Energy Efficiency Standard for Social Housing: peer review

Appendix D - Pre- & Post-2002 Specs

Example Group H Performance Parameters

The period of construction describing example group H bridges two RdSAP age bands; I (1999-2002), and J (2003-2007). The reason for this split in the RdSAP age bands is due to changes in the buildings standards, most significantly the 6 ^th amendment which came into force from 4 ^th March 2002. This saw not only the application of more onerous U-values for external constructions, but a difference in the values relative to the fuel type and efficiency of the system. As a result, many of the default RdSAP assumptions demonstrate very different performance parameters.

The tables below summarise the performance parameters associated with the default RdSAP assumptions, example dwelling specifications, minimum Building Standards in place at the beginning of the example group H construction period, and the changes which came into force halfway through.

Walls - Table 1 summarises the wall U-values determined by the default RdSAP assumptions for a number of Scottish construction types, as well as the original and updated U-value criteria applicable to new constructions. The wall U-values are in compliance with the Building Standards corresponding to the earlier time period, relative to age band I. The latter half of the construction period, relative to RdSAP age band J, are subject to more onerous U-values.

Table 1 Example group H wall U-values

Floor - Table 2 summarises the floor U-values determined by the default RdSAP assumptions and calculation methodology. It can be seen that the floor U-values for example dwellings 22 and 23, are in compliance for the earlier period of the timeframe corresponding to age band I.

Table 2 Example group H floor U-values

Roof - Table 3 shows the U-values for the various criteria assuming a pitched roof with insulation between joists. The specification for the example dwelling roof insulation is 200mm. Based on this assumption, new dwellings completed between 1999 to the beginning of 2002 would meet compliance, however as of the 6 ^th amendment to the Building Standards an increase in the loft insulation thickness would be necessary.

Table 3 Example group H roof U-values

Windows - Table 4 details the RdSAP window U-value assumptions and the minimum building standards applicable to the construction period from 1999 to 2007. The specification for example group H baseline glazing is 'post-2003', however the RdSAP data for glazing installed before 2003 is also provided for reference.

It can be seen that specification of 'post-2003' standards ensures that the majority of the example dwellings meet compliance with the more recent buildings standards, however the properties featuring electric heating require an even lower U-value, of 1.8 W/m ².K. It would be expected that properties constructed in the earlier half of the example group H timeframe, up to 2002, would have a poorer U-value than the assumed 2.0 W/m ².K.

Table 4 Example group H window U-values