Scottish House Condition Survey: Key Findings 2011

3 Energy Efficiency

19. The overall energy use of a household depends on the energy efficiency of the dwelling plus the behaviour of the occupants. The SHCS does not record the behaviour of occupants but concentrates on the energy efficiency of the dwelling. However it does ask respondents to what extent they monitor their energy use (see section 3.1).

20. The energy efficiency of a dwelling depends on its physical characteristics. Factors such as the age of dwelling, the type of dwelling and the extent of loft and wall insulation all affect the efficiency. The efficiency of the boiler and the type of fuel used for space and water heating, as well as cooking are also factors.

21. Energy efficiency is measured using two methodologies: the National Home Energy Rating (NHER) and the UK Government's Standard Assessment Procedure for the Energy Rating of Dwellings (SAP, 2005 ). The NHER considers all energy use in the home including cooking and electrical appliances and allows for regional and geographic climate variations. The SAP considers energy used by space heating (with auxiliary equipment) and hot water and lighting (under SAP 2005), and uses a single UK climate source in East Yorkshire. Both measures are modelled using standard heating regimes and do not take into account the behaviours of individual households.

22. In this chapter we report on analysis of:

• levels of insulation in Scottish dwellings (section 3.2)
• NHER (section 3.3) and SAP (2005) (section 3.4) ratings
• results obtained by approximating the Energy Performance Certificates Energy Efficiency Ratings (EPC EER) methodology using SHCS data (section 3.5)
• modelled CO₂ emissions from dwellings (section 3.6)

3.1 Monitoring Energy Use

23. Since 2008 the SHCS has asked respondents to what extent they monitor the energy use in their property. Table 5 shows responses to this question. Since 2008 there has been very little variation.

24. In 2011, about 33% of households said they monitor their energy use fairly closely and 14% said they monitor it very closely. Figure 2 shows the extent of energy monitoring by net weekly household income band. It shows that there is little difference between income bands - with around 50% of each income band monitoring their energy use either very or fairly closely.

Table 5 Extent to which energy use is monitored, 2008 to 2011 (%)

Extent energy use is monitored	2008	2009	2010	2011
Very closely	11	13	12	14
Fairly closely	33	34	33	33
Not very closely	24	25	23	22
Not at all	31	28	32	30
Don't know	1	0	0	0
Total	100	100	100	100
Unweighted total	3,762	4,153	3,853	3,949

Source: Continuous SHCS

Figure 2 Extent to which energy use is monitored within property by net weekly household income band (%)

Source: SHCS 2011

25. Although the extent to which householders monitor their energy use has not changed a great deal over the period 2008 to 2011, the prevalence of energy monitoring devices has continued to rise steadily. Table 6 shows the growing prevalence of energy monitoring devices - an additional 120,000 since 2008 representing 7% of all households in Scotland.

Table 6 Energy-use monitoring devices, 2008 to 2011 (000s and %)

Year		Do you have an energy-use monitoring device in your home?				Sample Size
		Yes	No	Don't know	Total
2008	000s	37	2,286	8	2,331	3,762
	%	2	98	0	100	0
2009	000s	54	2,285	6	2,344	4,153
	%	3	97	0	100	0
2010	000s	101	2,254	3	2,357	3,853
	%	4	96	0	100	0
2011	000s	155	2,209	4	2,368	3,949
	%	7	93	0	100	0

Source: Continuous SHCS

3.2 Insulation measures

26. Installing or upgrading insulation is one of the easiest and most effective ways to improve the energy efficiency of a dwelling. It is estimated that in an uninsulated dwelling a third of all heat lost is through the walls and a quarter of heat is lost through the roof^[6].

27. In an amendment to the Housing (Scotland) Act in 2006, the tolerable standard was redefined to include a clause that dwellings must have satisfactory thermal insulation. This means that any dwelling with no loft insulation is classified as being Below Tolerable Standard (BTS) and by definition it is not reasonable to expect people to continue to live in a house that falls below this standard. Local authorities have a statutory duty and specific powers to deal with houses that fall below the tolerable standard. This applies to all dwellings in Scotland. More information on BTS is available in Chapter 5.

