Book - School of Science and Technology

666 Running costsTable 23.4 Degree-day totals for the British Isles, 20-year averages a (1976±95), for a base temperature of15.5 CSeasonal totalsArea Annual total Sept./May Oct./AprilThames Valley (Heathrow) 2033 1941 1777South Eastern (Gatwick) 2255 2117 1907Southern (Hurn) 2224 2075 1863South Western (Plymouth) 1858 1751 1579Severn Valley (Filton) 1835 1752 1594Midlands (Elmdon) 2425 2264 2026West Pennines (Ringway) 2228 2079 1862North Western (Carlisle) 2388 2200 1940Borders (Boulmer) 2483 2253 1954North Eastern (Leeming) 2370 2201 1955East Pennines (Finningley) 2307 2144 1912East Anglia (Honington) 2254 2108 1895West Scotland (Abbotsinch) 2494 2283 2017East Scotland (Leuchars) 2577 2351 2053NE Scotland (Dyce) 2668 2418 2102NW Scotland (Stornaway) 2671 2374 2032Wales (Aberporth) 2161 1984 1751N. Ireland (Aldergrove) 2360 2169 1909Dublin 2322 2135 1897Cork 2027 1864 1650W. Coast Ireland 2188 1979 1738a Source CIBSE Guide Book ATotals for Republic of Ireland are a 9-year average (1961±70). (For current records refer to MET EÂ ireann.)Period of useHere it is necessary to make assessments of the period of occupancy of a building and thelength of time during which the heating system will be at work. It is clear that a finitedistinction must be made between the two and although the former may be defined withease, the latter will depend upon the particular characteristics of each individual buildingstructure and the system associated with it. It is the response of the structure to heat inputand the varying abilities of any one of a variety of systems to match that response which isimportant, as has been discussed in earlier chapters.For the heating system, the hours of use may be considered in terms of periods per year,per week or per day. For the yearly use, as has been explained previously, a figure of 30weeks is that most commonly assumed for commercial and industrial premises. Since, asillustrated in Figure 23.2, the diurnal external temperature range in May and September issuch that early morning and evening heating may well be required in houses, flats, hotelsand hostels, etc., a 40 week season is likely to be more appropriate in these instances.The weekly use again depends upon the kind of building and type of occupancy.Domestic premises, hotels and the like require service over seven days; commercial andindustrial buildings need not be heated for more than five days and no more than one ortwo day usage is normally considered for churches, village halls and the like. For dailyuse, similar conditions apply and it will be appreciated that continuous heating over 24hours each day is very rarely required. The shorter the period when service is provided,