Building Services

It is a well-known fact that hot air rises and that its place is then taken up by colder air. This natural effect occurs because the density (mass/unit volume) of the rising column of hot air is less than that of the falling column of cold air. This process in its continuously operating mode is encountered in any naturally vented enclosure and also in any chimney that is functioning properly. It is referred to as the ‘stack effect’.

Air conditioning may be defined as a system or process for controlling the temperature, humidity and cleanliness of air. The term ‘humidity’ refers to the amount of water vapour which can be ‘carried’ or ‘supported’. It is found that warm air can support more water vapour than cold air and whereas warming air is a simple process, cooling it is more complicated, requiring the use of special-purpose plant. The warming or cooling of air is usually carried out by arranging for it to flow over a collection of tubes, sometimes referred to as a ‘nest of tubes’, or a heat exchange battery. The area of surface available for any heat exchange may be increased by attaching circular fins to the outside of each tube along its length. The substance producing the heating or cooling is then passed through the inside of the tubes.

In some parts of the earth’s interior, energy is produced from the decay of the radioactive isotopes of uranium, thorium and potassium. It is known that energy at a temperature suitable for space heating is to be found in underground reservoirs of hot water (aquifers) and also in hot dry rocks (HDR).

A typical pipework layout, with controls, for a gas-fired atmospheric burner attached to a domestic boiler is shown in figure 4.1. An atmospheric burner is one in which the air for combustion is naturally aspirated and the pressure inside the boiler combustion chamber is just below atmospheric. The inclusion of a draught diverter in the flueway just above the boiler ensures that any change in the draught pressure which may occur will not materially alter the pressure inside the boiler combustion chamber, or (in the case of an increase in pressure) extinguish the main flame and/or the pilot light.

The first application of central heating, where the source of heat is located some distance away from the area that is to be heated, is credited to the Lacedaemonians of Greece [5.1], who in 350 B.C. constructed a temple in Ephesus, in which hot gases, derived from burning lignacite, were passed through conduits built into the floor.

It has become possible for man to ‘generate’ electricity, and conversely, to produce a force from an electrical current, by making use of the information contained in the following statement: ‘when electromagnetic fields, such as those emanating from the opposite poles of a bar magnet, are moved by means of a force (acting at any angle), across an electrical conductor, an electromotive force (emf) is set up across the ends of the conductor’. Joining these ends to form a continuous loop will allow an electrical current to flow.

Those organisations responsible for the supply of potable water to buildings in the UK have the statutory power to make and enforce water bye-laws, which are designed ‘for the prevention of waste, undue consumption, misuse or contamination of water supplied by them’. Building Regulations deal with ‘aspects of safety’ and British Standards deal with ‘fitness for purpose’.

In England, during the period of the industrial revolution (1750–1850), steam power was applied to the operation of capstans, winches and winding drums used for moving and lifting loads. In the early 1800s, steam power was also used to pump water into a cylinder containing a ram, which was attached to a lifting platform. The stroke of the ram was equal to the height of travel and the cylinder had to be buried to an equivalent depth.