Book - School of Science and Technology

Temperature difference 93equipment than does a straightforward heating system. Furthermore, it is probable thatsome spaces within an air-conditioned building may require heating, coincidentally with ademand from others for cooling, as a result of different orientation, time of day and thelevel of miscellaneous internal gains. This situation will prevail in particular during themid-seasons between summer and winter and it points to a very positive conclusion thatsystem controls must be considered in detail right from the earliest stages of design.Temperature differenceThe comments made in Chapter 2, with regard to the use of dry resultant temperatures,are equally valid for summer conditions but, for building envelopes which meet with thecurrent regulations as to their thermal properties, values from this scale may be taken asnumerically equal to air temperature without any need to confuse the calculation processby application of correction factors.Inside temperatureThe only comment necessary under this heading is that it is usual for summer designpurposes to make a distinction between continuous and transient occupancy, 21 C drybulb and 23 C dry bulb being the commonly accepted levels, respectively, with 50%saturation in each case.Outside temperatureAs was the case for winter conditions, the design temperature datum adopted to representoutside conditions in the British Isles will vary according to the precise location. Table3.11 lists the levels recommended in the 1986 Guide Section A2 for the same eight locationsgiven in Table 2.15. It will be noted that, in this instance, both dry and wet bulbtemperatures are given, as will be required for the design of air conditioning systems.When considering applications for buildings in town centres, it is good practice to usedry bulb temperatures one or two degrees higher than those listed in order to makeallowance for the heat island effect created by traffic etc.Table 3.11 Summer external design temperature (1986 CIBSE recommendations)TemperatureLocationMonthDry bulb a( C)Wet bulb( C)Diurnal range(K)Belfast July 23 17 8Birmingham July 26 19 9Cardiff August 25 18 7Edinburgh July 23 17 9Glasgow July 24 18 9London July 29 20 9Manchester July 26 18 8Plymouth July 25 19 6a The peak dry bulb temperature will occur normally at 15.00 hones GMT.