| INTENSITY ANALYSIS this year. In light of this, the Greater London Authoritys decision to allow new development applications from January 2019 to use the annual average carbon values is surprising and, perhaps, somewhat premature. Approved Document L may undergo future revision, so its also worth considering the EU Energy Performance of Buildings Directive (EPBD). This requires the energy performance of a building to be expressed by a numeric indicator of primary energy use in kWh/(m2.y) for both energy performance certification and compliance with minimum energy performance requirements. In other words, the building compliance metric is expected to shift from carbon emissions to primary energy use. While this alters the outcomes on a technology basis slightly, the argument of seasonal variation in grid intensity still applies. The proposed grid primary energy factor (PEF) in SAP10 is 1.738, down from the 3.07 figure used today and, again, it appears slightly optimistic. Interestingly, there has been a prolonged debate between the EU Commission and EU Council about the appropriate PEF to apply across other directives, such as the Energy Efficiency Directive and EcoDesign. The figure in the pipeline is a reduction from 2.5 to perhaps 2.1. Can we seriously suggest that the UK generation mix during the life-cycle of SAP 10 will be significantly cleaner than other member states? Until the inter-seasonal storage of low carbon electricity generation is a reality, its imperative the changing Carbon intensity analysis 400 350 gCO2/kWh VOICES 300 250 200 Heating season & predominant CHP generation period Heating season & predominant CHP generation period 150 Jan Feb Mar Apr May Jun 201518 average electric intensity Jul Aug Sep Oct Nov Dec BRE proposed SAP 10 electrical factor Figure 2: Seasonal carbon intensity analysis Source: internal analysis and electricityinfo.org/fuel-mix-archive/#data generation mix throughout the year is reflected in national calculation models that avoid misrepresentation of actual energy and emissions use. Indeed, deeper granularity may be necessary for future smart-grid applications and timeof-use tariffs down, perhaps, to half-hourly values. Robust, validated data is available to support monthly values, so SAP 10 could be amended to a more realistic and representative model. R600 EVOLUTION Condensing ultra low nox premix commercial boiler Probably Europes most efficient fully condensing fully modulating pre-mix gas-fired commercial boiler. Exceptional high quality Highest system flexibility Easy servicing Environmentally friendly Detailed specifications and performance data available THE CONSULTANTS & CONTRACTORS CHOICE. For further information or to receive a technical guide tel: 0208 783 3050 or email: info@stokvisboilers.com www.stokvisboilers.com 54 February 2019 www.cibsejournal.com CIBSE Feb19 pp53-54 Remeha.indd 54 25/01/2019 16:03