Stewart Kidd looks at the benefits of and hurdles faced when fitting fire suppression systems in historic and heritage buildings
While all modern buildings include the provision of a range of fire safety measures intended to protect the lives of occupants should a fire occur, these are not things that can be taken for granted in the case of structures built before about 1939.
Current building standards demand that occupants in all parts of any building, including dwellings, can exit the premises or reach a place of safety by their own efforts, without the aid of tools or specialist knowledge. However, problems arise where an existing building is to be subject to a major refurbishment or where a change of use is to take place, known as ‘adaptive reconstruction’.
Either of these situations usually brings with them a need for compliance with the latest version of the approved handbooks to the Scottish Building Standards or Approved Document B of the Building Regulations for England & Wales. Compliance with UK fire regulations requires:
- means of escape
- the structural protection of escape facilities and the structural stability of the building in the event of a fire
- the provision of access and facilities for the fire and rescue service
- early detection and warning of fire
- facilities for fighting fires
- an effective fire safety management regime.
Traditionally, these have been imposed on new or refurbished buildings under Building Standards or by requirements imposed on the building occupier by fire regulations.
The essential elements needed for safe egress in the event of fire mandated by the regulations and standards include:
- early warning of fire – except in the very smallest building this will usually involve the provision of automatic fire detection
- exit signs to indicate the way out of the building
- adequate lighting to illuminate the ways out of the building, including escape lighting in case there is a failure of the electrical supply
- door hardware which permits easy and swift access – even where doors are locked for security purposes
- doors which open in the direction of travel in the case of buildings where the occupancy capacity exceeds a specified number.
These provisions are relatively simple in new buildings and follow a well-established set of principles, however this is not always the case where such requirements need to be provided in traditional buildings - especially where the building is being modified or refurbished for a change of use.
Problems of adaptive reconstruction
A good example of the issues which need to be considered can be demonstrated by taking the example of the conversion of a listed 19th-century office building into an hotel. The fire risk assessment regimes currently in use in the UK adjudge that the highest risks to occupants relate to the following categories of people:
- persons asleep
- the very old or the very young
- persons not familiar with the layout of the building
- persons who may have disabilities or may not understand English well
- persons whose senses and abilities may be impaired due to the use of alcohol or drugs
- large numbers of persons.
Clearly, the occupants of any hotel will include many or all the above groups and as such, hotels have always classified as among the highest risk occupancies. This is why hotels were closely controlled by the fire certificate process under previous fire safety legislation.
How then can one make the required fire safety changes to a listed building to permit its use as a hotel without wide scale destruction of the authenticity of the features which make it worth listing?
To apply the strict criteria set out in building regulations in a refurbished building, some or all of the following may be required:
- fire rated doors on all bedrooms and utility rooms
- upgraded fire barriers around certain high hazard areas such as linen stores or catering kitchens
- installation of fire dampers in ventilation and extract ducting where this passes through a fire barrier creation of smoke lobbies on each floor
- sub-division of long corridors by smoke stop doors
- creation of additional fire exits or escape stairs
- installation of a fire alarm and detection system with fire sensors in most rooms and compartments – this would also require installation of alarm sounders throughout the building (especially in bedrooms), as well as the fitting of fire call points on exit routes and near each storey exit
- installation of a range of signs including exit and fire action signs
- installation of escape lighting
- provision of portable fire extinguishers and/or fire hose reels
- adaptation of doors to open in the direction of escape
- exit doors across escape routes which can be opened at any time even when normally secured against unauthorised access
- provision of access routes and facilities for the fire and rescue service (which could include a firefighting shaft, installation of a dry riser system, a supply of firefighting water, access to the exterior of the building for fire appliances and suitable areas for positioning these).
Any or all of these provisions could be a factor which could act negatively on the authenticity, appearance, value, and interest of the building. Some, like driving a new staircase through the heart of a building could be so destructive of historic fabric that they should not normally be contemplated.
