Scottish house condition survey: 2018 key findings

3 Energy Efficiency

52. The energy efficiency of a dwelling depends on its physical characteristics. Factors such as the age of construction, the dwelling type, the heating and hot water systems in use and the extent to which the building fabric is insulated, all affect energy efficiency.

53. Based on information about the characteristics of the dwelling collected in the SHCS physical survey, and using standard assumptions about the make-up and the behaviour of the occupying household, the energy consumption associated with the dwelling is modelled. This allows us to make comparisons of energy use, emissions and energy efficiency ratings between dwellings that are independent of occupant behaviour. Further details on the methodology underpinning these measures of energy efficiency are provided in the Methodology Notes^[14].

54. In this chapter we report on analysis of:

• levels of insulation in Scottish dwellings (section 3.1);
• boiler efficiencies (section 3.2);
• Energy Efficiency Ratings (EER), also known as SAP ratings (section 3.3);
• National Home Energy ratings (NHERs) (section 3.4);
• modelled CO2 emissions from dwellings (section 3.5); and
• Environmental Impact Ratings (section 3.6).

3.1 Insulation Measures

55. Installing or upgrading insulation is one of the most effective ways to improve the energy efficiency of a building. The Energy Saving Trust estimates that an un-insulated dwelling loses a third of all its heat through the walls and a further quarter through the roof^[15]. As a result, insulation can significantly reduce energy consumption and therefore lower heating bills, making it cheaper to enjoy satisfactory levels of thermal comfort^[16].

56. Additional insulation is most commonly added to a property through the insulation of loft spaces and by adding insulating material to external walls.

Key Points

• The majority of loft spaces are insulated. In 2018, loft insulation with a thickness of 100 mm or more had been installed in 94% of dwellings. This is unchanged from 2017 but an increase of 12 percentage points on 2010 levels.
• In 2018, 30% of lofts were insulated to a high standard of insulation (300 mm or more). This proportion has remained about this level since 2015, following year on year increases from the 2010 figure of 5%.
• The proportion of insulated cavity walls recorded by the SHCS was 73% in 2018, similar to the previous year. In the longer term, the share of insulated cavity walls has been increasing, with a 7 percentage point improvement since 2012.
• The proportion of solid wall dwellings with insulation was 19% in 2018, which was similar to 2017, and an increase of 8 percentage points on the 2012 figure.
• Levels of insulation (both loft and wall) are higher in the social sector than in the private sector. 55% of homes in the private sector have wall insulation compared to 70% in the social sector. In the private sector, 59% of lofts are insulated to 200 mm or more compared to 71% in the social sector. These figures are similar to 2017.

3.1.1 Loft Insulation

57. Since 2010, an overall improvement in the uptake of loft insulation has occurred. The proportion of all housing with 100 mm or more of loft insulation has increased by 12 percentage points on 2010 levels with 94% of applicable dwellings insulated in 2018 (see Table 10), similar to the level in 2017. Most of this improvement occurred before 2013.

58. Figure 9 shows the level of loft insulation in all dwellings back to 2003/4. The share of dwellings with no loft insulation has fallen from 6% in 2003/4 to 1% in 2018. Most of this decline occurred before 2010. Since then improvement has slowed down, suggesting that there may be barriers preventing the installation of insulation in the relatively few remaining uninsulated lofts.

59. Over the same period the thickness of loft insulation has increased significantly. In 2018, 62% of dwellings with lofts had insulation with a depth of 200 mm or more (Figure 9). Much of this increase has occurred between 2009 and 2013, when the percentage increased from 27% to 62%. This can largely be attributed to the installation of top-up insulation. The increase in the estimated number of dwellings with loft insulation between 100-199 mm between 2017 and 2018, and the associated decrease with 200+ mm over the same time period, are both within the margin of error of the survey.

60. The percentage of lofts with a high standard of insulation (300 mm or more) has remained similar since 2015, at 30%, following significant increases from 5% in 2010 (the first year the SHCS captured this information). In 2018, 29% of private sector dwellings had a high standard of loft insulation, compared to 33% of dwellings in the social sector; both of these figures are similar to 2017.

Figure 9: Depth of Loft Insulation (where applicable) 2003/04 – 2018

Note: A dwelling is classified as ‘not applicable’ for loft insulation if it has a flat roof or another dwelling above it (i.e. it is a mid- or ground-floor flat).

61. Between April 2008 and December 2012, the UK government Carbon Emissions Reduction Target (CERT) scheme delivered 410,937 loft insulation measures in Scotland^[17] (Table 9).

62. Between January 2013 and December 2018 a further 68,681 loft insulation measures were delivered in Scotland by its successor scheme, the Energy Company Obligation (ECO)^[18].

63. In total, around 480,000 loft insulation measures have been installed under these government programs since 2008.

Table 9: Depth of Loft Insulation (000s), 2010 and 2012 to 2018

Loft Insulation	2018	2017		2016	2015	2014		2013			2012	2010
none	11	9		9	19	15		27			31	42
1mm-99mm	95	101		109	125	143		113			185	279
100mm-199mm	594	563		525	518	528		534			617	822
Subtotal: <200mm	701	673		643	663	686		675			834	1,143
200mm or more	1,135	1,152		1,197	1,161	1,123		1,118			975	621
Not applicable	641	638		612	610	611		606			577	592
All Dwellings	2,477	2,464		2,452	2,434	2,420		2,399			2,386	2,357
Sample Size	2,964	3,002		2,850	2,754	2,682		2,723			2,787	3,114
Cumulative recorded loft insulations under government schemes
CERT (000s)										411		157
ECO (000s)	69	59	53		39		30		10

64. As shown in Table 10 thickness of loft insulation is greater in social sector dwellings than private sector dwellings. In 2018, 94% of private housing lofts were insulated to 100 mm or more and 59% to at least 200 mm. In the social sector, 96% of dwellings had lofts insulated to 100 mm or more, and 71% had at least 200 mm of loft insulation.

65. One of the reasons for this difference between private and social sector is that the Scottish Housing Quality Standard (SHQS), which was introduced in 2004, requires at least 100 mm of loft insulation (see section 6.2.2 for more information).

66. The difference in the proportion of lofts with at least 100 mm insulation between the private and the social sector has been reducing gradually, from 17 percentage points in 2003/04 (81% in the social and 64% in the private sector) to 3 percentage points in 2018 (96% in the social sector and 94% in the private sector).

