With the passing into legislation of the Green Deal comes a few headaches to resolve. Among them is the vexed issue of how to calculate energy savings. The proposed method is to use a revised version of the Standard Assessment Procedure ( SAP) which can deal with the many permutations of homes, their energy performance before and after work is done and the cost of energy used and saved. All of these are issues that SAP is designed to deal with. The catch comes when SAP starts to be used as a basis for the Green Deal in promising energy savings. These energy savings are the basis for the Green Deal and without them there is no real way to assess whether measures will pay for themselves. But in order to be accurate SAP has to take into account where the home is, what its solar gains and losses are, how big it is, and where it is in the UK. This last element is important for the calculation of renewable energy as it will indicate the real performance of renewable technology in different parts of the UK. Isn’t this how it works now for newbuild?
No! it isn’t. The energy performance of all newbuild in the UK is based on the East Pennines! Why? Because if housetypes are not based on a single location and are based on regional weather then housebuilders would have to have different housetypes for different parts of the UK. The result of this would be that homes in the North of England would have to have higher levels of insulation to deal with more degree days, and homes in the South East would have less because of a lower number of degree days and higher levels of solar gains. Homes in the North would be more expensive to build, and homes in the South East would be cheaper to build. Profit margins in the North, which are already marginal would sink even lower, but would rise in the South where they are already high.
All this sounds like a conspiracy to make homes in the North less affordable, but if we are to base our housing policies on science, then this is the inevitable future. In an ironic twist, the fact that the Green Deal is going to be based on regional weather means that Green Deal projects in the North will have a quicker payback because the same insulation there will pay for itself more quickly by saving more energy than the same insulation in the South. You win some you lose some.
Introducing regional weather into SAP for the Green Deal signals to me that it is only a matter of time before it appears in new-build SAP. To do otherwise will be obviously wrong, both from a scientific perspective and from an economic one. When a housebuyer in the South buys their home they are not getting the truth from their EPC, any more than a housebuyer from the North. The only one getting the truth is the rare buyer in the East Pennines.
Interestingly, in a recent project, I was able to convince Building Control that by introducing regional weather into a manual SAP calculation that a renewable system was sufficient to pass the required target, even though SAP says that it isn’t. In my opinion this approach should be used by assessors where they feel that there is a convincing case to do so. But it shouldn’t be necessary. SAP should be based on the accurate location of the building, not on a location chosen for the convenience of housebuilders.
“The Truth”, as Mulder is so fond of saying, “is out there”