The impact of SAP10 carbon emissions on low and zero carbon technologies for buildings
“Among other changes, SAP10 introduced a much lower carbon emission factor for electricity than the one currently used in Building Regulations; this is meant to reflect the grid electricity carbonisation. With the GLA (Greater London Authority) encouraging developers to use SAP10 from January 2019, it is expected that developments in London will now have the opportunity to test the impacts of the decarbonising grid on their design and servicing approach.”
The early adoption of the SAP10 carbon emission factors in the, newly published, GLA Energy Assessment Guidance has been the topic in the industry for the past few months. Spreadsheets are being reworked and carbon emission calculations are producing unexpected numbers!
But the reason this is such a hot topic goes beyond the mere calculations; this can have significant impacts on the selection of low and zero carbon technologies in buildings and can trigger a shift in the industry – as policy is meant to do. So let’s unpack it.
SAP10 was published in July 2018. The document noted that it is not currently to be used for any official purpose, and that SAP 2012 should continue to be used for Building Regulations. Its intention was to provide an indication of the expected future carbon emission factors that would inform, and potentially be adopted in, any future update to the Building Regulations.
A key implication from this update is that the proposed grid electricity emission factor is 0.233 kgCO2 per kWh. This is less than half the figure of 0.519 kgCO2 per kWh, currently used in Building Regulations, reflecting a rapid reduction in grid electricity emission factors since this was last updated.
The impact of this reduction is substantial on the reported carbon savings for technologies that gain their benefit from displacing grid electricity. For example, carbon savings from electricity generating technologies such as PV (photovoltaics) and district energy systems served by gas CHP (Combined Heat and Power), will be reduced. On the other hand, technologies such as heat pumps, that use electricity to generate heat, will see their carbon emissions decline.
The early adoption of SAP10 emission factors by the GLA intends to enable developers make appropriate, future-proofed, technology choices, accounting for the reduced grid electricity emission factors. For example, CHP will likely no longer be the technology that can deliver the highest emission savings in heat-led developments; and alternatives such as heat pumps and sources of secondary heat will need to be considered to help deliver the zero carbon target.
This shift is further supported by the policies set out in the draft New London Plan: the proposed ‘heat hierarchy’ lists the use of local secondary heat sources (in conjunction with heat pump, if required, and a lower temperature heating system) as the second option (after connection to an existing or planned heat network). Meanwhile, the implementation of CHP is moved further down in the hierarchy, and is supplemented by a note that attention should be paid to impacts on local air quality.
Finally, it is expected that the desire to reduce heating and hot water carbon emissions using the grid decarbonisation as a mechanism, will lead to increased electricity demands from the grid, at least in the short term and until demand side response measures realize their potential. Therefore, the possible impacts on the electricity infrastructure capacity required to serve the increased demand, should be further considered.
In the following months, developers, designers and energy consultants will be called to address these challenges; in addition to spreadsheet headaches, this will open up opportunities for innovative solutions that will be in the forefront of the global race in sustainable building design.