3.2.1 Loft insulation

28. Table 7 and Figure 3 show the levels of loft insulation in all dwellings. A dwelling is classified as 'not applicable' for loft insulation if it has a flat roof or another dwelling above it (i.e. a mid- or ground-floor flat).

29. Since 2003/04 the number of dwellings with no insulation has fallen and in 2011 represented just 32,000 dwellings, or 2% of those that could have loft insulation compared to 6% in 2003/04. The thickness of this insulation also increased so that 45% of dwellings with lofts had insulation depth of 200 mm or more in 2011, compared with 14% in 2003/04, with much of the increase occurring since 2007.

Table 7 Depth of loft insulation (000s), 2003/04 to 2011

Loft insulation	Survey Year
	2003/4	2004/5	2005/06	2007	2008	2009	2010	2011
none	110	96	104	99	101	96	46	32
1mm - 99mm	462	460	384	384	386	349	284	225
100mm - 199mm	953	982	987	987	818	872	806	745
200mm or more	258	289	315	315	471	485	628	812
Not applicable	486	472	524	524	555	542	593	554
All dwellings	2,269	2,301	2,315	2,309	2,331	2,344	2,357	2,368
Unweighted total	3,090	3,103	3,147	3,032	3,015	3,346	3,115	3,219

Source: Continuous SHCS

Figure 3 Depth of loft insulation (where applicable), 2003/04 - 2011

Source: Continuous SHCS

30. Table 8 shows in more detail the depth of loft insulation (where this measure is applicable) in 2010 and 2011. Dwellings in the social sector had a higher proportion of better insulated lofts than those in the private sector. 84% of private housing were insulated to 100 mm or more, and 42% of these exceeded 200 mm, whereas 94% of social dwellings had lofts insulated to 100 mm or more, and 57% of those had over 200 mm of loft insulation.

31. One of the reasons behind this is that the Scottish Housing Quality Standard (SHQS) requires at least 100 mm of loft insulation. All social rented dwellings must meet the SHQS by 2015 (see section 5.1 for more information).

32. Since 2010, loft insulation improved overall (see Table 8):

• The proportion of all housing with 100 mm or more increased 5 percentage points on 2010 levels.
• Private housing saw a similar improvement with a 4 percentage point increase since 2010, from 79% to 84%.
• Very good insulation beyond 300 mm improved a further 4 percentage points from 6% in 2010 to 10% in 2011.
• An estimated 14,000 fewer dwellings had no loft insulation at all.

Due to prior treatment of social housing, the majority of this improvement came from the private sector.

Table 8 Depth of loft insulation (000s and %) by tenure, 2011 and 2010

	Roof/loft insulation	Private Sector		Social Sector		All Tenures
		000s	%	000s	%	000s	%
2011	None	31	2	1	0	32	2
	1mm - 99mm	201	14	24	6	225	12
	100mm - 199mm	599	42	146	37	745	41
	200mm - 299mm	452	32	175	45	628	35
	300mm and more	137	10	47	12	184	10
	Total	1,420	100	394	100	1,814	100
2010	None	46	3	1	0	46	3
	1mm - 99mm	243	18	41	10	284	16
	100mm - 199mm	641	47	165	42	806	46
	200mm - 299mm	379	28	151	38	530	30
	300mm and more	64	5	34	9	98	6
	Total	1,373	100	392	100	1,764	100

Source: SHCS 2011 and 2010

3.2.2 Wall insulation

33. Most types of walls can be insulated in one way or another. In Scotland around three quarters of external walls are cavity walls and one quarter are solid or other walls. Other types include steel- frame dwellings and dwellings made from pre-fabricated concrete. These types, along with solid walls, may be classified as 'hard to treat' because low-cost cavity wall insulation (CWI) is not viable.

34. CWI installations are becoming increasingly difficult to identify as over time the injection holes age, fade or are covered up by later work. Contractors are also getting better at disguising their work. This may mean that we under estimate the number of homes which have had CWI installed.

35. CWI is not suitable for dwellings located in very exposed or wet areas. The survey is unable to collect this information, so it could be overestimating the number of cavity walls that are suitable for CWI.

36. Table 9 shows the number and percentage of external walls which are insulated as of 2011. Solid and other wall types are less likely to have insulation than cavity walls. Since 2007 the proportion of insulated cavity walls has increased from 53% to 66% in 2011. This compares to 9% of solid/other walled dwellings with insulation in 2007, rising to 11% in 2011.