Table 10: Depth of Loft Insulation (000s and %) by Tenure, 2017 and 2018^[19]

		Private Sector		Social Sector		All Tenures
Year	Loft Insulation	000s	%	000s	%	000s	%
2018	none	10	1%	1	0%	11	1%
	1mm - 99mm	82	6%	13	3%	95	5%
	100mm+	1,350	94%	380	96%	1,730	94%
	100mm - 199mm	494	34%	101	26%	594	32%
	200mm - 299mm	444	31%	149	38%	594	32%
	300mm or more	412	29%	130	33%	542	30%
	Total	1,442	100%	394	100%	1,836	100%
2017	none	9	1%	-	0%	9	1%
	1mm - 99mm	92	6%	9	3%	101	6%
	100mm+	1,354	93%	361	97%	1,715	94%
	100mm - 199mm	480	33%	83	22%	563	31%
	200mm - 299mm	459	32%	142	38%	601	33%
	300mm or more	415	28%	136	37%	551	30%
	Total	1,455	100%	370	100%	1,825	100%
Samples	2018		1,874		472		2,346
	2017		1,895		464		2,359

3.1.2 Wall Insulation

67. The presence of cavity wall insulation (CWI) is becoming increasingly difficult for SHCS surveyors to identify as over time the injection holes age, fade or are covered up by later work. Contractors are also getting better at concealing their work. This may mean that the SHCS under-estimates the number of homes which have had CWI installed (see also section 6.2.2). Despite efforts to maintain the high quality of the SHCS physical survey fieldwork, some misclassifications may remain.

68. In Scotland around three quarters of dwellings have external cavity walls and the remaining one quarter have solid or other construction types of external wall. These “other” types include steel or timber-frame dwellings and dwellings made from pre-fabricated concrete. As the improvement of solid and other wall types generally requires more expensive interventions than CWI, this diverse group is addressed together in this chapter.

69. Table 11 and Table 12 show the number and proportion of insulated dwellings by type of external wall. Higher insulation levels in new buildings have been required by building standards since 1982. These dwellings are therefore treated as insulated when built.

Table 11: Cavity Wall Insulation, 2012 and 2014 to 2018^[20]

	2018		2017		2016		2015		2014		2012
	000s	%	000s	%	000s	%	000s	%	000s	%	000s	%
Not insulated	500	27%	457	25%	512	28%	525	29%	518	29%	606	34%
Insulated	1,331	73%	1,363	75%	1,323	72%	1,286	71%	1,287	71%	1,157	66%
Total	1,831	100%	1,821	100%	1,834	100%	1,811	100%	1,805	100%	1,772	100%
Sample		2,240		2,284		2,154		2,099		2,017		2,051
Cumulative reduction in SHCS uninsulated CWI since 2007
000s	316		359		304		291		298		210
Cumulative recorded CWI installations under government schemes since 2007, thousands
CERT											218
ECO	100		91		82		72		54

70. In 2018, 73% of cavity wall dwellings in Scotland were insulated (Table 11), similar to 2017. We know from administrative data that 9,543 cavity wall dwellings were insulated with CWI during 2018 (through ECO). Although the percentage of insulated cavity wall dwellings identified through the SHCS appears to have decreased, this is not a statistically significant difference and reflects that this is a sample of all dwellings.

71. The longer term trend, showing a decrease in the share of uninsulated cavity walls of 7 percentage points since 2012, is broadly consistent with administrative data on the number of cavity wall insulation measures installed under the CERT and ECO schemes.

72. Between April 2008 and December 2012, the CERT scheme delivered around 218,000 cavity and 9,000 solid and other wall insulation measures in Scotland^[21]. Between January 2013 and December 2018 a further 100,328 cavity and 59,828 solid wall insulation measures were delivered in Scotland by the successor ECO scheme^[22]. This equates to around 387,000 wall insulation measures, including around 318,000 cavity wall insulation measures, installed under these programs by the end of 2018. This is clearly reflected in the cumulative reduction of 316,000 uninsulated cavity wall dwellings reported by the SHCS since 2007 (Table 11).

73. Table 12 shows the levels of insulation in dwellings with solid or other construction type walls recorded by the survey in 2018. The results show that 19% of dwellings in this category had insulated walls in 2018; the difference with the level recorded in the previous year (18%) is not statistically significant but is an increase of 8 percentage points from 2012. Only 724 dwellings with solid walls were surveyed in 2018 as part of the SHCS. This relatively small sample does not allow enough precision to capture the increase in solid wall insulation measures which we know from administrative data is taking place. Since the beginning of January 2013 at least 59,828 solid wall insulation measures were delivered in Scotland^[23].

74. In the social sector, three quarters (75%) of cavity wall dwellings and around half (48%) of dwellings with solid and other wall types were estimated to have insulation in 2018. Nearly three-quarters (70%) of social housing overall had insulated walls.

75. In the private sector, nearly three quarters (72%) of cavity wall dwellings and more than one tenth (13%) of solid and other wall dwellings, had insulation in 2018. Over half (55%) of all private sector dwellings had insulated walls.

Table 12: Wall Insulation of Solid and Other Wall Types, 2012 and 2014 to 2018^[24]

	2018		2017		2016		2015		2014		2012
	000s	%	000s	%	000s	%	000s	%	000s	%	000s	%
Not insulated	524	81%	529	82%	524	85%	552	89%	528	86%	557	89%
Insulated	122	19%	115	18%	94	15%	71	11%	85	14%	66	11%
Total	646	100%	643	100%	617	100%	623	100%	613	100%	623	100%
Sample		724		718		696		655		663		711
Cumulative recorded installations under government schemes since 2007, thousands
CERT											9
ECO1	60		50		41		30		19

76. The information in Table 13 is broken down by type of cavity wall into hard to treat cavities (HTTC) and standard cavity walls using the ECO definition as far as possible with the available data (further details are available in section 7.11.6). HTTCs have certain attributes which make CWI more expensive, complex or inadvisable. Standard cavity walls have no such barriers.

77. 34% of cavity wall dwellings in Scotland have had retrofit cavity wall insulation, which is generally the lowest cost improvement available; the remainder of insulated cavity walls were insulated as built or insulated in another way.

78. Levels of insulation are higher in the social sector at 70% (all wall types) compared with 55% in the private sector. Within wall type, this tenure divide is also apparent for the more expensive insulation measures: internal / external insulation of cavity walls (15% of cavity wall dwellings in the social sector; 5% of private dwellings) and retrofit solid wall insulation measures (44% of solid wall dwellings in the social sector; 9% in the private sector).

79. No statistically significant improvements in wall insulation levels were recorded in the survey in the last year for either the private or the social housing sector. Low sample numbers mean the apparent decrease from 2017 in wall insulation amongst households in the social sector and the private sector are within the margin of error for the survey.

