C O N T E X T 1 1 3 : M A R C H 2 0 1 0 29 approach to risk-based design where designers can take account of varying physical and human factors. Third, the ‘fire safety engineering’ approach.This is the level for which BS 7974 2 is provided.This provides an alternative approach to fire safety and can be the only practical way to achieve a satisfactory standard of fire safety in some large and complex buildings, and in buildings containing different uses. Caution should be exercised in adopting this approach without specialist input from a competent fire engineering practice. In most of their work, conservation architects will try to achieve a balance between the simplest, most cost-effective means of minimising the risks of fire and the effect of these on the building’s occupants, usefulness, earning capacity and real estate value. For a listed building, exactly the same criteria will be addressed, but in a way that minimises the impact on its significance. Effectively, this is a readjustment of the standard decision-making process. Rather than simply accommodating fire measures to the building’s usefulness or economic value, the design takes the preservation of the existing fabric and aesthetic into consideration. This conservation approach is effectively a brief-within-a-brief. It has exactly the same aim – the protection of life and property – but with different constraints for decisionmaking. In effect, the normal design process is given an unaccustomed focus by the overlaying need to conserve and protect the interests of posterity. The most difficult question any owner of a traditional property undergoing adaptive reconstruction can be asked is: ‘what would you wish to have left after a fire?’ While ‘everything’ might be an obvious response, the answer in reality needs to consider a complex set of interlinked issues, including the safety of the building structure, the contents of the building and, crucially, human safety. Achieving this balance requires careful consideration of some of the basic principles of fire protection measures such as detection and suppression systems. Primarily, any insertion of fire protection systems (or indeed, any other modern systems or equipment) in historic buildings should be: 1. Essential. The fire systems should be central to meeting the objectives of the protection of life, buildings and contents. 2.Appropriate to risk. Any system that is installed should be apposite to the risks being considered. 3. Compliant with legislation. Systems should be installed according to demonstrable performancebased and other legislatively prescribed standards of safety 3. 4.Minimally invasive. The retrospective fitting of fire systems should involve minimal degrees of physical intervention on the historic structure. 5. Sensitively integrated. Installed systems should be designed to be integrated sympathetically with the historic fabric and its detail. 6.Reversible. Fire systems should be installed, where possible, according to a reversible, plug-in, plug-out installation philosophy. Recent experience (much of it in Scotland) of the installation of fire suppression systems makes it clear that in many cases a well-designed fire suppression system can compensate for a range of deficiencies in areas such as means of escape and means of containing fire and smoke spread. In the case of Corgarff Castle 4, a scheduled monument and Grade A 17th century property in the care of Historic Scotland, the installation of an automatic fire suppression system provided multiple benefits. These are: • compensation for compromised means of escape in the form of a single timber staircase • enabled premises to comply with current fire safety legislation for property open to the public • protection for an asset with no on-site fire water capacity and very restricted fire service response for three months of the year. The unique benefits of automatic fire suppression and fire-fighting systems are that they not only detect and notify of the presence of a fire, but they actually fight the outbreak. A properly designed, installed and maintained system will, at the very least, contain a fire to a small area and consequently reduce the extent of damage. In many cases the system will extinguish the fire before the arrival of the fire and rescue service. The damage minimisation potential of suppression systems is especially beneficial in heritage buildings where historic fabric or contents may be irreplaceable. A number of automatic fire suppression and firefighting systems are available, employing a variety of extinguishing equipment, techniques and fire-fighting media. The suitability of each type of protection system for particular circumstances will be determined by a number of factors, including the type of fire likely to be encountered in the protected space. As an inert, low-cost, extinguishing medium which is plentifully available, with minimal impact on health and safety and the environment, water is probably the most readily recognised extinguishing medium suitable for the majority of fires. There are two main types of water-based systems: the sprinkler system and the water mist system.They are radically different in design, cost and application. Sprinklers are one of the oldest forms of firefighting technology, having been in use for over 140 years. The earliest recognisable installations were in British and US cotton mills between 1852 and 1860. A primitive form of sprinkler system is known to have been installed in the Theatre Royal, Drury Lane, London as early as 1812. Objections are often raised to the installation of sprinklers on the grounds of potential water damage. Contrary to popular perception, only the sprinkler heads in the immediate vicinity of the fire operate, so the amount of water released to suppress the fire is kept to the minimum. Water damage incurred from a sprinkler system reacting immediately to control fire growth, or in many cases to extinguish it altogether, 2 BS 7974: Application of fire safety engineering principles to the design of buildings. Code of practice 2001 3 Most importantly, this means that where appropriate, listed building consent must be obtained before any work is undertaken, and this applies even to work mandated by the building control or fire authority. 4 Kidd, S: Castle Issues – Sprinklers in a scheduled ancient monument, ‘Fire Prevention and Fire Engineers Journal’, September 2007
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