and 9.93 (applicable from December 31, 2017)

141. See convention 8.01, RdSAP Conventions v10.0 for RdSAP 9.92 and 9.93 (applicable from December 31, 2017)



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