Book - School of Science and Technology

Chapter 2ThebuildinginwinterAs a general principle when approaching the question of space heating, it is desirable thatthe building and the heating system should be considered as a single entity. The form andconstruction of the building will have an important effect not only upon the method to beadopted to provide heating service, but also upon subsequent recurrent energy costs. Theamount of heat required to maintain a given internal temperature may be greatly reducedby thermal insulation and by any steps taken to reduce an unwanted intake of outside air.Large areas of glass impose very considerable loads upon any heating system and runcounter both to the provision of comfort conditions and to any prospect of energyefficient operation.The mass of the building structure, light or heavy, has a direct bearing upon the choiceof the most appropriate form of system since, in the former case, changes in externaltemperature will be reflected very quickly within the building and a system having aresponse rate to match will be the one that is most suitable. On the other hand, a buildingof traditional heavy construction may well be best served by a system which produces aslow steady output. Tall, multi-storey blocks of offices and dwellings introduce problemsrelated to exposure to wind and solar radiation as well as those related to chimney or stackeffects within the building itself. The form and design of the heating system must takethese aspects into account.Extraneous influencesWithin the space to be heated, the energy which is consumed by electrical lighting and bya variety of other items of current-consuming equipment will be released, as will heat fromthe occupants. The total of these internal emissions will contribute in some measuretowards maintenance of the desired space temperature. In addition, even in winter, heatfrom the sun may sometimes be enough to cause problems of excessive temperature inthose rooms exposed to radiation, while at the same time others, in shade, are not sofavoured. These fortuitous effects cannot be overlooked, although it is not possible to relyupon them to make a consistent contribution.It is a matter of importance to consider how far these heat gains should be taken intoaccount: if they are ignored, then the heating system may be so oversized that it will beunwieldy and will rarely, if ever, run at full capacity. On the other hand, if certainreasonable assumptions are made as to the proportion of the total gains which will