Table 9 Exposed wall insulation by wall construction, 2007 to 2011^[7]

External Wall Construction	Insulation Added?	2007	2008	2009	2010	2011
Solid/Other (000s)	Not insulated	523	541	540	542	546
	Insulated	50	56	57	68	68
	Sub total	573	597	597	611	614
Cavity (000s)	Not insulated	816	766	732	671	600
	Insulated	924	967	1,015	1,076	1,154
	Sub total	1,740	1,733	1,747	1,747	1,754
All dwellings		2,313	2,330	2,344	2,357	2,368
Solid/Other (%)	Not insulated	91%	91%	90%	89%	89%
	Insulated	9%	9%	10%	11%	11%
	Sub total	100%	100%	100%	100%	100%
Cavity (%)	Not insulated	47%	44%	42%	38%	34%
	Insulated	53%	56%	58%	62%	66%
	Sub total	100%	100%	100%	100%	100%

Source: Continuous SHCS

37. Higher insulation levels have been required by building regulations since 1982 but, as shown in Table 10, action has been taken to improve pre-1983 dwellings by installing wall insulation. Energy efficiency is a criterion of the Scottish Housing Quality Standard, which applies to social housing (see section 5.1).

38. Social landlords have conducted significantly more work to improve dwellings overall. In the social sector, 44% of pre-1976 dwellings remain untreated compared with 69% in the private sector. The majority of work done has been to fill cavity walls (27% in the private sector and 36% in the social sector), which is generally the lowest cost improvement available.

39. The social sector has seen the greatest uptake of more expensive measures, where exposed walls are clad externally or internally with insulating material. As of 2011 nearly 20% (including those with both insulation types) of pre-1983 social sector housing had undergone such treatment compared with around 4% of private sector housing.

Table 10 Additional insulation in pre-1983 dwellings by Tenure

Insulation Added Post-Contruction	Private Sector		Social Sector		Total
	000s	%	000s	%	000s	%
None	906	69%	232	44%	1,138	62%
Cavity	359	27%	190	36%	548	30%
Internal or External Cladding	47	4%	96	18%	143	8%
Multiple types	5	0%	6	1%	10	1%
Total	1,316	100%	523	100%	1,840	100%
Sample Size	1,826		685		2,511

Source: SHCS 2011

3.3 National Home Energy Rating (NHER)

40. The SHCS uses NHER to rate dwellings on a scale of 0 (poor) to 10 (excellent) based on the total energy costs per square metre of floor area^[8]. Further information on NHER and SAP is provided in paragraphs 170 - 175. More detailed analysis and discussion can be found in the SHCS 2002 National Report^[9] and in Energy Efficiency and Estimated Emissions for the Scottish Housing Stock 2003/4^[10].

41. In 2011 it was not possible to determine NHER or SAP scores for 28 cases in the survey. These cases are excluded from any energy efficiency analysis.

42. Table 11 shows that in 2011 the most common energy rating of dwellings on the NHER scale is 8, the mean is 6.9 and the median 7. The proportion of dwellings rated with an NHER score of 8 or more was 46%, an increase of 6 percentage points on the corresponding figure from 2010.

Table 11 Dwellings by NHER scores (000s and %), mean and median values, 2010 and 2011

NHER score	2010			2011
	000s	%	Sample Size	000s	%	Sample Size
0	1	0	5	4	0	6
1	18	1	28	18	1	35
2	48	2	78	53	2	97
3	98	4	161	84	4	131
4	159	7	251	133	6	215
5	238	10	363	232	10	338
6	336	14	450	306	13	431
7	470	20	605	440	19	580
8	617	26	745	636	27	827
9	294	12	334	396	17	480
10	53	2	53	47	2	51
Sub-total	2,330	99	3,073	2,349	99	3,191
Unobtainable	27	1	42	19	1	28
Total	2,357	100	3,115	2,368	100	3,219
		95% Confidence Interval			95% CI
		lower	upper		lower	upper
Mean	6.71	6.64	6.78	6.86	6.79	6.93
Median	7			7

Source: SHCS 2010-11

43. Since 2010, 100,000 additional dwellings had achieved an NHER score of 9. The proportion of dwellings scoring 9 or 10 saw a 5 percentage point increase from 14 to 19 %.