Table 13: Insulation by Wall Type and Tenure, 2018 and Insulation of all Wall Types by Tenure, 2017 and 2018^[25]

Wall and Insulation Type	Private Sector					Social Sector				Total
	000s	%type			%all	000s	%type		%all	000s	%type		%all
2018
Cavity
Un-insulated	361		28%	20%		139	25%	21%		500	27%	20%
- HTTC	113		9%	6%		54	10%	8%		167	9%	7%
-Standard	248		19%	14%		85	16%	13%		333	18%	13%
Insulated	924		72%	51%		407	75%	62%		1,331	73%	54%
-CWI	428		33%	23%		195	36%	30%		623	34%	25%
- Int/External	60		5%	3%		83	15%	13%		143	8%	6%
- As built	436		34%	24%		129	24%	20%		565	31%	23%
Total	1,285		100%	71%		546	100%	83%		1,831	100%	74%
Sample Size			1,617				623				2,240
Solid/Other
Un-insulated	467		87%	26%		57	52%	9%		524	81%	21%
- Pre-1919	402		75%	22%		29	26%	4%		431	67%	17%
- Post-1919	65		12%	4%		29	26%	4%		93	14%	4%
Insulated	70		13%	4%		52	48%	8%		122	19%	5%
- Retrofit	51		9%	3%		48	44%	7%		99	15%	4%
- As built	19		4%	1%		4	4%	1%		23	4%	1%
Total	537		100%	29%		109	100%	17%		646	100%	26%
Sample Size			614				110				724
All Wall Types
Uninsulated	828			45%		196		30%		1,024		41%
Insulated	994			55%		460		70%		1,453		59%
Total	1,822			100%		656		100%		2,477		100%
Sample Size				2,231				733				2,964
2017: All Wall Types
Uninsulated	811			44%		174		28%		986		40%
Insulated	1,026			56%		451		72%		1,478		60%
Total	1,838			100%		626		100%		2,464		100%
Sample Size				2,274				728				3,002

3.2 Boilers

Key Points

• In 2018, 62% of gas and oil boilers met the minimum efficiencies specified by the current Building Standards, an increase of 5 percentage points from 2017.

80. The heating system is a key factor in the thermal efficiency of a dwelling. Around 88% of households use a gas or oil-fuelled boiler. Trends in boiler efficiency are closely related to developments in energy efficiency and building standards regulations:

• From 1998, minimum boiler efficiency standards were set by European Council Directive 92/42/EEC^[26]
• In 2007, Scottish Building Standards increased the efficiency requirements for all new and replacement boilers^[27]

81. Building regulations in Scotland effectively require the installation of a condensing boiler^[28] for gas and oil-fuelled heating in new builds or when boilers are replaced in any dwelling.

82. The SHCS has recorded the age of the household’s heating system since 2010 and contains sufficient data to derive the Seasonal Efficiency (SEDBUK) ratings of surveyed boilers in the 2012-2018 data collections. For these years we can track the energy efficiency improvement of gas and oil boilers associated with the rising standards of the regulatory framework.

83. The methodology by which boiler efficiency ratings are calculated changed in 2016 and the time series was updated at that point to reflect this and to account for the minimum efficiency required of new oil combination condensing boilers. The data presented in Table 14 on the percentage of boilers compliant with standards is therefore comparable with the 2016 and 2017 Key Findings report but will not match data published in previous reports. Further details on the methodology change can be found in section 7.9.

84. The minimum requirements applied in the assessment of whether a boiler is compliant with standards are: a minimum efficiency of 88% for condensing standard gas, oil and LPG boilers; for condensing combination boilers, 86% for oil, and 88% for gas and LPG; for ranges, back boiler and combined primary storage units (CPSUs), 75% when gas, and 80% when oil^[29].

Table 14: Gas and Oil Boiler Improvements, 2010 & 2012-2018

	2018	2017	2016	2015	2014	2013	2012	2010
Households using gas or oil boilers for heating
%	88%	85%	86%	85%	84%	84%	82%	83%
000s	2,171	2,104	2,097	2,075	2,041	2,022	1,960	1,945
… of which
% "New" boilers (post-1998)	92%	91%	91%	89%	85%	83%	81%	70%
% condensing boilers	73%	67%	61%	56%	48%	43%	38%	22%
% standards compliant boilers	62%	57%	52%	47%	41%	33%	30%
Sample size (gas/oil boilers)	2,489	2,475	2,356	2,259	2,195	2,219	2,222	2,488

85. In 2018 the survey found that 92% of the domestic gas and oil boilers in Scotland had been installed since 1998, when the European Boiler Efficiency Directive minimum standards came into effect. The proportion installed since 1998 has increased by 22 percentage points since 2010.

86. In 2018, almost three-quarters (73%) of gas and oil boilers were condensing boilers. This represents a rapid increase of 5 percentage points since 2017 and 50 percentage points since 2010.

87. In 2018, 62% of gas and oil boilers met the minimum efficiencies specified by the current Building Standards, an increase of 5 percentage points from 2017. As older boilers reach the end of their life and are replaced, we expect to see a continuation of this trend of improving efficiency.

3.3 Energy Performance Certificates

Key Points

• In 2018, 43% of Scottish homes were rated as EPC band C or better under 2012 ( v9.93) (the first year in which data for this version of is available).

• Under SAP 2012 (RdSAP v9.92), 44% of Scottish homes were rated as EPC band C or better in 2018, similar to the previous year but up from 39% in 2016 and from 35% in 2014 (the first year in which data based on SAP 2012 is available).

• Under SAP 2009, which allows comparisons over a longer period, almost half of dwellings (49%) were rated C or better, up 25 percentage points since 2010. In the same period, the proportion of properties in the lowest EPC bands (E, F or G) has more than halved, reducing from 27% in 2010 to 12% in 2018.

88. Energy Performance Certificates (EPC)^[30] were introduced in January 2009 under the requirements of the EU Energy Performance Building Directive (EPBD). They provide energy efficiency and environmental impact ratings for buildings based on standardized usage. EPCs are required when a property is either sold or rented to a new tenant.

89. EPCs are generated through the use of a standard calculation methodology, known as Standard Assessment Procedure (SAP). SAP is the UK Government approved way of assessing the energy performance of a dwelling, taking into account the energy needed for space and water heating, ventilation and lighting and, where relevant, energy generated by renewables.

90. The Energy Efficiency Rating (EER) is expressed on a scale of 1-100 where a dwelling with a rating of 1 will have very poor energy efficiency and higher fuel bills, while 100 represents very high energy efficiency and lower fuel bills. Ratings can exceed 100 where the dwelling generates more energy than it uses.

91. Ratings are adjusted for floor area so that they are essentially independent of dwelling size for a given built form.

92. For Energy Performance Certificates EERs are presented over 7 bands, labelled A to G. Band A represents low energy cost and high energy efficiency, while band G denotes high energy cost (and low energy efficiency).

