Scottish Government

2 Energy Efficiency

16. Energy Efficiency is measured using two methodologies: the National Home Energy Rating ( NHER) and the Government's Standard Assessment Procedure for the Energy Rating of Dwellings ( SAP). The NHER is the most commonly used in Scotland as it allows for regional temperature variations whereas SAP uses the same standard for the whole of the UK. Both methods are reported on here.

17. 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 58, 59 and 60. More detailed analysis and discussion can be found in the SHCS 2002 National Report ⁴ and in Energy Efficiency and Estimated Emissions for the Scottish Housing Stock 2003/4 ⁵.

Table 5: NHER 2004/5

Figure 3: NHER 2004/5

Table 6: NHER Band 2004/5

18. Table 5 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 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 6 shows that 44% of dwellings in 2004/5 were rated "good", and only 5% "poor".

19. Table 7 and Figure 4 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 2004/5 this proportion had risen to an estimated 44%. Correspondingly fewer dwellings were given a poor rating in 2004/5 than in 2002. The calculation of 95% confidence intervals for these estimates, using Table 20, shows that these changes are statistically significant.

Figure 4: % Change in Energy Efficiency Ratings 2002 - 2004/5

Table 7: Change in Banded NHER by tenure 2002 - 2004/5

20. Table 7 shows that the improvements in the energy efficiency of social rented dwellings have been greater than those for the stock as a whole. In 2004/5, 63% 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 38%.

21. Table 8 shows the SAP rating of the occupied housing stock for 2004/5. The pattern is very similar to that for NHER, with the largest proportion of dwellings being rated between 61 and 70, and around 80% of dwellings rated between 41 and 80. The median SAP rating is 62.

Table 8: Banded SAP 2004/5

22. Figure 5 and Tables 9 to 11 show that properties in the social rented sector (covering local authority, other public sector organisations, housing associations and housing co-operatives) tend to have higher energy efficiency ratings than privately owned or rented properties.

23. Over 60% of social rented dwellings have a "good" NHER, compared to less than 40% of private sector housing. 14% of private rented dwellings are rated "poor", compared to the average of 5% across all sectors (Table 9).

24. 15% of pre-1919 dwellings have a "poor" NHER rating. Dwellings built after 1982 tend to be the most energy efficient with more than two thirds having a "good" NHER rating, making them three times as likely as pre-1919 dwellings to have to have a "good" rating.

25. 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 quarter of detached houses are rated "good" (Table 9). The mean NHER for detached houses is 4.9, compared to 6.6 for tenement flats (Figure 5). The lower energy efficiency of houses is related to the greater number of outside walls resulting in increased heat loss.

Figure 5: Mean NHER by tenure, type of dwelling and household income: 2004/5

26. Half of all dwellings without central heating have "poor" NHER ratings, compared to just 1% of those with full gas central heating. 54% of dwellings with full gas central heating are rated "good", compared to 30% with full electric central heating and just 1% of those with other types of central heating (oil or solid fuel) (Table 9).

27. Single parent households are more likely than other household types to have a "good" NHER rating, whereas large family and older smaller households are least likely to have a high energy efficiency rating but are most likely to have a "moderate" rating.

28. Households in the highest income band are least likely to have high energy efficiency ratings, with just over a quarter of such households achieving a "good" NHER (Table 9). This reflects the greater tendency for those on a higher income to live in detached houses which, as mentioned above, tend to have lower NHER ratings. The group with the next lowest average energy rating is those with the lowest incomes (Figure 5).

Table 9: NHER Band by tenure, age of dwelling, type of dwelling, fuel type and extent of central heating, type of household and household income (%)

Table 10: Mean and median NHER by tenure, age of dwelling, type of dwelling, fuel type and extent of central heating, type of household and household income

Table 11: Mean and median SAP by tenure, age of dwelling, type of dwelling, fuel type and extent of central heating, type of household and household income