Figure 4 The percentage of dwellings by NHER score, 2010 and 2011

Source: SHCS 2010/11

44. NHER scores may be banded such that a score of 7 or higher is considered 'good' and a rating of 2 or lower is 'poor'. Table 12 shows that, in 2011, 65% of dwellings were rated 'good' and 3% 'poor'.

Table 12 NHER band (000s and %)

NHER band	000s	%	Unweighted Sample size
Poor (0-2)	76	3	138
Moderate (3-6)	755	32	1,115
Good (7-10)	1,519	65	1,938
Unobtainable	19		28
Total	2,368	100	3,219

Source: SHCS 2011

45. Table 13 and Figure 5 show how the energy efficiency of the housing stock improved since 2003/4. In 2011 the mean and median NHER scores were 6.9 and 7, continuing the rising trend from 2003/4, when they were 5.8 and 6 respectively. In 2003/4, an estimated 40% of dwellings achieved a 'good' rating of 7 or above. By 2011 this proportion had risen to 65%.

46. Table 13 shows that the energy efficiency of social rented dwellings is better than that for the stock as a whole. However the proportion of both social and private stock achieving a 'good' rating increased by 20 or more percentage points since 2003/4. In 2011, 76% of social rented dwellings had a 'good' NHER rating, compared to 56% in 2003/4. Over the same period, the proportion of private sector dwellings rated 'good' rose from 35% to 61%.

Table 13 Banded NHER by Tenure, 2003/4-2011 (Row %)

Year	NHER Band (Row %)			Mean	Median	Sample size
	Poor	Moderate	Good
All Tenures
2003/4	6	54	40	5.8	6	3,088
2004/5	5	51	44	5.9	6	3,085
2005/6	4	48	47	6.1	6	3,146
2007	4	46	50	6.2	7	3,016
2008	3	48	49	6.3	6	3,006
2009	3	41	55	6.5	7	3,324
2010	3	36	62	6.7	7	3,073
2011	3	32	65	6.9	7	3,191
Private Sector
2003/4	8	58	35	5.5	6	2,220
2004/5	6	57	38	5.7	6	2,305
2005/6	5	55	40	5.8	6	2,340
2007	5	51	45	6.0	6	2,190
2008	4	53	43	6.0	6	2,227
2009	4	47	49	6.2	6	2,424
2010	4	39	57	6.5	7	2,261
2011	4	36	61	6.7	7	2,380
Social Sector
2003/4	2	43	56	6.5	7	868
2004/5	2	35	63	6.7	7	780
2005/6	1	32	67	6.9	7	806
2007	2	32	66	6.9	7	826
2008	1	32	67	7.0	7	779
2009	1	27	72	7.2	7	900
2010	1	27	73	7.3	8	812
2011	2	22	76	7.4	8	811

Source: Continuous SHCS

Figure 5 Dwellings by NHER bands. 2002-2011 (%)

Source: Continuous SHCS

47. Table 14 shows the NHER bandings alongside mean and median NHER scores by household characteristics.

48. Private-rented dwellings are over three times as likely to have a 'poor' NHER rating than owner-occupied dwellings. Ten percent of dwellings in the private rented sector are rated 'poor' compared to 3% of owner-occupied (Table 14).

Table 14 NHER band (Row %), mean and median values by household characteristics

	NHER Band (Row %)			Mean	Median	Sample size
	Poor	Moderate	Good
Owner-occupier	3	35	62	6.7	7	2,041
LA/other public	2	23	75	7.3	8	463
HA/co-op	2	22	76	7.6	8	348
Private-rented	10	38	52	6.3	7	339
Private Sector	4	36	61	6.7	7	2,380
Social Sector	2	22	76	7.4	8	811
Household Type
Single adult	6	28	66	7.0	8	445
Small adult	4	32	64	6.8	7	509
Single parent	2	25	73	7.2	8	151
Small family	2	28	70	7.0	8	443
Large family	4	40	56	6.6	7	217
Large adult	2	35	64	6.9	7	336
Older smaller	2	37	61	6.7	7	589
Single pensioner	4	31	65	6.9	7	501
< £100 p.w.	7	36	57	6.5	7	76
£100 -199.99	6	28	66	6.8	7	444
£200 -299.99	3	29	68	7.0	7	652
£300 -399.99	3	32	65	6.9	7	484
£400 -499.99	2	33	65	7.0	8	366
£500 -699.99	3	32	65	6.9	7	541
£700+	2	37	61	6.6	7	596
A	3	28	69	7.1	8	659
B	3	28	69	7.1	8	789
C	2	36	62	6.8	7	540
D	4	31	65	6.7	7	372
E	3	30	67	6.8	7	428
F	2	43	54	6.4	7	224
G	3	46	51	6.2	7	137
H	*	*	*	6.9	8	12
Unobtainable	11	64	25	5.3	5	30
All Scotland	3	32	65	6.9	7	3,191

Source: SHCS 2011

49. Around three-quarters of Local Authority and Housing Association achieve a 'good' NHER rating, compared with 62% of owner-occupied and 52% of private rented dwellings (Table 14).

50. Mean NHER ratings by tenure are also shown in Figure 6 for comparison. Housing association stock has the highest mean NHER score of 7.7, while private rented dwellings scores just 6.3 on average. The average NHER rating of single parent households is the highest of all household types at an NHER of 7.2 (Table 14).

51. The overall higher energy efficiency standard of social housing is likely attributable to the requirement for social landlords to meet the Scottish Housing Quality Standard by 2015, which includes an energy efficiency component (see section 5.1).

52. Single parent households are more likely than other household types to have a 'good' NHER rating, largely because they are also more likely to be in social housing.

53. Broadly, higher Council tax bands have lower NHER ratings - presumably because more expensive dwellings are generally larger and therefore less energy efficient (Table 14).

54. Table 15 shows NHER banding, mean and median scores by dwelling characteristics. Dwellings with a greater exposed surface area loose heat more quickly to the environment. As a result, detached and semi-detached houses generally have lower energy efficiency than terraced houses.

55. Flats, often shielded above and/or below by neighbouring dwellings, tend to have higher energy efficiency ratings still. Almost three quarters of tenements and other flats have 'good' energy ratings, whereas under a half of detached houses are rated 'good' (Table 15).

56. The mean NHER for detached houses is 5.9, compared to 7.4 for tenement and other flats. The median NHER scores are 6 and 8 respectively (Figure 6 and Table 15).

57. The newest dwellings are built to higher energy efficiency standards and tend to out-perform older buildings; 84% of dwellings built after 1982 have a 'good' energy efficiency rating compared to 40% of the pre-1919 occupied stock and around 65% of other age groups. Less than 1% of dwellings built after 1982 have 'poor' NHER ratings compared to 9% of those built before 1919 (Table 15). This trend is reflected in their mean NHER scores (Figure 6).

58. Less than 2% of the housing stock has no central heating. A further 4% have only partial central heating. Of those without central heating, around half (52%) have 'poor' NHER ratings, compared to just 2% of those with full central heating. Two thirds (67%) of those with full central heating have 'good' ratings. Over half (56%) of those with partial central heating have 'moderate' NHER scores and only 36% are rated 'good' (Table 15).

59. Seventy-one percent of dwellings in urban areas have a 'good' NHER rating compared with 32% of those in rural areas. Urban dwellings are also about five times less likely to be rated 'poor' than those in rural areas. The mean NHER score for dwellings in rural areas is 5.3 compared to 7.2 for those in urban areas. The median NHER scores are 5 and 8 respectively (Table 15).

60. Dwellings off the gas grid are seven times less likely to have a 'good' NHER rating and about eight times more likely to have a 'poor' NHER rating than those who are on the gas grid (see Table 15).

61. Rural dwellings are:

• more likely to be off the gas grid, and use less efficient fuels such as oil or solid fuels in their central heating
• more likely to be detached or semi-detached dwellings with a larger heat-loss surface area
• situated in areas with greater exposure to wind and colder temperatures.

The combination of these factors results in much lower energy efficiencies.