93. Energy Efficiency Ratings reported in this publication are calculated under two versions of SAP, the SAP 2009 methodology^[31] and the SAP 2012 methodology^[32]. Using SAP 2009 enables us to examine the trend in the energy efficiency of the housing stock since 2010. SAP 2012 was first used in reporting data from the SHCS in the 2014 Key Findings report and therefore only four years of data are available.

94. SAP is periodically reviewed by the UK government to ensure it remains fit for purpose and to address its continued application across an increasing range of carbon and energy reduction policy areas. SAP is used for assessment of new buildings whilst a ‘reduced data’ version of the methodology, RdSAP, is applied to assessment of existing buildings.

95. SHCS energy modelling for SAP 2012 is currently based on RdSAP (v9.92) which was released on 7 December 2014. This introduced some technical updates and broadening of scope (for example, enabling assessment of ‘park homes’ as a dwelling type) as well as updating UK carbon factors and fuel costs based upon recent research undertaken by the Department for Business, Energy and Industrial Strategy (BEIS).

96. The latest version of RdSAP (v9.93)^[33] was released on 19 November 2017 and contains revisions to the underlying assumptions used within the SAP calculations. The most notable update to the methodology in v9.93 was a change to the default U-values of cavity, solid and stone walls, built prior to 1976. These U-values are used to calculate the rate of heat loss through the walls, which contributes to the overall thermal performance of the building fabric of the dwelling. RdSAP v9.93 has been applied for the first time in this publication. Prior to the 2018 Key Findings report, the SAP 2012 methodology was aligned to RdSAP v9.92. To allow analysis of the effect of this update, 2018 EERs have been described in this report based on SAP 2012 under both RdSAP versions.

3.3.1 Energy Efficiency Rating, SAP 2009

97. Table 15 shows the trend in mean EERs based on SAP 2009, which rose from 59.9 in 2010 to 66.1 in 2018. These ratings fall into band D. There was around a 1 point increase in the mean EER each year between 2010 and 2014. Improvement since then has been slower, and the increase between 2017 and 2018 was less than 1% which is not statistically significant.

Table 15: Average EER for 2010 – 2018, SAP 2009

		2018	2017	2016	2015	2014	2013	2012	2011	2010
EER	Mean	66.1	65.6	65.1	64.6	64.1	63.2	61.8	60.9	59.9
	Median	68	68	67	67	67	66	64	63	62
Sample		2964	3002	2850	2754	2682	2725	2787	3219	3115

98. The median EE Rating has also improved since 2010. In 2018 half of all Scottish dwellings were rated 68 or better, an increase from 62 in 2010 (Figure 10). Both ratings fall into band D.

Figure 10: Median EER relative to EPC bands, SAP 2009, 2010-2018

99. The average figures reflect that Scottish housing is gradually moving up through the EPC bands, as shown in Figure 11 and Table 16.

Figure 11: Distribution of the Scottish Housing Stock by EPC Band, SAP 2009, 2012-2018

Note: Values for this figure are provided in Table 16.

100. Almost half (49%) of the housing stock in 2018 had an EPC rating of C or better, up 25 percentage points since 2010 (Table 16). Over the same period, the proportion of properties in the lowest EPC bands, E, F and G, has dropped 16 percentage points: 27% of properties were rated E, F or G in 2010 compared with 12% in 2018.

Table 16: Distribution of the Scottish Housing Stock by EPC Band, SAP 2009, 2010 and 2014 to 2018

EPC band	2018		2017		2016		2015		2014		2010
	000s	%	000s	%	000s	%	000s	%	000s	%	000s	%
A (92-100)	-	-	-	-	-	-	-	-	-	-	-	-
B (81-91)	70	3%	69	3%	54	2%	62	3%	42	2%	18	1%
C (69-80)	1,140	46%	1,072	44%	989	40%	953	39%	939	39%	547	23%
D (55-68)	971	39%	1,012	41%	1,070	44%	1,055	43%	1,037	43%	1,157	49%
E (39-54)	232	9%	240	10%	279	11%	298	12%	321	13%	495	21%
F (21-38)	57	2%	63	3%	56	2%	59	2%	68	3%	127	5%
G (1-20)	8	0%	8	0%	5	0%	7	0%	14	1%	13	1%
Total	2,477	100%	2,464	100%	2,452	100%	2,434	100%	2,420	100%	2,368	100%
Sample		2964		3002		2850		2754		2682		3115

No A-rated properties were sampled between 2010 and 2018.

3.3.2 Energy Efficiency Rating, SAP 2012

101. This section examines the energy efficiency profile of the Scottish housing stock in 2018 under the most recent SAP 2012 methodology^[34]. Time series analysis includes 2018 data for both SAP 2012 (RdSAP v9.93) and SAP 2012 (RdSAP v9.92). Breakdown analysis of 2018 data is presented under the updated methodology alone: SAP 2012 (RdSAP v9.93).

102. Dwellings with main heating fuels other than mains gas (for example oil or coal) have systematically lower SAP ratings in SAP 2012 than in SAP 2009 and this is particularly true at the lower end of the SAP range. The main reason for this is that between SAP versions 2009 and 2012, fuel prices for these fuels increased more than for mains gas. As a result, average EERs tend to be slightly lower under SAP 2012 compared to SAP 2009.

103. Table 17 and Table 18 show the energy efficiency profile of the Scottish housing stock between 2014 and 2018 under SAP 2012. Figure 12 shows this alongside the longer term change as measured by SAP 2009.

Table 17: Average EER for 2014-2018, SAP 2012 (RdSAP v9.92) and 2018, SAP 2012 (RdSAP v9.93)

		2018	2017	2016	2015	2014
EER (RdSAP v9.92)	Mean	64.8	64.3	63.7	62.8	62.2
	Median	67	67	66	65	65
EER (RdSAP v9.93)	Mean	64.7
	Median	67
Sample		2,964	3,002	2,850	2,754	2,682

104. In 2018, the mean energy efficiency rating of the Scottish housing stock under SAP 2012 (RdSAP v9.93) was 64.7 and the median was 67 points, indicating that half of the housing stock has an energy efficiency rating of 67 or better (Table 17).

105. In 2018, the mean energy efficiency rating of the Scottish housing stock under SAP 2012 (RdSAP v9.92) was 64.8 and the median was 67 points. The difference in mean rating between 2017 and 2018 was not significant. However, there has been an overall improvement since 2014.

106. Over two-fifths (43%) of all properties in 2018 were rated C or better under SAP 2012 (RdSAP v9.93) (Table 18). Less than a fifth (15%) were in bands E, F or G.

107. More than two-fifths (44%) of all properties in 2018 were rated C or better under SAP 2012 (RdSAP v9.92), similar to 2017 but an increase from 35% in 2014. Less than a fifth (15%) were in bands E, F or G – a drop of 6 percentage points over the 5-year period from 2014 to 2018.

