Last week the Department for Communities for Local Government went some way to answering this, by opening a public consultation on that very topic. You can have your say until October 15th. Details here.
There are several recommendations listed in this document – here’s some of the key points.
It’s suggested the definition of a ‘Zero Carbon Home’ has changed. In effect we would be moving the goalposts to our benefit… Currently, to be classed as truly zero carbon, a house needs to generate enough power on site to cover all energy use. That includes heating, lighting, hot water, TV’s, fridges, cookers, chargers, lawnmowers… the list goes on.
The consultation suggests that only ‘regulated’ energy use is included in the target (which is heating, hot water, ventilation and lighting only), and the electricity generated to fuel these will not necessarily need to be made on site.
Why the change of approach? The document reads: “It was originally intended that new homes would meet the whole of the zero carbon standard ‘on-site’. However, the government recognises that it would not be cost effective at this time, affordable or technically feasible to meet the zero carbon homes standard in all cases.”
The consultation suggests a three tier approach to house building from 2016. Firstly, the developer should concentrate on Fabric Energy Efficiency (which will be familiar to those of you who work with the Code for Sustainable Homes). This includes more insulation, less thermal bridges, better windows, good solar gain and a low air permeability rate.
Next, you need to look at low carbon and renewable sources to improve the overall emission rate of the building. This could come from solar panels, heat recovery options and low carbon fuels. So far, nothing ground-breaking as far as a routine SAP assessment is concerned.
But the third section is called ‘Allowable Solutions’; and this is where things start to change…
Let’s say you’re building a new house at 90sqm, and the expected Dwelling Emission Rate (following fabric and services improvements) is 10 kg/CO2/m2 or 900 kg/CO2. (There be a lower target to achieve for Building Regs, but we’ll work with assumptions for the purpose of this example – a typical gas heated house built to current regs is in the mid-teens).
It’s proposed the developer is given several choices about how to reduce the Dwelling Emission Rate to zero, effectively creating a zero carbon home (under the new definition!).
They could install enough renewables on site (such as PV) to reach a value of zero in SAP. In this example, we’d be looking at around 16sqm of PV.
OR the developer can leave the house as it is, go off to an existing house, and make the efficiency of that home better by 900 kg/CO2 to balance out the energy used by the new house. Basically, builders would have something like a bank account, but with a balance shown in carbon emissions rather than money. They could build up CO2 savings on renovations or by building a house with a negative emission rate, and take the balance over to their future projects.
Quite how this idea would be maintained, managed and policed isn't clear.
Alternatively, ‘Allowable Solutions providers’ could be established. These would be like the mortgage lenders of the emissions world. A builder could pay these providers to take over responsibility for the emissions of his latest project, and these companies would then channel the money into things like solar farms. Of course, the developer could cut out the middle man, and do the investing themselves.
The final option would be a simple payment to the local authority, based on the amount of emissions a new house is expected to produce. The consultation mentions a few costs (and remember this is all open to public comments) – the high end option being £90 per tonne of CO2 for thirty years. In our example, a house producing 900 kilograms annually would create 27 tonnes over three decades, and would therefore cost the developer £2,430. If the SAP assessment was improved to an emission rate of 9, this fee would drop to £2,187.
It would be feasible to create a mix-n-match of the above options. If the above was to become law from 2016 onwards, what approach would you take?