Book - School of Science and Technology

122 Electrical storage heatingTable 5.1 Recommended design values of rates for ventilation loss by natural infiltration in multi-storey officebuildingsVentilation loss (W/m 3 K)Height of building15m and underOver 15mType of building Day Night Day NightBuildings with little or no internal partitioning (i.e. `openplan' buildings), or with partitions not of full height, orbuildings with poorly-fitting windows and internal doors 0.5 0.3 0.7 0.3Buildings with internal partitions of full height, withoutcross ventilation, and having self-closing doors tostaircases, lift-lobbies, etc. 0.3 0.2 0.3 0.2NotesThe basic design temperature should take into account the fact that there is no inherent reserve and a basic temperature ofsingle-storey buildings, and 1:7 Cto 1:1 C for multi-storey buildings is proposed.3:3 CforChapter 2 but making allowance for a reduced rate of air change during the night:Table 5.1 quotes recommendations in this latter respect for multi-storey office buildings.This 24 hour heat requirement would then be divided by the number of hours (normally7) during which energy input is available, the product being the appliance ratingrequired. That is:R 1 ˆ (24 Q/n)whereR 1 ˆ equipment rating (kW)Q ˆ design heat loss (kW)n ˆ available charging period (hours)Such an approach does not, however, take account of a number of the other considerationswhich were discussed in Chapter 2, many of which are particularly relevant to amethod of heating which is subjected to an intermittent energy supply associated with anoutput which, although at a level which varies, is continuous. The thermal response of thebuilding structure which is related to its mass; the level of insulation provided; the area ofglazing; heat gains during the hours of occupancy from lighting and occupants are allrelevant as is, where applicable, the degree of output control available. The complexitiesof these aspects are compounded in instances where output is primarily radiant and thus isinteractive with other surfaces `seen' by equipment or system. Calculations based uponconsideration of all these variables would be out of the question for individual applicationssince, in any event, meticulous accuracy would be misplaced when applied toselection from a finite range of production equipment. Use is made therefore of correctionfactors, part theoretical and part empirical, which are applied to the simple equationnoted above. These cover the following aspects: