BCD 2019

148 T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 1 9 C AT H E D R A L C O MM U N I C AT I O N S at Schönbrunn Palace in Vienna, where all services are contained in a pole. These include an electrical socket, emergency light, speaker and a sprinkler head (illustrated opposite). When considering the provision of sprinkler protection in a building it should be remembered that, while sprinklers are very effective at controlling fires, they will have no influence over whether or not ignition takes place. The presence of sprinkler protection does not eliminate the need for preventative measures to reduce the risk of a fire occurring. Sprinkler protection is very advanced in Scandinavian countries, where wooden buildings predominate. Following the serious fire that spread to a number of wooden merchant houses in Bergen in the 1950s, the remaining houses were fitted with internal and external sprinklers to prevent fires from spreading to their neighbours (illustrated above). It can be seen that with these external systems the sprinkler heads are upright, which allows the pipework to be drained during the winter to prevent freezing. The pipes are then pressurised with air and when a bulb is broken by heat the air is expelled allowing the water to flow. If the pipes are kept dry all year round it is called a dry system and if it is wet during the summer it is called an alternate system. Because of the temperature extremes in Norway, they have developed a dry pipe water mist system called Fogtube where the water is supplied by fire engines. The Fogtube has an inlet for the fire service hose and 15mm copper tubes are fixed in the loft. The tube has two slits cut into it at 45 degrees to each other, so water emerging from them creates a mist that has a mixture of droplet sizes (illustrated above). A fire test was carried out just north of Trondheim in 2004 which proved the system’s effectiveness. A wooden farmhouse was fitted with a Fogtube in the loft, and holes were formed in the ceilings of the lounge and bedroom to allow the fire to spread vertically. A fire was lit in the lounge and reached flashover, then spread to the bedroom which also reached flashover but it was prevented from entering the loft by the water mist. This proved the theory that the loft would remain intact while the rest of the house burnt down. Dry systems like this may also be appropriate for heritage buildings where the risk of accidental leakage is the principal deterrent. However, the ability of a sprinkler system to respond automatically and control a fire is of particular importance in rural areas where the building may be far from the nearest fire station, which will lead to some delay in firefighting operations being commenced by the brigade. Some of the fire stations may be manned by retained (part time) fire crews, which typically results in a delay when compared with stations manned by full time staff. Also, if the retained crew were already responding to a fire situation the call would have to go to a fire station further afield. A sprinkler system is not intended to cope with a fully developed fire which may enter the sprinkler protected area from an adjacent part of the building with no system in place. Therefore, if sprinklers are to be installed, they should ideally be installed throughout the whole of the building in question. If installed selectively, as can happen in an historic building, physical barriers to control the spread of fire into the sprinkler protected compartment would be required. In such cases the sprinkler system would be designed to protect the room or compartment of origin. The cost of installing a sprinkler system in an historic building varies depending on the type and size of the building, its form of construction and use, its location, the type of sprinkler system to be installed, and the ease of access to areas in which pipes and sprinkler heads are to be installed. The cost of sprinklers is often compared to the cost of a good quality carpet, but this does not take into account the pumps and tanks, nor the additional costs that arise in occupied buildings where furnishings and fittings have to be moved and stored. In heritage buildings with historic collections this is a specialist operation requiring careful documentation, handling and storage, and skilled conservators may be required for the lifting and reinstatement of floor boards and other historic fabric. This could be four times the cost of the system itself. It will be more economical and less disruptive to the fabric of the building if the installation of sprinklers can be carried out at the same time as other services are being renewed. If an organisation has a number of buildings it would not be feasible to fit sprinklers to all of them, but prioritising the requirement is problematic. Should the one which is most vulnerable come first, or the one with the highest insured value? As with all issues connected with fire prevention and protection, the key is to understand the risks. STEVE EMERY is theOxfordUniversity fire officer and chair of the Institution of Fire Engineers Special Interest Group for Heritage Buildings (steve.emery@safety.ox.ac.uk ). He takes a keen interest in finding ways of protecting heritage buildings from fire, while avoiding damage to the things that make them important. A pole in Schönbrunn Palace in Vienna combining sprinkler, emergency lighting and other services External protection of jettied timbers and recessed wall, Bergen Sprinkler protection of roofs in Bergen: the exposed pipework is filled with pressurised air, and water rises only when a bulb is broken. A Fogtube spray in Norway which delivers water supplied by the fire service, allowing all the pipework to be kept dry

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