Table 15 NHER band (Row %), mean and median values by dwelling characteristics

	NHER Band (Row %)			Mean	Median	Sample size
	Poor	Moderate	Good
Type of Dwelling
Detached	7	45	49	5.9	6	792
Semi detached	2	40	58	6.6	7	689
Terraced	1	27	72	7.2	8	778
Tenement	4	23	74	7.4	8	552
Other flats	2	24	74	7.4	8	380
Age of Dwelling
Pre-1919	9	51	40	5.7	6	581
1919-1944	3	33	65	6.8	7	422
1945-1964	2	32	66	7.0	7	745
1965-1982	3	32	65	6.9	7	759
Post-1982	1	15	84	7.7	8	684
Extent of Central Heating
Full	2	31	67	7.0	7	3,032
Partial	8	56	36	5.6	6	113
No central heating	52	45	3	2.8	2	45
Primary Heating Fuel
Gas	1	24	75	7.4	8	2,337
Oil	8	85	7	4.6	5	279
Electric	14	51	35	5.3	5	486
Other fuel type	16	52	32	4.9	5	88
Urban/Rural
Urban	2	27	71	7.2	8	2,485
Rural	11	57	32	5.3	5	706
Gas Grid
Off Gas Grid	16	75	10	4.4	4	477
On Gas Grid	2	28	70	7.1	8	2,711
All Scotland	3	32	65	6.9	7	3,191

Source: SHCS 2011

Figure 6 Mean NHER by tenure, type of dwelling, age of dwelling and urban/rural indicator

Source: SHCS 2011

3.4 Standard Assessment Procedure (SAP)

62. The 2011 SHCS reports SAP 2005 only, SAP 2001 data will be available on request. SAP 2005 is for rating the energy efficiency of existing dwellings; it is scaled from 1 (poor) to 100 (excellent)^[11].

63. SAP 2005 takes space and water heating plus lighting into account. SAP 2001 did not include lighting. As with all versions of SAP, regional or climatic conditions are not taken account of in the calculations.

64. Table 16 shows the SAP 2005 rating of occupied housing stock for 2011. The largest proportion (39%) of dwellings are rated from 61 to 70, with the median score being 66 and the mean 62.6. In 2011, 26% of dwellings had a rating over 70; a small increase on 2010 figures when 27% had a rating over 70. As in previous years no sampled dwellings had a score of 91-100.

Table 16 Dwellings by banded SAP 2005 scores (000s and %)

Banded SAP 2005	000s	%	Unweighted Sample size
1-10	7	0	10
11-20	10	0	15
21-30	39	2	62
31-40	81	3	131
41-50	200	8	300
51-60	473	20	687
61-70	913	39	1,229
71-80	610	26	739
81-90	17	1	18
91-100	-	-	0
Sub-total	2,349	99	3,191
Unobtainable	19	1	28
Total	2,368	100	3,219
		95% CI
		lower	upper
Mean	62.6	62.1	63.0
Median	66

Source: SHCS 2011

65. SAP 2005 scores tend to follow the same pattern as NHER ratings when looking at dwelling and household characteristics.

66. Table 17 shows that flats have a higher mean SAP than houses, and post 1982 dwellings have a better SAP rating than all other dwelling age groups.

67. As with NHER, dwellings in the social sector have a better energy efficiency rating than those in the private sector.

68. Dwellings in rural areas have a mean SAP 2005 rating of 53.5 while for those in urban areas the mean is 64.3. The difference between urban and rural dwellings is more marked under the NHER (26% lower on average, compared with 17% lower under SAP). This is likely because NHER accounts for environmental factors such as local temperature, elevation and wind speed.

69. Dwellings on the gas grid have a higher mean SAP rating than those not on the gas grid. Under SAP 2005 the mean SAP for dwellings on the gas grid is 64.0 compared with 48.4 for those not on the gas grid.

