The zero-carbon tightrope

A tough job..

Throwing housebuilders, engineers, renewables specialists, NGOs, a government agency and several other experts together and asking them to agree on the future of ‘zero carbon’ was never going to be easy. But the UK Green Building Council wasn’t set up to duck the tough questions.

After 6 months of hard work, a huge amount of enthusiasm and more than a few late nights, the UK-GBC task group reported on the ‘Definition of Zero Carbon’ a couple of weeks ago. The background is fairly well rehearsed. A requirement to mitigate all of a home’s energy use through renewables, either on-site or connected by a private wire has left many in the industry pretty concerned.

In response, the UK-GBC brought together a group to assess the problem and suggest solutions. This had the blessing of the 2016 Zero Carbon Task Force and Government, and officials from several departments sat as observers at meetings.

Feedback so far

Since the launch of the report, at which we had about 80 guests cross-examining myself and the task group Chair, Mark Clare of Barratts, we’ve had plenty of feedback. Some have said we should have stuck to endorsing all on-site renewables. But a roughly equal number have said we should be allowing unlimited use of off-site. At the risk of sounding flippant, this probably means we’ve got it about right.

Building a consensus around a topic as charged as this necessitates compromise

The number of dissenters has actually been remarkably small, and we have received a lot of very positive feedback from people who see our recommendations as a pragmatic way forward, without undermining the spirit of the zero carbon policy. Building a consensus around a topic as charged as this necessitates compromise. Our group took into account a wide range of views and achieved a remarkable degree of consensus.

No cop out

But let me address some concerns for the sake of clarity. We believe zero carbon is the right policy. It has already brought about an unprecedented amount of innovation which simply wouldn’t have happened if we were still talking about ‘lower carbon’ and endless tweaks to Part L. So, for those who fear this is some sort of ‘cop-out’, I’ll reiterate - we believe that in many cases it is possible and desirable to achieve net zero carbon homes using on- and near-site renewable energy, and that in all cases we believe that the minimum threshold for on- or near-site carbon mitigation should be set at a high percentage of total energy used.

However, we need a definition that can be used for regulatory purposes, i.e. one that could be applied to 100% of homes (and in the future, other buildings too), including those facing constraints which prevent the use of on-site renewables, or which render them technically ineffective. Hence the need for a degree of flexibility.

An incentive

The approach we have recommended should encourage developers to opt for on- or near-site solutions wherever possible. The price of paying into the proposed Community Energy Fund must mean than developers will only do so if there is no alternative. That price could create a benchmark to incentivise the micro-renewables industry to offer developers a better, lower cost solution.

for those who fear this is some sort of ‘cop-out’, I’ll reiterate - we believe that in many cases it is possible and desirable to achieve net zero carbon homes using on- and near-site renewable energ

A major advantage of encouraging community-scale technologies is the possibility of providing local low or zero carbon heat that can be supplied to existing homes or other buildings such as schools. The Community Energy Fund could help to fund the necessary infrastructure to make such heat networks and other integrated energy solutions viable.

SAP differential

For those concerned about our assumptions, the only significant change from the RAB report model was regarding the so-called ‘SAP differential’. When applied, this factor means that energy generated on-site earns a significant carbon credit. So for example, in the case of an all-electric ‘zero carbon’ home, only 74% of its total electricity need be renewable, as it earns a significant carbon credit. The extent of this credit is questionable in carbon saving terms, and I believe it is currently under review. If we are to be honest about carbon savings, we need to take this into account. If the SAP differential was removed, the number of homes that failed to meet the current definition in the model rose from approximately 11% (in the RAB report) to around 80%.

Off-site not the answer

To those who think we should have opened the floodgates to allow unlimited use of off-site renewables, I say that it is essential that we optimize use of all the UK’s renewable energy resources. This includes harnessing the potential of the built environment to supply energy in ways that it may be much harder to retrofit later. The future is undoubtedly one of increased demand and competition for large-scale technologies, on or off-shore, with other sectors such as transport almost certainly prepared to pay a higher price for energy.

And yes, in future we should also be looking at counting embodied carbon too, which should be added to the total carbon footprint of our homes and buildings. But this was outside of our scope, which dealt only with the current regulatory regime.

You can’t please all of the people all of the time, but I’m confident that this is a robust piece of work, that will provide a clear steer to Government as it seeks to arrive at one consistent definition for zero carbon buildings over the coming months. There will be further challenges to come, but a major barrier will have been brought down and it will be up to the industry to get on and deliver.