- 55% CO2 emission factor reduction for Electric
Electricity’s annual average CO2 emission factor will be reduced from 0.519 kgCO2/kWh to 0.233 kgCO2/kWh (a 55% reduction) and will place electricity just behind gas which has a CO2 emission factor of 0.210 kgCO2/kWh.
Targets within SAP 2012 are currently based on mains gas, so this heavily penalises electric use, and certainly any new builds with all electric heating are incredibly difficult to pass without additional renewable technologies being installed. However, under SAP 10 achieving compliance with electric heating will become much easier and we anticipate a shift from gas to electric heating in homes. This reflects the decarbonisation of the National Grid.
- Heat loss assumption for District Heating Networks (DHN) will increase to 50%
Developments with DHN could notice a big drop in SAP performance. Currently, default heat losses from the pipework of DHNs are assumed to be 5-20% in SAP. Going forward, a new development with no evidence of heat losses will have to assume 50%.
- Change to heating pattern
Currently SAP uses a standard heating pattern which assumes that homes are heated differently on weekdays and weekends. SAP 10 has been changed to apply a consistent daily pattern for all days of the week. This will have the effect of reducing energy use and costs across the board.
- Overheating risk will increase
The assessment of overheating contained in Appendix P has been changed to more accurately assess the potential for leaving windows open during hot weather. In SAP 10, if natural ventilation is used, assessors will be required to indicate if there is a source of noise that prevents windows being left open, and also if there is a security risk where windows are left open at night. We’d recommend a thermal modelling assessment for a more in-depth analysis where overheating risks are anticipated.
- Thermal bridging
The default y-value used in assessments where no details of thermal bridging are provided has been raised from 0.15 w/m2k to 0.2 w/m2k in SAP 10. This will create an even more severe penalty for developers who do not consider heat loss through building junctions.
- Bath and shower flow rates will be considered
Hot water consumption has until now been based on a standardised usage. Flow rates will now need be entered into SAP 10 so we will start to see a certain amount of variation between shower fittings being used.
Water efficiency calculations are already required under Part G of the building regs, so there will now be some informed cross over between these two assessments.
- Excess electricity from PV panels can be stored
SAP 2012 used a fixed assumption for the proportion of electrical energy generated by Photovoltaic (PV) systems and consumed within the dwelling. This was attributed regardless of whether there was a direct connection to a dwelling, or whether, as is often the case on blocks of flats, only one exists to a landlords supply.
This has been replaced by a formula which will only factor in a PV supply to those flats directly connected. This will impact on those developments which are relying on a carbon reduction for a planning condition, and much more consideration will need to be taken made when designing and installing systems.
There is now also recognition of the presence of battery storage in the assessment.
- Updates to reflect changes in lighting technology
SAP 10 will calculate a ‘reference lighting capacity’ based on the dwellings floor area and solar gains. Should this capacity not be reached, or be exceeded, the predicted lighting energy will be increased as a result.
- Thermal mass parameter
Indicative options of low, medium and high for thermal mass parameter have been removed from SAP 10. Therefore, all dwellings will now be required to have a calculated thermal mass parameter based on their individual element areas and kappa values.