Table 17 Mean and median SAP 2005 scores by dwelling and household characteristics

SAP 2005	95% Confidence Interval				Unweighted Sample size
	Mean	Lower bound	Upper bound	Median
Type of Dwelling
Detached	56.6	55.7	57.6	60.0	801
Semi detached	61.0	60.3	61.8	63.0	691
Terraced	65.4	64.7	66.0	67.0	781
Tenement	65.2	64.2	66.3	69.0	557
Other flats	65.3	64.2	66.4	67.0	389
Age of Dwelling
Pre-1919	54.6	53.5	55.8	57.0	590
1919-1944	62.1	60.9	63.3	65.0	422
1945-1964	63.8	63.1	64.6	66.0	747
1965-1982	63.1	62.3	64.0	66.0	768
Post-1982	68.0	67.3	68.6	69.0	692
Urban/Rural
Urban	64.3	63.9	64.8	67.0	2,498
Rural	53.5	52.5	54.6	56.0	721
Gas Grid
On Gas Grid	64.0	63.6	64.4	66.0	2,723
Off Gas Grid	48.4	47.2	49.6	50.0	493
Tenure
Owner-occupier	61.7	61.2	62.2	64.0	2,054
LA/other public	66.2	65.3	67.0	68.0	464
HA/co-op	67.0	66.0	68.1	69.0	355
Private-rented	58.2	56.4	60.0	62.0	346
Private Sector	61.2	60.7	61.7	64.0	2,400
Social Sector	66.5	65.9	67.2	68.0	819
All Scotland	62.6	62.1	63.0	66.0	3,219

Source: SHCS 2011

3.5 Approximated Energy Performance Certificate Energy Efficiency Ratings

70. Energy Performance Certificates (EPCs) were introduced for existing buildings from December 2008 to promote improvements to the energy efficiency of buildings. Every dwelling built, sold or re-let must now have an EPC. As part of this initiative, dwellings are given an energy efficiency rating (EER) on a scale from 'A' to 'G', with 'A' being the most and 'G' being the least energy efficient.

71. SHCS data allows the EER element of domestic EPCs to be approximated based on 'RDSAP' (Reduced Data Standard Assessment Procedure)^[12]. This section analyses approximated EER results. More information about EPCs can be found on the Scottish Government Building Standards website^[13].

72. Table 18 provides a breakdown of SHCS EERs by a number of dwelling and household characteristics. In 2011, 43% of dwellings in Scotland have an EER of 'D', while no dwelling rated 'A' was found within the SHCS sample. Nine percent of detached houses have an EER of 'F' compared with 4% or less for each of the other dwelling types. Over 80% of dwellings on the gas grid have an EER of band D or better, while less than 40% not on the gas grid achieve similar ratings. Likewise, dwellings in urban areas are more likely to have a higher EER than those in rural areas.

Table 18 Approximate EPC EERs by dwelling and household characteristics (%)

	B	C	D	E	F	G	Unob- tainable	Total	Sample size
Tenure
Private Sector	1	32	43	18	5	1	1	100	2,400
Social Sector	1	48	41	8	1	-	1	100	819
Type of Dwelling
Detached	-	19	45	25	9	1	1	100	801
Semi detached	-	25	54	18	3	1	0	100	691
Terraced	-	46	41	10	2	0	0	100	781
Tenement	3	47	34	11	4	0	1	100	557
Other flats	1	45	38	12	1	1	2	100	389
Age of Dwelling
Pre-1919	-	17	38	31	12	2	1	100	590
1919-1944	-	35	44	17	3	1	-	100	422
1945-1964	1	37	46	14	2	0	0	100	747
1965-1982	0	36	46	13	3	0	1	100	768
Post-1982	2	52	38	5	1	0	1	100	692
Gas Grid
On Gas Grid	1	39	43	13	3	0	0	100	2,723
Not on Gas Grid	-	3	34	40	16	4	4	100	493
Urban/Rural
Urban	1	40	44	12	2	0	0	100	2,498
Rural	-	15	37	30	13	2	3	100	721
All Scotland %	1	36	43	15	4	1	1	100	3,219
Households (000s)	17	853	1,007	363	92	17	19	2,368	3,219

Source: Continuous SHCS

3.6 CO₂ Emissions

73. This section presents modelled CO2 emissions in the Scottish housing stock. They are derived from the modelled energy required to maintain a standard heating regime (in line with modelled energy consumption used for fuel poverty estimates) and are calculated using SAP 2005 emissions factors (see Table 19).

74. These values are therefore based only on the energy performance of the building fabric, appliances, and fuel source. They do not include information about the number or behaviour of occupants and are not calibrated against emissions inventories.

75. The National Atmospheric Emissions Inventory (NAEI) is the official source of CO2 emissions data and their Greenhouse Gas Inventory^[14] is the source for checking statutory compliance with government targets.

