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2 Energy Efficiency

22. 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). The NHER is the most commonly used in Scotland as it considers all energy use and allows for regional and geographical climatic variations. The SAP only considers energy used by heating and hot water (and lighting under SAP 2005), and ignores any regional or geographical variation. Both methods are reported on here.

23. 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 106-116. More detailed analysis and discussion can be found in the SHCS 2002 National Report ¹⁰ and in Energy Efficiency and Estimated Emissions for the Scottish Housing Stock 2003/4 ¹¹.

Table 7: Emulated EPC by dwelling and household characteristics (Row %)

24. The 2007 SHCS reports SAP using SAP 2001 and SAP 2005. SAP 2005 is the most up to date system for rating the energy efficiency of dwellings. It is scaled from 1 (poor) to 100 (excellent) whereas SAP 2001 has a maximum rating of 120.

25. In 2007 it was not possible to determine NHER and SAP scores for 17 cases in the survey. These cases are excluded from any energy efficiency analysis.

26. Table 8 and Figure 3 show that the most common energy rating of dwellings on the NHER scale is 7. The median, at or above which 50% of dwellings are rated, is 7. Around 80% of dwellings were rated between 4 and 8. Dwellings rated 7 or more are labelled as 'good' energy efficiency. Those rated 2 or less are 'poor'.

Table 8: Dwellings by NHER scores 2007 (000s and Column %)

Figure 3: Number of dwellings by NHER score 2007 (000s)

27. Table 9 shows that, in 2007, 50% of dwellings were rated 'good' and 4% 'poor'.

Table 9: NHER band 2007 (000s and %)

28. Table 10 and Figure 4 show that the energy efficiency of the housing stock has improved. In 2002 an estimated 31% of dwellings achieved a 'good' rating of 7 or above. By 2007 this proportion had risen to about 50%. Correspondingly fewer dwellings were given a 'poor' rating in 2007 than in 2002. The calculation of 95% confidence intervals for these estimates shows that the change in proportions in each NHER band between 2002 and 2007 is statistically significant. The changes in the proportions rated 'good' and 'moderate' between 2004/5 and 2007 are also statistically significant.

Figure 4: Dwellings by NHER bands 2002-2007 (%)

Table 10: Banded NHER by Tenure - 2002-2005/6 (Row %)

29. Table 10 shows that improvements in energy efficiency of social rented dwellings have been greater than those for the stock as a whole. In 2007, 66% 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' increased from 27% to 45%.

30. Table 11 shows the SAP 2001 rating of occupied housing stock for 2007. The pattern is very similar to that for NHER, with the largest proportion of dwellings rated between 61 and 70, with just below 80% of dwellings rated between 41 and 80. The median SAP rating is 64.

31. Table 12 shows the SAP rating of occupied housing stock for 2007 calculated using SAP 2005 ¹². Again, the largest proportion of dwellings is rated between 61 and 70. However, using SAP 2001, around a third of dwellings have an energy rating over 71 while, using SAP 2005, only 10% of dwellings have a rating over 71, with no dwellings with a score of 91-100.

Table 11: Dwellings by banded SAP 2001, 2007 (000s and %)

32. Table 12 shows the SAP rating of occupied housing stock for 2007 calculated using SAP 2005 ¹³. Again, the largest proportion of dwellings is rated between 61 and 70. However, using SAP 2001, around a third of dwellings have an energy rating over 71 while, using SAP 2005, only 10% of dwellings have a rating over 71, with no dwellings with a score of 91-100.

33. Flats tend to have higher energy efficiency ratings than houses. The majority of tenements and other flats have 'good' energy ratings, whereas around a third of detached and semi-detached houses are rated 'good' (Table 13). The mean NHER for detached houses is 5.2, compared to 7.0 for tenement flats. The median NHER scores are 5 and 7 respectively (Table 15).

34. Houses have lower energy efficiency because they have more outside walls resulting in increased heat loss. Hence terraced houses generally have higher energy efficiency ratings than detached houses.

Table 12: Dwellings by banded SAP 2005, 2007 (000s and %)

35. Newer dwellings are more likely to have a 'good' energy efficiency rating than older dwellings; 76% of dwellings built after 1982 have a 'good' energy efficiency rating compared to fewer than 25% of the pre-1919 occupied stock. Less than 1% of dwellings built after 1982 have 'poor' NHER ratings compared to more than 1 in 10 of those built before 1919.

36. Only about 3% of the housing stock has no central heating. A further 4% have only partial central heating. Of those 3% without central heating, 47% have 'poor' NHER ratings, compared to just 2% of those with full central heating. Over 50% of those with full central heating having 'good' ratings. More than half of those with partial central heating have 'moderate' NHER scores with just over a third rated 'good' (Table 13).

37. Those who use gas as their primary heating source are around twice as likely as those who use electricity and around 20 times more likely than those who use oil to have a 'good' NHER rating. Those who use 'other fuel types' ¹⁴ such as solid fuels are over 20 times more likely than those who use gas to have a 'poor' NHER score.

Figure 5: Mean NHER by tenure, type of dwelling, household income and urban/rural indicator

38. Figure 5 and Table 14 show that dwellings in the social rented sector (local authorities, other public sector organisations, housing associations and housing co-operatives) tend to have higher energy efficiency ratings than privately owned or rented dwellings. 17% of dwellings in the private rented sector are rated 'poor', compared to an average of 4% across all sectors (Table 14).

39. Single parent households are more likely than other household types to have a 'good' NHER rating.

40. There does not appear to be a straightforward relationship between income and energy efficiency rating. With Council Tax, generally the lower the band, the higher the % of dwellings which have 'good' NHER ratings. 59% of dwellings with Council Tax band A compared with 32% of those with band G are rated 'good'. Council Tax band H does not follow this trend but the sample size is very small.

41. 56% of dwellings in urban areas have a 'good' NHER rating compared with 21% of those in rural areas (Table 13).

42. As noted above, newer dwellings are more likely to have a 'good' energy efficiency rating than older dwellings; 76% of dwellings built after 1982 have a 'good' energy efficiency rating compared to fewer than 25% of the pre-1919 occupied stock. Less than 1% of dwellings built after 1982 have 'poor' NHER ratings compared to more than 1 in 10 of those built before 1919 (Table 13).

43. Only about 3% of the housing stock has no central heating. A further 4% have only partial central heating. Of those 3% without central heating, 47% have 'poor' NHER ratings, compared to just 2% of those with full central heating. Over 50% of those with full central heating having 'good' ratings. More than half of those with partial central heating have 'moderate' NHER scores with just over a third rated 'good' (Table 13).

44. Urban dwellings are more than twice as likely to have a 'good' NHER rating and are also around six times less likely to be rated 'poor' than those in rural areas. The median NHER rating of rural dwellings is 5, compared to 7 for urban areas and a national median of 7.

45. Dwellings off the gas grid are almost 5 times less likely to have a 'good' NHER rating and around 8 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.

Table 13: NHER band by dwelling characteristics (Row %)

Table 14: NHER band by household characteristics (Row %)

Table 15: Mean and median NHER score by dwelling characteristics

Table 16: Mean and median NHER score by household characteristics

Table 17: Mean and median SAP 2001 score by dwelling and household characteristics

Table 18: Mean and median SAP 2005 score by dwelling and household characteristics

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