Scottish Government

3 Energy Efficiency

17. The overall energy efficiency of a household depends on the energy efficiency of the dwelling plus the behaviour of the occupants. The SHCS mainly concentrates on the energy efficiency of the dwelling but does ask respondents to what extent they monitor their energy use (see section 3.1).

18. The energy efficiency of a dwelling depends on the physical characteristics of that dwelling. 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.

19. 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.

20. In this chapter we report on both NHER and SAP (2005). We also report on analysis of presence and levels of insulation in Scottish dwellings, CO ₂ emissions from dwellings and results obtained by approximating the Energy Performance Certificates Energy Efficiency Ratings methodology using SHCS data.

3.1 Monitoring Energy Use

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

22. In 2010, about 33% of households say they monitor their energy use fairly closely and 12% say 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 just under 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 2010 (000s and %)

Figure 2 Extent to which energy use is monitored within property by net weekly household income band 2010 (%)

23. Although the extent to which householders monitor their energy use has not changed over the period 2008 to 2010, the number and proportion of people who have an energy-use monitoring device in their home has. Table 6 shows that the number of households with an energy-use monitoring device in their home has more than doubled over this period, although this still represents a very small proportion (4% in 2010) of all households in Scotland.

Table 6 Energy-use monitoring devices: 2008 to 2010 (000s and %)

3.2 Insulation measures

24. 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 .

25. 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 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.

2.2.1 Loft insulation

26. 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 a non heat loss roof. Since 2003/04 the number of dwellings with no insulation has more than halved and in 2010 represented just 3% of dwellings which can have loft insulation. In 2010, 628,000 dwellings had 200mm or more loft insulation, a significant increase since 2003/4 when just 258,000 had this depth.

Table 7 Depth of loft insulation (000s): 2003/04 to 2010

Figure 3 Depth of loft insulation (where applicable): 2003/04 - 2010

27. Table 8 shows in more detail the depth of loft insulation in 2010. The social sector have a higher proportion of better insulated lofts than the private sector. Less than 1% of social sector dwellings have no loft insulation, compared to 3% of private sector dwellings. One of the reasons behind this is that the Scottish Housing Quality Standard ( SHQS) includes the criteria that dwellings must have at least 100mm of loft insulation. All social rented dwellings must meet the SHQS by 2015 (see Chapter 5 for more information).

28. In 2010 more detailed information on the depth of loft insulation was collected. From Table 8 we can see that 6% of dwellings (with a loft) in Scotland have 300mm or more of loft insulation and just 46,000 (3%) dwellings have no loft insulation at all.

Table 8 Depth of loft insulation (000s and %) (2010)

2.2.2 Wall insulation

29. Most types of walls can be insulated in one way or another. In Scotland 74% of external walls are cavity walls and 24% are solid walls. Other types include steel- frame dwellings and dwellings made from pre-fabricated concrete, these types may be classified as 'hard to treat'.

30. Cavity wall insulation ( CWI) is becoming increasingly difficult to identify as over time the injection holes age, fade or are covered up by later work, and contractors are also getting better at disguising their work. This may mean that we under estimate the number of homes with CWI.

31. CWI is not suitable for dwellings located in exposed or wet areas. The survey is unable to collect this information, so could be overestimating the number of cavities which could be filled.

32. Table 9 shows the number and percentage of external walls which are insulated. 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 62% in 2010. This compares to 9% of solid/other walled dwellings with insulation in 2007, rising to 11% in 2010.

Table 9 External wall insulation by wall construction, 2007 to 2010

Note: All post 82 dwellings are assumed to have been insulated when built.

33. Table 10 looks in more detail at cavity wall insulation. In 2010, 46% of social dwellings had cavity wall insulation, compared to 29% of private sector dwellings.

34. Within the Energy Efficiency criteria of the SHQS there is an element which states cavity walls should be insulated where technically viable. Either cavity wall insulation or external or internal insulation is acceptable. There is a higher number and proportion of social sector cavity wall dwellings which have internal or external insulation compared to private sector dwellings. This is most likely due to the fact that dwellings in exposed sites cannot have cavity wall insulation.

Table 10 Cavity wall insulation by tenure (2010)

*All timber frame dwellings are included in the not technically viable category, as are post 82 dwellings as they are assumed to already have insulation.

3.3 National Home Energy Rating ( NHER)

35. The SHCS uses an enhanced level 0 NHER which rates dwellings on a scale of 0 (poor) to 10 (excellent) based on the total energy costs per square metre of floor area. Further information on NHER and SAP is provided in paragraphs 144 - 149. More detailed analysis and discussion can be found in the SHCS 2002 National Report ⁷ and in Energy Efficiency and Estimated Emissions for the Scottish Housing Stock 2003/4 ⁸ .

36. In 2010 it was not possible to determine NHER and SAP scores for 42 cases in the survey. These cases are excluded from any energy efficiency analysis.

