SAP 10: A small change that hints at big things for decarbonising Britain’s heat

Kevin Stickney, managing director of Erda Energy, argues recent building assessment factor updates are an overdue (and incomplete) corrective, offering a glimpse of the UK’s electrified future for heating


he Standard Assessment Procedure (SAP) 10 attracted little fanfare

outside policy circles and the building and heating professionals when it was released back in July. Little wonder: it is a set of mainly dry assessment criteria for building design that aren’t even legally binding until reflected in updated building regulations, which probably won’t happen until 2019 or 2020. But these assessment criteria – last

adjusted in 2014 – have been a handbrake on the urgent need to decarbonise heat in the UK. As policy and fiscal stimulus have turbocharged the engine and investment in renewable electricity has laid out a smooth road, clean heat has been held back. With SAP 10 lifting the handbrake, this could be the start of a fundamental shift in how we decarbonise heat in this country. We should certainly hope so: heating

makes up 32% of our total emissions, far ahead of power (21%) and transport (24%).

SAP 10: LONG OVERDUE The SAP standards list a number of factors used in assessing the environmental performance of buildings. Though not yet legally binding, publishing them now gives the building sector forewarning on adjustments to factor into planning and design decision. So how have the standards changed?

The major talking point has been the carbon factor of grid electricity. Last updated in 2012 (though not effective until 2014), the current SAP figures stipulate 0.519 kgCO2/kWh. This means that for every kWh of grid electricity used by the building, it is estimated to produce just over half a kilogram of CO2. This compares to a carbon factor of 0.216kgCO2/kWh for mains gas, meaning designers have been more likely to opt for gas-powered heating in new buildings to meet emissions targets. However, in the six years since SAP

2012 was written, the UK’s grid has made great strides in decarbonisation. We’re used to reading headlines now about record renewable production and coal free days. To catch up, SAP 10 slashes


designers for years; artificially skewing environmental assessments. SAP 10 catches us up to today’s figures, but threatens to do the same again by 2020 if left static. Hopefully this won’t be the case. The

BEIS consultation response suggested it would look into updating the carbon factor based on a monthly method (though the target for new buildings wouldn’t change monthly) . If so, that’s a major design flaw solved.

the grid electricity carbon factor used to 0.233kgCO2/kWh, compared to 0.210kgCO2/kWh for gas. Suddenly, on paper, combined heat and

power systems and standard gas boilers look much less attractive compared to electric heating systems, such as geo- exchange and ground or air source heat pumps (GSHPs, ASHPs).

TIME TO ACCELERATE? This is a positive step. Once in use, the new figures will bring us much closer to reality. However, nothing is set in stone. Until the new standards are embedded in building regulations, anything can change. Bear in mind that, right now, electric heating such as geo-exchange is still assessed at 0.519kgCO2/kWh while 2017’s grid carbon intensity was estimated at 0.225kgCO2/kWh. However, there are some pretty hefty caveats. First, note that 2017’s grid carbon intensity is already below that used in SAP 10. Then consider that the new factors won’t apply until something like 2020. If grid decarbonisation continues – as current BEIS forecasts indicate – that could mean the carbon factor is significantly outdated by the time it comes into force. At the time of writing, you need to go back more than three years, to the 8th May 2015 at 10:15pm to find the last five minute period with an average grid power emission rate equal to or higher than 0.519kgCO2/kWh. In effect, this means SAP 2012 has been distorting the decisions of building

Figure 1: Energy efficient building

WHOLE SYSTEM THINKING If an updated and upgraded SAP goes some way towards unshackling electric heat sources, there are other trends pushing that way too. Since the Conservatives dropped the zero-carbon homes policy, organisations such as the Green Buildings Council have tirelessly campaigned for it to be reinstated. Now Labour have adopted the policy, increasing the pressure. This matters. Zero-carbon is more stringent than low carbon, and all but precludes solutions based on CHP or the gas network (barring some big leaps of faith about hydrogen).

Image 2:

Kevin Stickney, managing director of Erda Energy

Recent research from the Energy Systems Catapult and Oxford University also questioned the fairness of the current balance between standing and unit rates for electricity supply. Current arrangements, they argue, favour users of on-site generation such as solar, as by offsetting grid use they pay proportionally less towards transmission and distribution costs despite still relying on the network. Conversely, users of low-carbon electric heat systems pay more than their fair share due to higher electricity usage, despite also making environmentally responsible decisions. They advocate for a rebalancing to remove this distorting influence on heat.

Erda Energy T: 020 7236 0883


However, in effect it would only be to remove a longstanding artificial disparity, rather than offer particular support to low/zero-carbon heat.

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