A central issue that the Coalition needs to get to grips with in the formulation of the Green Deal is how the financial savings from energy saving measures are calculated. Currently we use tools like SAP and RdSAP to assess the imnpact on properties, but these are extremely crude mechanisms compared to, say, a Dynamic Thermal Simulation. This is very important because whatever tools are used they must work across the UK and take account of the fact that there are many more degree days of heating in the Borders than in Cornwall. This is something that SAP conveniently ignores for new buildings. This matters, but it is not politically significant. Selling Green Deal advice to residents which turns out to be wrong is very politically significant because the advice will be sold to 24 million odd householders, i.e. nearly every voter in the country. The potential for political fallout is huge. Residents who are sold a package of measures and then find out that they are not making the savings that they were advised that they were going to make will be very unhappy indeed, particularly if the reason turns out to be that the tools for assessing the savings were not really up to the job.
I estimate that we have about eighteen months to sort this out before the Green Deal goes live. We need an energy saving measures tool that is capable of assessing the impact of a set of measures, about one hundred measures, some with many variations, i.e. a boiler selection, and applying those measures to an ‘actual’ property, with an ‘actual’ family living in it, and in an ‘actual’ location. Only then will we have a tool that we can use to advise real families what the impact of the measures will be on their home, their lifestyle and their pocket.