In support of electricity

We have already reached the stage at which bedrooms, some living rooms, kitchens and office spaces have fabric losses at design conditions which are less than the normal internal gains. In addition, air-to-air heat reclaim units are approaching the stage at which fabric losses plus net ventilation losses are also getting close to the internal gains.

We are already substantially electrically heated, whether we like it or not, and the operating hours in which genuine heating is required are becoming very few indeed. Close control of electrical heating is very simple and more accurate than close control of wet systems too, so the remaining problem with electrical heating is the peak pattern of weather-related national demand.

The largest HVAC energy consumer for which there is still an open choice of energy supply is domestic hot water supply. The overriding question is whether point-of-use water heaters should be mandatory, simply because summertime storage losses from other systems are not acceptable. This choice being made, other factors such as the embodied energy, transmission losses and energy used by support services should be brought into the argument.

The uses of electricity that still bear much closer examination are those that use the kWhs rather than those that require the peak kWs. Fridges, freezers, and in many households PCs and some lighting, run 24 hours a day.

Surely Category A energy efficiency for these “white goods” and lighting fittings should therefore be mandatory and billing should reflect the desirable 24-hour usage pattern. In offices, photocopiers and communications equipment must be added to this list. Over the course of 24 hours, the so-called office small power consumes up to 50% of the floor total, with lighting using the rest.

John Moss, consultant to Arup R&D.