108. The update to the underlying methodology had little effect in 2018. Both the mean and median EERs were similar for SAP 2012 (RdSAP v9.92) and SAP 2012 (RdSAP v9.93). Similarly, the distribution of the Scottish housing stock across EPC bands were similar for SAP 2012 (RdSAP v9.92) and SAP 2012 (RdSAP v9.93).

Table 18: Distribution of the Scottish Housing Stock by EPC Band, 2014-2018, SAP 2012 (RdSAP v9.92) and 2018, SAP 2012 (RdSAP v9.93)

	RdSAP v9.93		RdSAP v9.92
EPC Band	2018		2018		2017		2016		2015		2014
	000s	%	000s	%	000s	%	000s	%	000s	%	000s	%
A (92-100)	-	-	-	-	-	-	-	-	-	-	-	-
B (81-91)	68	3%	71	3%	65	3%	53	2%	53	2%	29	1%
C (69-80)	989	40%	1,028	41%	978	40%	910	37%	837	34%	830	34%
D (55-68)	1,039	42%	1,000	40%	1,028	42%	1,068	44%	1,061	44%	1,052	43%
E (39-54)	282	11%	277	11%	280	11%	321	13%	368	15%	369	15%
F (21-38)	83	3%	83	3%	95	4%	88	4%	94	4%	115	5%
G (1-20)	17	1%	18	1%	18	1%	13	1%	20	1%	25	1%
Total	2,477	100%	2,477	100%	2,464	100%	2,452	100%	2,434	100%	2,420	100%
Sample		2,964		2,964		3,002		2,850		2,754		2,682

No A-rated properties were sampled for 2014-2018

109. Figure 12 shows EPC bandings for SAP 2009 and SAP 2012 (RdSAP v9.92 and RdSAP v9.93). The chart shows a strong trend of improvement in the energy efficiency profile of the housing stock since 2010. The proportion of dwellings rated C or better increased from 24% in 2010 to 49% in 2018 (as measured under SAP 2009), and 35% in 2014 to 44% in 2018 (as measured under SAP 2012 (RdSAP v9.92)).

Figure 12: Grouped EPC Bands under SAP 2009, SAP 2012 (RdSAP v9.92) and SAP 2012 (RdSAP v9.93), 2010-2018

110. Table 19 shows the energy efficiency profile by broad tenure groups in 2018 using SAP 2012 (RdSAP v9.93). Figure 13 provides more details on the distribution of the least energy efficient properties by household characteristics.

Table 19: EPC Band by Broad Tenure in 2018, SAP 2012 (RdSAP v9.93)

EPC Band	Owner occupied		Private rented		Social sector		All Tenures
	000s	%	000s	%	000s	%	000s	%
A (92-100)	-	-	-	-	-	-	-	-
B (81-91)	38	2%	10	4%	19	3%	68	3%
C (69-80)	547	35%	109	40%	333	51%	989	40%
D (55-68)	694	45%	86	31%	260	40%	1,039	42%
E (39-54)	205	13%	42	16%	35	5%	282	11%
F & G (1-38)	65	4%	26	10%	9	1%	100	4%
Total	1,548	100%	273	100%	656	100%	2,477	100%
Sample		1,937		294		733		2,964

111. Over half (54%) of social housing is in band C or better under SAP 2012, compared to just over two-fifths (44%) in the private rented sector and 38% of owner-occupied households. 7 per cent of dwellings in the social sector are within EPC bands E, F or G, while 17% of owner occupied dwellings and 25% of the private rented sector are within these EPC bands. Housing in the social sector tends to be more energy efficient than the owner occupied or private rented sector. This could be driven by the Scottish Housing Quality Standard and the Energy Efficiency Standard for Social Housing which introduced minimum energy efficiency levels for that sector.

112. Figure 13 shows that the share of dwellings in the lowest energy efficiency bands (F and G) is particularly high for pre-1919 dwellings (14%), non-gas heated properties (between 13% and 25%), detached properties (10%) and in the private rented stock (10%). Across Scotland as a whole, 4% of properties were in bands F or G in 2018.

Figure 13: Proportion of Homes in Band F or G by Dwelling Age, Primary Heating Fuel, Tenure and Household and Dwelling Type in 2018 (SAP 2012 (RdSAP v9.93))

Base figures and more detailed breakdowns are provided in Table 20 and Table 21.

113. More detailed 2018 breakdowns are shown in Table 20 by household characteristics.

114. Mean SAP 2012 (RdSAP v9.93) ratings ranged from 62.3 in owned-outright dwellings to 70.3 in housing association dwellings, a statistically significant difference. Social housing as a whole is more energy efficient than the private sector, with a mean EER of 68.0 compared to 63.5 for private dwellings.

115. Older households (63.2) have higher average EER ratings than families (66.1) and other (adults without children) households (65.0).

116. Mean EER ratings were similar across all income bands and ranged from 64.2 to 65.7. Similarly, average EER ratings were similar across council tax bands and ranged from 63.0 to 65.3.

Table 20: Mean EER and Broad EPC Band, by Household Characteristics in 2018, SAP 2012 (RdSAP v9.93)

	EE Rating	Band			Sample
	Mean	BC	DE	FG
Tenure
Owned outright	62.3	33%	62%	5%	1,091
Mortgaged	65.3	44%	53%	3%	846
LA/Other public	66.6	45%	54%	1%	459
HA/co-op	70.3	68%	31%	1%	274
PRS	62.4	44%	47%	10%	294
Private	63.5	39%	56%	5%	2,231
Social	68.0	54%	45%	1%	733
Household Composition
Older Households	63.2	36%	59%	5%	974
Families	66.1	47%	51%	3%	667
Other households	65.0	45%	51%	4%	1,323
Weekly Household Income
< £200	64.9	39%	57%	4%	281
£200-300	64.2	43%	53%	4%	480
£300-400	65.7	48%	48%	4%	464
£400-500	64.9	39%	57%	4%	344
£500-700	64.2	42%	55%	4%	506
£700+	64.2	43%	52%	5%	830
Council Tax Band
Band A	65.1	46%	51%	4%	597
Band B	64.8	38%	59%	3%	659
Band C	65.3	46%	49%	4%	490
Band D	64.7	45%	51%	4%	392
Band E	64.5	41%	55%	4%	395
Band F	63.4	40%	53%	7%	275
Band G & H	63.0	41%	54%	5%	156
Scotland	64.7	43%	53%	4%	2964

117. Table 21 shows that there is a strong association between dwelling characteristics and energy efficiency rating. Across dwelling types, detached properties have the lowest energy efficiency profile on average (mean EER 60.9) while flats have the highest rating (69.1 for tenements and 67.1 for other flats).