37. Table 11 and Figure 4 show that the most common energy rating of dwellings on the NHER scale is 8 with a mean of 6.7 and a median of 7.1. 60% of dwellings were rated with an NHER score of 6 - 8.

Table 11 Dwellings by NHER scores (000s and Column %)

Figure 4 Number of dwellings by NHER score (000s)

38. Dwellings rated 7 or more are labelled as 'good' energy efficiency and those rated 2 or less are 'poor'. Table 12 shows that, in 2010, 62% of dwellings were rated 'good' and 3% 'poor'.

Table 12NHER band (000s and %)

39. Table 13 and Figure 5 show that the energy efficiency of the housing stock has improved. In 2010 the mean and median NHER scores were 6.7 and 7.1 respectively, statistically significant increases since 2009 when they were 6.5 and 6.8. In 2002 an estimated 31% of dwellings achieved a 'good' rating of 7 or above. By 2010 this proportion had risen to 62%. Correspondingly fewer dwellings were given a 'poor' rating in 2010 than in 2002.

Table 13 Banded NHER by Tenure 2002-2010 (Row %)

40. 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 have both increased by 30 percentage points since 2002. In 2010, 73% of social rented dwellings had a 'good' NHER rating, compared to 43% in 2002. Over the same period, the proportion of private sector dwellings rated 'good' rose from 27% to 57%.

Figure 5 Dwellings by NHER bands 2002-2010 (%)

41. The calculation of 95% confidence intervals for these estimates shows that the change in proportions in each NHER band between 2003/4 and 2010 is statistically significant. The change in the proportions rated 'moderate' and 'good' between 2009 and 2010 are also both statistically significant.

42. Within the private sector, private-rented dwellings are over twice as likely to have a 'poor' NHER rating than owner-occupied dwellings. 8% of dwellings in the private rented sector are rated 'poor' (Table 14).

43. Within the social sector, housing associations and housing co-operatives are more likely to have a 'good' NHER rating than local authority and other public sector organisations (Table 14).

44. Table 14 also shows that overall dwellings in the social rented sector (local authorities, other public sector organisations, housing associations and housing co-operatives) tend to have higher NHERs than privately owned or rented dwellings.

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

Table 14NHER band by household characteristics (Row %)

46. Table 15 shows NHER banding by dwelling characteristics. Houses have lower energy efficiency than other types of dwellings because more of their walls are exposed resulting in increased heat loss. Hence, terraced houses generally have higher energy efficiency ratings than detached houses.

47. Flats tend to have higher energy efficiency ratings than houses. The majority of tenements and other flats have 'good' energy ratings, whereas under a half of detached houses are rated 'good' (Table 15).

Table 15NHER band by dwelling characteristics (Row %)

48. Newer dwellings are more likely to have a 'good' energy efficiency rating than older dwellings; 85% of dwellings built after 1982 have a 'good' energy efficiency rating compared to 40% of the pre-1919 occupied stock. Less than 1% of dwellings built after 1982 have 'poor' NHER ratings compared to 8% of those built before 1919 (Table 15).

49. Only about 2% of the housing stock has no central heating. A further 3% have only partial central heating. Of those without central heating, just under half (39%) have 'poor' NHER ratings, compared to just 2% of those with full central heating. Over 60% of those with full central heating have 'good' ratings. Just over two thirds of those with partial central heating have 'moderate' NHER scores and almost 30% are rated 'good' (Table 15).

50. Those who use gas as their primary heating source are over twice as likely as those who use electricity, and more than 8 times as likely than those who use oil to have a 'good' NHER rating. 12% of those who use 'other fuel types' ⁹ have a 'poor' NHER score compared with only 1% of those who use gas and 9% of those who use electricity and 13% of those who use oil (Table 15).

51. 68% of dwellings in urban areas have a 'good' NHER rating compared with 29% of those in rural areas. Urban dwellings are also about eleven times less likely to be rated 'poor' than those in rural areas.

52. Dwellings off the gas grid are 7 times less likely to have a 'good' NHER rating and about 18 times more likely to have a 'poor' NHER rating than those who are on the gas grid. Rural dwellings are more likely to be off the gas grid, and use oil or solid fuels in their central heating than those in urban areas.

53. Mean NHER scores show the relative average energy efficiency of housing. Figure 6 shows mean NHER scores by tenure, dwelling type, household income and urban/rural location. Table 16 and Table 17 show NHER means and medians by household characteristics and dwelling characteristics respectively.

54. Housing association stock has a mean NHER of 7.7 compared to private rented sector stock of 6.3. The average NHER rating of single parents is the highest of all household types at an NHER of 7.2 (Table 16).

55. Broadly, the higher the income band and the higher the Council tax band, the lower the NHER rating - presumably both correlating with larger, less energy efficient dwellings (Table 16).

56. The mean NHER for detached houses is 5.7, compared to 7.4 for tenement flats. The median NHER scores are 6.2 and 7.9 respectively (Figure 6 and Table 17).

