carbon limited

From the zero carbon consultation, you can see that CLG has accepted that we need to resolve the onsite / offsite question. They have also moved away from the requirement for private wire networks or “direct connections” between generators and homes since it caused all sorts of problems.

So positive moves from CLG, but there is still a huge amount of confusion over what onsite and offsite actually mean. This is a crucial issue since only onsite energy will count towards carbon compliance, while offsite energy is only likely to count as an allowable solution.

It’s also likely that allowable solutions will include a whole range of possible measures, including offshore turbines, credit for S106 payments, and maybe even a buyout fund. Most low and zero carbon (LZC) technology will be unable to compete financially with measures like these and so simply wouldn’t get a look in.

There’s only so much carbon reduction you can cost effectively achieve through passive measures. So to give ourselves any chance of meeting ambitious carbon compliance levels, the definition of onsite must allow communal LZC systems.

It’s clear from the consultation doc that CLG don’t recognise how fundamental the problem is:

…LZC energy installations built within the development… would also count towards carbon compliance, and SAP provides for this. For the onsite electricity production to qualify, we would not stipulate any particular form of electrical connection between, or supply relationship between, the onsite generation and the homes on the development.

CLG has sidestepped the onsite / offsite issue here by claiming that SAP already resolves it, but SAP doesn’t! For example, under SAP you cannot use a communal wind turbine regardless of whether it’s directly connected to dwellings or not.

Further proof of SAP’s inability to rationally handle onsite energy arises when you try to use biomass CHP  (this one is a little esoteric but still very important – if you like, skip the next two paragraphs and just take it as read that SAP does not come anywhere near resolving the onsite / offsite issue). SAP assigns all the carbon benefit of CHP to the heat produced and assumes electricity from CHP is the same carbon intensity as the grid. While this is a pretty clumsy way to handle gas CHP, it’s becomes absurd for biomass CHP. This is because SAP doesn’t allow the carbon intensity of heat to drop below zero as this would incentivise designers to make buildings that save carbon by using more heat. As a result, a huge chunk of carbon savings simply disappears (unless you’re going for Code 6 in which case it counts but only towards unregulated emissions). God,what a muddle!

Let’s illustrate this with a concrete example. Let’s assume the CLG doesn’t listen to reason and requires unreasonably high levels of thermal efficiency. Developers therefore have to use MVHR and (in line with the Passiv Haus strategy) they strip out the wet heating in favour of a bit of electric heating built into the ventilation system. To achieve carbon compliance, the developer puts in biomass CHP to provide the scheme’s electricity from a low carbon source. But under SAP there’s no carbon benefit to the electricity produced! Some stays with the heat and some is lost to prevent the heat going carbon negative. Ah well, thinks the developer, I’ll get credit towards my carbon compliance by exporting zero carbon heat to surrounding building stock. Nope. Unfortunately the CLG is leaning towards counting exported electricity towards carbon compliance but perversely only counting exported heat towards allowable solutions.

Confused? I am. And you might be too because it’s an absolute mess. But enough of this negativity – here are the steps that would help sort this out. Feel free to plagiarise in your own response to the zero carbon consultation.

1. SAP must count all the carbon savings from communal LZC installations, including wind, biomass CHP, biomass heating, hydro, PV, etc
2. In the case of CHP, especially biomass CHP, carbon benefit needs to be split between heat and electricity to avoid perverse outcomes
3. There must not be a requirement for private wire connections between generators and homes. Communal LZC installations must be free to operate over licensed distribution networks
4. Assuming 1 and 3, a new definition of onsite is required. For example, onsite could mean anywhere within the redline of the development. Agreeing a definition might be tricky, but unless we find a workable definition there won’t be any affordable way of achieving even modest carbon compliance levels.
5. Exported heat should count towards carbon reductions in the same way as exported electricity