118. The oldest, pre-1919, properties are least energy efficient (mean EER of 55.3 and only 20% rated C or better) while those built after 1982 have the highest energy efficiency ratings (mean EER of 71.7, with 74% in band C or better).

119. Primary heating fuel is a key determinant of the energy efficiency of the dwelling. Properties heated by mains gas have an average rating of 67.0 and 47% are in band C or better. Dwellings heated by other fuels (including electric and oil) have considerably lower ratings. The average energy efficiency rating for oil heated properties is 47.7 (making the average dwelling in this group E rated) and only 4% are in band C or better.

120. Proximity to the gas grid has a similar effect on the energy efficiency rating (average SAP rating 66.1 for dwellings near the gas grid, higher than the 58.1 for other dwellings).

121. As dwelling characteristics associated with lower energy efficiency are disproportionately represented in rural areas, the average energy efficiency profile of rural properties is lower than that for urban; Table 21 shows that mean SAP 2012 rating is 66.6 for dwellings in urban areas, higher than the 54.8 for dwellings in rural areas .

122. Due to the change in the underlying SAP 2012 methodology, data for 2018 is not comparable to data from 2017 therefore improvements since 2017 have not been presented.

Table 21: SAP 2012 (RdSAP v9.93): Mean EER and Broad EPC Band, by Dwelling Characteristics, 2018

	EE Rating		Band					Sample
	Mean		BC		DE		FG
Dwelling Type
Detached	60.9		37%		53%		10%	807
Semi	62.7		28%		70%		2%	659
Terraced	64.2		36%		61%		3%	633
Tenement	69.1		62%		37%		2%	514
Other flats	67.1		52%		46%		2%	351
Age of dwelling
pre-1919	55.3		20%		65%		14%	521
1919-1944	63.1		26%		71%		2%	327
1945-1964	64.7		36%		61%		3%	654
1965-1982	64.8		39%		60%		2%	654
post-1982	71.7		74%		26%		0%	808
Primary Heating Fuel
Gas	67.0		47%		52%		1%	2,233
Oil	47.7		4%		71%		25%	259
Electric	56.5		26%		62%		13%	396
Other	58.5		49%		29%		22%	75
Location
urban	66.6		47%		52%		2%	2,292
rural	54.8		21%		62%		16%	672
Gas Grid
On	66.1		44%		55%		1%	2,239
Off	58.1		38%		47%		16%	725
Scotland	64.7		43%		53%		4%	2,964

Note: There was one N/A response for Primary Heating Fuel which has been excluded from the table but included in the Scotland statistics.

3.4 National Home Energy Ratings (NHER)

123. The National Home Energy Ratings (NHER) system was the main methodology used in the SHCS to report on the energy efficiency of the housing stock prior to 2013. With the publication of the 2013 SHCS Key Findings Report the energy modelling methodology was updated and it is no longer possible to reproduce exactly the original NHER method, as the full documentation of this method is not publicly available. However because of user interest and because NHER scores are taken into account under the energy efficiency criterion of the SHQS, we provide an approximate NHER score. Further details can be found in the Methodology Notes to the 2013 SHCS report^[35].

124. Table 22 presents banded NHER scores and mean values for selected categories of dwellings and household types for 2018. Significant differences were seen by age of dwelling, with older dwellings having lower average values (6.2 for pre-1919) than properties that were built more recently (8.7 for post-1982). Private sector dwellings had significantly lower NHER scores (7.4) than social sector (8.2) with mean scores by detailed tenure ranging from 7.2 (owned outright) to 8.6 (housing associations). There were also differences by dwelling type ranging from detached properties at 7.1 to tenements at 8.4. Dwellings using oil as their main fuel had the lowest score at 5.5 while those fuelled by gas had the highest at 7.9.

125. Table 22 also shows the percentage of homes in each dwelling and household category that were rated as good, moderate, or poor. Significant differences in the percentage of dwellings that were rated as “good” were seen by type of dwelling (66% of detached properties, compared to 86% of tenement flats) and age of dwelling (48% of pre-1919 dwelling, lower than 93% of post-1982 dwellings). Primary heating fuel also had an impact on the proportion that were rated as good (84% of dwellings with gas as a primary fuel, compared to just 35% of dwellings with oil as a primary fuel). This profile is similar to SAP 2012 (RdSAP v9.93).

Table 22: NHER Scores and Banded Ratings by Selected Dwelling and Household Characteristics, 2018

		Mean	NHER band			Sample
			Good	Moderate	Poor
Scotland		7.6	77%	22%	2%	2,964
Dwelling Type (grouped)
Detached		7.1	66%	30%	4%	807
Semi-detached		7.2	71%	29%	0%	659
Terraced		7.4	78%	21%	1%	633
Tenement		8.4	86%	13%	2%	514
Other flats		8.0	85%	14%	1%	351
Age of dwelling
pre-1919		6.2	48%	46%	6%	521
1919-1944		7.3	77%	22%	1%	327
1945-1964		7.6	79%	19%	1%	654
1965-1982		7.6	79%	20%	0%	654
post 1982		8.7	93%	*	*	808
Primary Heating Fuel
Gas		7.9	84%	16%	0%	2,233
Oil		5.5	35%	58%	8%	259
Electric		6.1	43%	48%	9%	396
Other fuel type		7.2	60%	36%	4%	75
Tenure
Owned outright		7.2	70%	28%	2%	1,091
Mortgaged		7.6	78%	22%	1%	846
LA		7.9	85%	15%	1%	459
HA		8.6	89%	9%	1%	274
Private rented		7.3	71%	25%	4%	294
Private Sector		7.4	73%	25%	2%	2,231
Social Sector		8.2	86%	13%	1%	733
Household Composition
Older Households		7.4	72%	26%	2%	974
Families		7.7	80%	19%	0%	667
Other Households		7.7	78%	20%	2%	1,323

Note: There was one N/A response for Primary Heating Fuel which has been excluded from the table but included in the Scotland statistics.

3.5 Carbon Emissions

Key Points

• Based on modelled energy use, the average Scottish home is estimated to produce 6.8 tonnes of CO2 per year in 2018, which is almost double the average carbon emissions per household as reported by BEIS (3.6 tonnes per year) in 2017, based on actual energy use. This suggests that households are not heating their homes to the standard heating regimes.
• Average modelled carbon emissions for all properties have continued to decrease to 73 kg/m2 in 2018 compared to 80 kg/m2 in 2014.