Table 19 SAP 2005 Emissions Factors

SAP 2005 Emissions Factors (kgCO2/kWh)
Gas (mains)	0.194
Electricity	0.422
Oil	0.265
LPG	0.234
House coal	0.291
Wood logs	0.025

Source: BRE 2011^[15]

76. The SHCS estimates are used to compare emissions between years and different dwelling characteristics to show relative levels of carbon intensity.

Table 20 Average CO2 emissions by Dwelling Type (tonnes per year) and Total CO2 Emissions (Million tonnes per year), 2003/4 to 2011

Dwelling type	Survey Year
	2003/4	2004/5	2005/06	2007	2008	2009	2010	2011
Detached	11.2	12.0	11.1	11.3	11.1	11.0	8.5	8.4
Semi	7.2	7.4	7.3	7.4	7.3	7.0	5.8	5.7
Terrace	5.9	5.9	5.8	5.9	6.2	5.6	5.1	4.8
Tenement	4.5	4.3	4.2	4.4	4.2	4.2	4.0	3.9
Other flats	5.3	5.2	4.8	5.4	5.3	4.8	4.4	4.3
All dwellings	6.9	7.1	6.8	6.9	6.8	6.6	5.6	5.5
Total CO2 emissions	15.8	16.3	15.7	16.1	15.9	15.5	13.1	13.0

Source: Continuous SHCS

Figure 7 Average CO2 emissions by dwelling type (tonnes per year), 2003/4 to 2011

Source: Continuous SHCS

77. The time series of SHCS modelled CO2 emissions from domestic buildings between 2003/04 and 2011 is shown in ‎Table 20. As shown in Figure 7, since 2007 there has been a steady decrease in total modelled emissions.

78. Although a greater proportion of new dwellings are detached houses associated with higher emissions, ‎Table 21 and Figure 8 show that newer housing of all types has lower CO2 emissions than older stock.

Figure 8 Mean CO2 emissions by age and type of dwelling (Tonnes CO2 per year)

Source: SHCS 2011

Table 21 Mean CO2 Emissions by Age and Type of dwelling (tonnes per year)

Age of dwelling	Type of dwelling					Total
	Detached	Semi- detached	Terraced	Tenement	Other flats
Pre-1919	13.9	8.9	7.3	4.4	6.6	7.7
1919-1944	9.0	5.8	5.0	3.9	3.9	5.4
1945-1964	8.6	5.6	4.7	4.1	3.8	4.9
1965-1982	7.8	5.2	4.6	3.7	3.9	5.1
Post-1982	6.1	4.2	3.6	3.3	2.7	4.7
All dwellings	8.4	5.7	4.8	3.9	4.3	5.5

Source: SHCS 2011

79. As one of the lowest carbon intensity fuels under SAP 2005 (see Table 19), an inability to access the gas grid increases CO2 emissions. Gas heated dwellings are modelled to emit less than half the carbon of oil heated homes (Table 22).

80. In rural off-grid areas, high-emission fuels may be coupled with a greater degree of exposure leading to higher energy requirements and thus higher emissions.

81. There is not much difference between the CO2 emissions of using electricity or gas as a primary heating fuel and this gap will close as the grid is decarbonised.

Table 22 Mean and Median CO2 emissions (tonnes per year) by heating, fuel and location characteristics

Dwelling Characteristics	95% CI				Sample size
	Mean	lower	upper	Median
Extent of Central Heating
Full	5.5	5.4	5.6	4.5	3,032
Partial	6.2	5.5	6.9	5.2	113
No central heating	5.0	4.4	5.7	4.3	45
Primary Heating Fuel
Gas	5.0	4.9	5.1	4.3	2,337
Oil	11.0	10.2	11.8	8.7	279
Electric	5.9	5.6	6.2	5.0	486
Other fuel type	6.6	5.6	7.5	4.3	88
Urban/Rural
Urban	5.0	4.8	5.1	4.3	2,485
Rural	8.4	8.0	8.8	7.0	706
Gas Grid
On Gas Grid	5.1	5.0	5.2	4.4	2,711
Off Gas Grid	9.7	9.2	10.2	8.1	477
All Scotland	5.5	5.4	5.7	4.6	3,191

Source: SHCS 2011