20 April 1998

Jake Chapman, Managing Director, National Energy Services Ltd.

Talking to The Millennium Debate

The energy rating scheme

An energy rating of a house is a way of reflecting its energy performance, rather like a miles per gallon figure for a car. The energy rating is produced by an assessor or surveyor going to a house and surveying it in terms of energy features such as insulation, type of heating system, type of controls, how the water is heated and so on. All that data is fed into a computer programme, which, based upon the data and the way the house is used, can predict the energy use of the house. So the energy rating is actually based upon all that data plus assumptions about an average family using the house.

The computer programme calculates the costs of all the fuel that will be used, and works out an index based upon the cost per square metre. So the energy rating of a house varies from 0 to 100; with 100 being the best and 0 being really awful, and much too expensive even to be usable.

Energy ratings are currently widely used in social housing, and are compulsory for all new housing and will, if current legislation goes through, shortly be required as part of all valuation surveys in this country.

Although in the future, lenders may not do as many valuation surveys as at present, most people expect that where the lender does not carry out even a valuation survey, many of the buyers will require such a survey to be carried out, for their own peace of mind. At the moment, buyers get a large measure of reassurance from the fact that the lending organisation has carried out the survey, and even if they do not tell them the full results, the fact that they are prepared to lend money against the survey gives them some measure of reassurance. If they know that no survey has been carried out, I think more people will actually get one done off their own bat, and will then similarly get an energy report and energy rating information.

One of the reasons why legislation has been necessary is because the lenders have not found a way of making money out of providing this service. However, once they have all invested in the necessary training and systems to provide the service, the cost of doing it for somebody who is outside the scope of the legislation is extremely small. It has been estimated at 10. So they could actually charge people 10 or 20 for it and at least cover their costs. What they have resisted so far is investment to set the systems up in the first place, and that is why the legislation was necessary – to get them over that hurdle.

How long have you been carrying out this computerised work of energy survey?

I personally started a business in 1983, which was doing exactly that, but on a private basis. By 1985 we had developed an energy rating scheme for the Milton Keynes Development Corporation, which by 1988 was a compulsory part of all new house building in Milton Keynes. So that sort of scheme has been around for 15 years, and on a large scale for the last 10 years.

How reliable is the programme – obviously it depends what you put into it in the way of data – but is the end result generally reliable, and how reliable?

Yes. If you put accurate data about a house into the programme, you will predict within at least 10% the running costs for an average family. The key is actually the "average family", because everybody uses a house very differently – there is no such thing as an average family with 2.3 children. We have extended the software over the years, so that you could put in exactly how the occupants use the house, and then you find that again you can predict their fuel bills to within 10%. So when we say somebody’s fuel bill is 500, they could be as little as 450 or as much as 550, but 500 is a good estimate.

How would you know the exact thermal quality of the structure of an existing building?

We don’t know the exact properties of this. We assume that the building was constructed to meet the building regulations applying at the time when it was built. So we have standard U values for each type of construction in each period of building regulations. Then in other cases, like the loft insulation which people may have topped up, you can go there and you can look at it immediately. Things like wall constructions, where it is very hard to identify the actual U value, we do it by that process of age and type of construction.

I can see now how you can do it in 10 minutes, or for 10, when the computer is doing all the work, and it’s already programmed to do it.

The computer’s doing a lot of the work. When you put the post code of the house in, it knows the area of the country it’s in, the height above sea level, etc. From very little data we actually get an awful lot of information about the energy properties of the property and where it is in the house, and so on.

Do you actually develop the computer programme yourself?

I did initially. It was something I started in 1983, but it’s now got 30 people employed in it, about ten of whom are computer programmers. And there is a lot of development work continuing, monitoring existing houses, getting the predictions better, and coping actually with a lot of the new technology which continues to come along, new types of heating control, new types of boilers, even new methods of insulation.

So you would actually supply a computer programme disk to a surveyor?

There are various ways that we do it. One way is that the surveyor could actually have his own computer programme on his laptop. Or he could fill in a data form which he could then fax back to some centre for processing. Or he can collect the information on one of these little hand-held devices and send the information off to be processed by e-mail. There are lots of different ways that the data can get transferred from the surveyor at the house to the calculation end, hence to a report that the final consumer receives.

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