126. Carbon Emissions are the amount of greenhouse gas emissions, expressed as their carbon dioxide gas equivalent, vented to the atmosphere. Estimates of emissions from the residential sector which take into account actual energy consumption by households are reported by BEIS at Local Authority and Scotland level annually^[36]. This methodology is consistent with the Greenhouse Gas Inventory (GHGI) which is the source for monitoring progress against the Scottish Government’s climate change commitments.

127. In contrast, emissions reported from the SHCS are modelled on the assumption of a standard pattern of domestic energy consumption and do not reflect differences in consumption behaviour due to preferences or changes in weather conditions. As such, they are distinct from the carbon emissions figures published by BEIS and compiled in GHG inventories.

128. Table 23 shows modelled emissions from the SHCS and provides a comparison with the estimates published by BEIS for the period 2012-2017.

129. In 2012, cooler temperatures led to an increase in domestic energy consumption and an increase in CO2 emissions from the domestic sector overall. This was reflected in the estimates of emissions levels from the domestic sector reported by BEIS. At the same time, modelled SHCS emissions per household fell by 1.4%, reflecting the improved energy efficiency of the sector in this period and the greater potential to reduce CO2 emissions. Average carbon emissions per household have decreased year on year since 2013, accompanied by a decrease in the SHCS based average modelled emissions, with the exception of 2014. However, there was a methodology change from 2014 so the modelled emissions figures between 2013 and 2014 are not fully comparable^[37]. The SHCS estimates are not designed to capture the increased demand for heating due to colder weather or reduced demand associated with warmer weather in any particular year.

Table 23: Carbon Emissions and Modelled Emissions in Scottish Housing, 2012-2018

		2018	2017	2016	2015	2014	2013	2012
Carbon Emissions1: BEIS Domestic sector	Total (Mtonnes)		8.8	9.5	10.0	10.4	12.3	12.7
	per HH (tonnes) 2		3.6	3.9	4.1	4.3	5.1	5.3
	% change per HH		-7.5%	-6.0%	-4.7%	-15.7%	-4.0%	5.9%
Modelled emissions: SHCS	Total (“Mt”)	16.8	17.3	17.2	17.7	17.9	17.4	18.1
	per HH (“t”)	6.8	7.0	7.0	7.3	7.4	7.3	7.6
	% change per HH	-3.4%	-3.2%	-3.0%	-1.8%	1.1%	-3.6%	-1.4%

1 Local and Regional CO2 Emissions Estimates, BEIS. Data reflects revisions made in the most recent publication. https://www.gov.uk/government/statistics/uk-local-authority-and-regional-carbon-dioxide-emissions-national-statistics-2005-2017

2 Number of households (HHs) sourced from National Records of Scotland, Estimates of Households and Dwellings, 2017: https://www.nrscotland.gov.uk/statistics-and-data/statistics/statistics-by-theme/households/household-estimates/2018

*Modelled emissions figures for 2014-2018 are not fully comparable to the previous years.

130. Estimates in the Third Report on Proposals and Policies (RPP3)^[38] or in the Climate Change Plan^[39] are also not comparable to SHCS estimates. RPP3 figures for the residential sector relate to non-traded emissions only (i.e. exclude electricity which is covered by the EU Emissions Trading System) while SHCS estimates cover all fuel types.

131. This report is only concerned with the level and variations in modelled emissions from the Scottish housing stock. These estimates are produced through the use of BREDEM 2012-based models, in line with other statistics on energy efficiency and fuel poverty reported here^[40].

132. To derive emissions estimates, modelled energy demand is combined with carbon intensity factors as adopted for the 2012 edition of the SAP (see section 7.3). These are CO2 equivalent figures which include the global warming impact of CH4 and N2O as well as CO2.

133. The change in the underlying BREDEM 2012 model, first implemented in the reporting of 2014 data, has meant that carbon emissions for 2014-2018 are not estimated on a consistent basis with those for 2010-2013. Further details on this change are given in the Methodology Notes to the 2014 Key Findings report^[41].

3.5.1 Modelled Emissions by Dwelling Type and Age of Construction

134. The annual modelled emissions from a property reflect the energy use for the whole dwelling heated according to the standard heating regime^[42]. Figure 14 shows that dwellings with larger floor area generally have higher carbon emissions.

135. Newer dwellings have lower modelled emissions than older ones on average as a result of their better thermal performance and higher energy efficiency (as shown in section 3.3). Post-1982 flats have the lowest modelled emissions on average; less than 4 tonnes per year (Table 24).

Figure 14: Average Floor Area and Average Modelled Annual Emissions by Age and Type of Dwelling, 2018

Note: Floor areas for these subgroups are provided in section 2.1.1. Modelled carbon emissions figures are provided in Table 24.

The black line indicates the average modelled emissions for the dwelling age group.

Table 24: Average Modelled Annual Carbon Emissions (tonnes per year) by Dwelling Age and Type, 2018

Dwelling Type	Dwelling Age
	Pre-1919	1919-1982	Post-1982	All
Detached	15.8	10.1	8.1	10.2
Semi-detached	12.0	7.1	5.2	7.1
Terraced	10.8	5.9	4.7	6.4
Tenement	5.7	4.1	3.4	4.4
Other flats	7.8	4.8	3.7	5.2
All dwelling types	9.7	6.3	5.7	6.8

136. Across all age bands, detached houses have the highest modelled emissions due to a larger share of exposed surfaces. As shown in section 2.3, they are also the most likely to use high carbon-intensity fuels such as oil and coal in place of mains gas.

137. By dividing modelled emissions by total internal floor area we derive emissions per square meter (kg/m2). Controlling for floor area in this way shows that pre-1919 detached houses have the highest modelled emissions per sq. m (112 kg/m² ), as shown in Table 25. Post-1982 detached dwellings (58 kg/m2), tenements (57 kg/m2) and other flats (60 kg/m2) have the lowest emissions.

Table 25: Average Modelled Emissions per Square Meter of Floor Area (kg/m2) by Age and Type of Dwelling, 2018

Dwelling Age		Pre-1919	1919-1982	Post-1982	All Ages
Type	Detached	112	78	58	75
	Semi	103	78	64	77
	Terraced	97	73	59	74
	Tenement	83	67	57	69
	Other flats	80	68	60	70
All types		94	73	59	73

3.5.2 Modelled Emissions by Tenure

138. Although data for 2014-2018 is not directly comparable to prior years, the data suggests that there is a longer term trend of declining emissions. Average modelled carbon emissions reduced from 92 kg/m2 in 2010 to 80 kg/m2 in 2013. Based on the updated carbon emissions methodology, there was then a further decrease from 80 kg/m2 in 2014 to 73 kg/m2 in 2018.

139. Table 26 and Figure 15show how emissions differ across tenure for the period 2010-2018. The highest rates of emissions were observed for private rented dwellings (82 kg/m2) and lowest for housing association dwellings (66 kg/m2), with emissions from the other tenures falling in between those values. The values were similar to the previous year across all tenures, however the longer time series shows a decreasing trend over the 2010-2018 period for all tenures.