57. Dwellings in urban areas tend to be more energy efficient than those in rural areas. The mean NHER score for dwellings in rural areas is 5.1 compared to 7.0 for those in urban areas. The median NHER scores are 4.9 and 7.4 respectively (Table 17).

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

Table 16 Mean and median NHER score by household characteristics

Figure 7 Mean and median NHER score by dwelling characteristics

Table 17 Mean and median NHER scores by dwelling characteristics

3.4 Standard Assessment Procedure ( SAP)

58. The 2010 SHCS reports SAP 2005 only, SAP 2001 data will be available on request. SAP 2005 is the most up-to-date SAP system for rating the energy efficiency of existing dwellings, it is scaled from 1 (poor) to 100 (excellent) .

59. 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.

60. Table 18 shows the SAP 2005 ¹⁰ rating of occupied housing stock for 2010. The largest proportion of dwellings is rated from 61 to 70, with the median score being 64 and the mean 61.9. In 2010, 23% of dwellings had a rating over 70, this was a significant increase on 2009 figures when just 15% had a rating over 70. As in previous years no dwellings have a score of 91-100.

Table 18 Dwellings by banded ' SAP 2005' (000s and %)

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

62. Table 19 shows the mean SAP 2005 ratings by dwelling and household characteristics .They show that, flats have a higher mean SAP than houses, and post 1982 dwellings have a better SAP rating than all other dwelling age groups.

63. As with NHER, dwellings in the social sector have a better energy efficiency rating than those in the private sector. Dwellings in rural areas have a mean SAP 2005 rating of 52.3 while for those in urban areas the mean is 63.8.

Table 19 Mean and median ' SAP 2005' scores by dwelling and household characteristics

64. 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 63.2 compared with 46.5 for those not on the gas grid.

3.5 Approximated Energy Efficiency Ratings

65. Energy Performance Certificates ( EPCs) were introduced 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' the least energy efficient.

66. SHCS data allows the EER element of domestic EPCs to be approximated based largely on the same dwelling data as the official EPCEERs but using SAP rather than RDSAP methodology ¹¹ . This section analyses the approximated EER results. More information about EPCs can be found on the Scottish Building Standards Division web site ¹² .

67. Table 20 provides a breakdown of SHCSEERs by a number of dwelling and household characteristics. In 2010, 44% of dwellings in Scotland have an EER of 'D', while no dwelling rated 'A' was found within the SHCS sample. 9% of detached houses have an EER of 'F' compared with 3% or less for other dwelling types. 80% of dwellings on the gas grid have an EER of band D or better, while only 27% of those dwellings not on the gas grid are band D or better. Likewise, dwellings in urban areas are more likely to have a higher EER than those in rural areas.

Table 20 Approximate EPCEERs by dwelling and household characteristics (%)

3.6 CO ₂ Emissions

68. From SHCS outputs, estimates are made of gaseous emissions - sulphur (SO _x), nitrous oxides (NO _x) and carbon dioxide (CO ₂) emitted as a result of the total energy requirement from all fuels including electricity (see section 6.12). This section presents results for CO ₂ emissions. Results for the other gases are available.

69. The time series of CO ₂ emissions from domestic dwellings from 2003/04 to 2010 is shown in Table 21. There has been a reduction in both mean CO ₂ emissions per dwelling and total emissions from the housing stock over the period. Since 2007 there has been a steady decrease in total emissions, with a significant drop between 2009 and 2010.

70. Noticeably, detached houses have the highest CO ₂ emissions and tenements have the lowest emissions. Between 2009 and 2010 total and average emissions fell significantly due to a significant improvement in the energy efficiency of dwellings (See Section 3.3).

71.

Table 21 Average CO ₂ emissions (tonnes per year) by Dwelling Type and Total CO ₂ Emissions (Million tonnes per year) 2003/4 to 2010

Figure 8 Average CO ₂ emissions (tonnes per year) 2003/4 to 2010 by dwelling type

72. Although a greater proportion of new housing is detached housing and that type of housing has the highest emissions, Table 22 and Figure 8 shows that newer housing of all types is more energy efficient than older stock.

Table 22 Mean CO ₂ Emissions by Age and Type of dwelling 2010 (Tonnes CO ₂ per year)

Figure 9 Mean CO ₂ Emissions by Age and Type of dwelling 2010 (Tonnes CO ₂ per year)

73. Table 23 contains more details for 2010. Although detached dwellings emit the highest CO ₂ emissions, the age of a dwelling is also an important factor - the older the dwelling the higher the CO ₂ emissions. Use of gas for heating at least halves emissions compared to oil so naturally being off gas grid or in a rural location also increases CO ₂ emissions. There is not much difference between the CO ₂ emissions of using electricity or gas as a primary heating fuel.

Table 23 Mean and Median CO2 emissions (tonnes per year) by dwelling characteristics (2010)