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2 Energy Efficiency

20. 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 variations. The SAP only considers energy used by heating and hot water and ignores any regional or geographical variation. Both methods are reported on here.

21. 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. SAP ratings run from 1 to 100. Further information on NHER and SAP is provided in paragraphs 87 - 89. More detailed analysis and discussion can be found in the SHCS 2002 National Report ⁶ and in Energy Efficiency and Estimated Emissions for the Scottish Housing Stock 2003/4 ⁷.

22. In 2005/6 it was not possible to determine NHER and SAP scores for 1 case in the survey. This case is excluded from any energy efficiency analysis.

23. Table 11 and Figure 4 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 6. Over 80% of dwellings were rated between 4 and 8. Dwellings rated 7 or above are considered to have "good" energy efficiency. Those rated 2 or below are considered "poor". Table 12 shows that 47% of dwellings in 2005/6 were rated "good" and only 4% "poor".

Table 11: Dwellings by NHER scores 2005/6 (000s and %)

Figure 4: Number of dwellings by NHER score 2005/6 (000s)

Table 12: NHER band 2005/6 (000s and %)

24. Table 13 and Figure 5 show how 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 2005/6 this proportion had risen to an estimated 47%. Correspondingly fewer dwellings were given a poor rating in 2005/6 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 2005/6 is statistically significant. The changes in the proportions rated 'good' and 'moderate' between 2003/4 and 2005/6 are also statistically significant.

Figure 5: Dwellings by NHER bands 2002-2005/6 (%)

Table 13: Change in banded NHER by tenure 2002-2005/6 ( %)

25. Table 13 shows that improvements in energy efficiency of social rented dwellings have been greater than those for the stock as a whole. In 2005/6, about two thirds 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 40%.

26. Table 14 shows the SAP rating of occupied housing stock for 2005/6. The pattern is very similar to that for NHER, with the largest proportion of dwellings rated between 61 and 70, and just under 80% of dwellings rated between 41 and 80. The median SAP rating is 63.

Table 14: Dwellings by banded SAP 2005/6 (000s and %)

27. Figure 6 and Table 15- Table 17 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. 14% of dwellings in the private rented sector are rated "poor", compared to an average of 4% across all sectors ( Table 15).

28. Flats tend to have higher energy efficiency ratings than houses. The majority of tenements and other flats have "good" energy ratings, whereas less than a third of detached and semi-detached houses are rated "good" ( Table 15). The mean NHER for detached houses is 5.1, compared to 7.0 for tenement flats ( Figure 6). The median NHER scores are 5 and 7 respectively ( Table 16). Houses have a 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.

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

29. Newer dwellings are more likely to have a good energy efficiency rating than older dwellings, three quarters of dwellings built after 1982 have a good energy efficiency rating compared to just under a quarter 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.

30. 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, 60% have "poor" NHER ratings, compared to just 2% of those with full central heating - with almost half 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 15).

31. Those who use gas as their primary heating source are more than twice as likely as those who use electricity and around nine times more likely than those who use oil to have a 'good' NHER rating. Those who use 'other fuel types' ⁸ such as solid fuels are over 30 times more likely than those who use gas to have a 'poor' NHER score.

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

33. There does not appear to be a straightforward relationship between income and energy efficiency rating.

34. Dwellings in urban areas have higher NHER ratings than those in rural areas ( Figure 6). Urban dwellings are around twice as likely to have a good NHER rating and 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 6. 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 15: NHER band by dwelling and household characteristics (%)

Table 16: Mean and median NHER score by dwelling and household characteristics

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

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