140. Changes to the tenure definitions and the revised carbon emissions methodology mean that figures for 2014-2018 by tenure are not fully comparable to earlier years. Differences that were statistically significant were seen in the mortgaged sector (reducing from 78 kg/m2 in 2014 to 70 kg/m2 in 2018) and households that are owned outright (reducing from 81 kg/m2 to 75 kg/m2 between 2014 and 2018).

Table 26: Average Modelled Emissions per Square Meter by Tenure, 2010, 2013, 2014-2018

	2018	2017	2016	2015	2014	2013	2012	2011	2010
Owned outright	75	75	78	79	81	81	94	92	98
Mortgaged	70	70	73	74	78	79	85	90	90
LA/Other public	73	74	76	78	77	79	82	84	89
HA/co-op	66	68	66	70	71	70	79	79	79
PRS	82	83	86	87	89	90	93	100	101
All Tenures	73	74	76	78	80	80	88	90	92

Data prior to 2014 does not include households living rent free. Figures for 2014-2018 are therefore not fully comparable to the previous years.

Figure 15: Modelled Emission per square meter (kg/m2) by Tenure, 2010-2018

Data prior to 2014 does not include households living rent free. Figures for 2014-2018 are therefore not fully comparable to previous years.

3.6 Environmental Impact Rating

141. The Environmental Impact Rating (EIR) represents the environmental impact of a dwelling in terms of carbon emissions associated with fuels used for heating, hot water, lighting and ventilation. Ratings are adjusted for floor area so they are independent of dwelling size for a given built form. Emissions for this measure are calculated using SAP methodology.

142. The latest version of RdSAP (v9.93)^[43] was released on 19 November 2017 and contains revisions to the underlying assumptions used within the SAP calculations. RdSAP v9.93 has been applied for the first time in this publication. Prior to the 2018 Key Findings report, the SAP 2012 methodology was aligned to RdSAP v9.92. To allow analysis of the effect of this update, 2018 EIs have been described in this report based on SAP 2012 under both RdSAP versions.

143. EI ratings for 2015-2018, produced on the basis of SAP 2012, are not fully comparable to those for the period 2010-2013, which were produced on the basis of SAP 2009.

144. Figure 16 illustrates the increasing trend in the median EIR between 2010 and 2018. This indicates that the environmental impact of Scottish housing is gradually falling over time.

145. The update to RdSAP v9.93 in SAP 2012 had no effect on the median EIR in 2018 which was similar for both SAP 2012 versions.

Figure 16: Median EIR relative to Band, 2010-2013 (SAP 2009), 2015-2018 (SAP 2012 (RdSAP v9.92)) and 2018 (SAP 2012 (RdSAP v9.93))

146. As shown in Table 27, 33% of dwellings had EI ratings in band C or better under SAP 2012 (RdSAP v9.93) in 2018. The mean rating was 61 and the median was 63, both of which fall in band D.

147. Under SAP 2012 (RdSAP v9.92) 34% of dwellings had EI ratings in band C or better, an improvement on the 2017 figure of 32%. The mean rating was 61 and the median was 64, both of which fall in band D.

148. In 2018, 8% of dwellings were rated F or G in terms of their environmental impact under both SAP 2012 versions.

Table 27: EIR Bands in the Scottish Housing Stock, 2012-2013 and 2016-2018 SAP 2012 (RdSAP v9.92) and 2018 SAP 2012 (RdSAP v9.93)

	RdSAP v9.93		RdSAP v9.92
EPC Band	2018		2018		2017		2016		2013		2012
	000s	%	000s	%	000s	%	000s	%	000s	%	000s	%
A - B (81+)	125	5%	136	6%	120	5%	96	4%	79	3%	71	3%
C (69-80)	682	28%	709	29%	671	27%	613	25%	683	29%	524	22%
D (55-68)	993	40%	952	38%	929	38%	947	39%	895	37%	888	37%
E (39-54)	473	19%	476	19%	512	21%	558	23%	509	21%	587	25%
F (21-38)	171	7%	170	7%	191	8%	200	8%	197	8%	248	10%
G (1-20)	34	1%	34	1%	41	2%	39	2%	38	2%	64	3%
Total	2,477	100%	2,477	100%	2,464	100%	2,452	100%	2,402	100%	2,383	100%
Mean		61		61		60		59		60		57
Median		63		64		63		62		63		60
Sample		2,964		2,964		3,002		2,850		2,725		2,783

Data prior to 2014 does not include households living rent free. Figures for 2014-2018 are therefore not fully comparable to previous years.

149. Figure 17 illustrates that the energy efficiency and the environmental impact rating for the median Scottish dwelling have changed in parallel since 2010.

Figure 17: Trend in Median EE and EI Ratings, 2010-2013 and 2015-2018

150. Table 28 shows how EI ratings vary across different type of dwellings. As expected dwellings built since 1982 have better environmental impact ratings than other dwellings, with 60% rated C or better and only 2% in the bottom two bands (F and G). Flats have a lower environmental impact (higher EI rating) than houses, as do gas heated properties compared to those using oil or electricity.

151. Oil heating systems and houses are more common in rural areas, leading to lower overall environmental impact ratings for rural dwellings.

Table 28: SAP 2012 (RdSAP v9.93): Mean EIR and Broad EIR Band, by Dwelling Characteristics, 2018

	Environmental Impact Rating			EI Band						Sample
	Mean			ABC		DE		FG
Dwelling Type
Detached	56.1			24%		61%		15%		807
Semi-detached	57.5			17%		74%		9%		659
Terraced	60.1			28%		64%		8%		633
Tenement	67.1			54%		42%		4%		514
Other flats	64.2			40%		56%		4%		351
Age of Dwelling
pre-1919	50.0			14%		62%		23%		521
1919-1944	58.7			19%		75%		6%		327
1945-1964	61.1			26%		68%		6%		654
1965-1982	60.5			28%		66%		7%		654
post-1982	69.4			60%		39%		2%		808
Primary Heating Fuel
Gas	64.0		37%			61%		2%		2,233
Oil	39.6		*			52%		*		259
Electric	46.6		6%			60%		34%		396
Other fuel type	65.8		*			15%		*		75
Urban-Rural Indicator
Urban	63.0		36%			60%		4%		2,292
Rural	50.0		16%			56%		28%		672
Gas Grid
On	62.3		32%			64%		4%		2,239
Off	54.4		34%			38%		27%		725
Scotland	60.8		33%			59%		8%		2,964

Note: There was one N/A response for Primary Heating Fuel which has been excluded from the table but included in the Scotland statistics.