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, its earning capacity, and its real estate value. For a listed building, the same criteria will be addressed, but in a way that causes minimal or no damage to whatever gives the building its special quality. 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; the same aim of the protection of life and property, but with different constraints for decision-making. 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?”, and whilst “everything” might be an obvious response, the answer 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:
- essential – The fire systems should be central to meeting the objectives of the protection of life, buildings, and contents
- appropriate to risk – Any system that is installed should be apposite to the risks being considered
- compliant with legislation – Systems should be installed according to demonstrable performance-based and other legislatively prescribed standards of safety
- minimally invasive – The retrospective fitting of fire systems should involve minimal degrees of physical intervention on the historic structure
- sensitively integrated – Installed systems should be designed to be integrated sympathetically with the historic fabric and its detail
- reversible – Fire systems should be installed, where possible, according to a reversible, ‘plug-in, plugout’ installation philosophy.
Use of fire suppression systems
It is suggested that recent experience 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. An example from Scotland is the case of Corgarff Castle, a Scheduled Ancient Monument and Grade A 17th century property in the care of Historic Scotland.
Here, the installation of an automatic fire suppression system provides multiple benefits. It compensates for a compromised means of escape (in the form of a single timber staircase). It also enables the premises to comply with current fire safety legislation for a property open to the public, and gives protection for an asset with no on-site fire water capacity and with very restricted fire service response for three months of the year due to its geographical location.
The unique benefits of automatic fire suppression and firefighting systems are that they not only detect and notify the presence of a fire, but 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.
Indeed, in many cases the system will often manage to extinguish the fire before the arrival of the fire and rescue service. The damage minimisation potential of suppression systems is especially beneficial in the heritage buildings context where historic fabric or contents may be irreplaceable.
There are several different automatic fire suppression and firefighting systems available employing different extinguishing equipment, techniques, and firefighting media. The suitability of each type of protection system for specified circumstances will be determined by several factors including the type of fire likely to be encountered in the protected space. BS 5306-0 (2020) provides impartial guidance on the selection of appropriate type of system for specified properties.
Water-based systems
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 first is the sprinkler systems and the second the water mist system. They are radically different in design, cost and application and so will be considered separately.
Sprinkler systems
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 whilst a primitive form of sprinkler system is known to have been installed in the Theatre Royal, Drury Lane, London as early as 1812.
Often, objections are raised to the installation of sprinklers on the grounds of potential water damage. However, 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 required. Water damage incurred from a sprinkler system reacting immediately to control fire growth, or in many cases to extinguish it altogether, will be relatively tiny when compared to the later application of water from fire and rescue service hoses to fight a developed fire.
Concerns about water leakage from heads and distribution pipework are also frequently aired. In fact, a properly installed sprinkler system should be less likely to leak than any other water supply service within a building as the components of the system will have been subjected to a rigorous quality assurance regime and are listed by a third-party certification body. The designer and installer of the system will also have been subjected to the scrutiny and approval process of the appropriate certification body.
As a final safeguard, systems are provided with an automatic alarm to give local warning of any water flow in the system. This alarm is water powered and so independent of an electrical supply. Modern systems also have an electrically operated water flow alarm valve which is connected to the fire detection control panel to notify the fire and rescue service.
In heritage protection, Scotland has pioneered the use of water-based fire suppression systems to protect historic buildings and a significant body of experience has now been built up in relation to designing and installing these systems in a sympathetic and non-intrusive way. Buildings known to be protected so far include Duff House in Banff, the National Library of Scotland in Edinburgh, Newhailes House in East Lothian, and Broughton House in Dumfries and Galloway, as well as the aforementioned Corgarff Castle in West Aberdeenshire.
Sprinkler systems should be designed and installed in accordance with BS EN 12845-1 Fixed firefighting systems – Automatic sprinkler systems: Design, installation and maintenance (2019) (under review). Domestic and residential properties (for example, residential care homes, hostels, and school boarding houses) can be protected by sprinkler systems designed and installed to BS 9251:2020 Sprinkler systems for residential and domestic occupancies. Code of practice. Note that sprinkler systems in hotels and boarding houses and like premises should be installed to BS EN 12845:2009.
Water mist systems
The only other water-based system which would be appropriate for traditional buildings would be water mist. Benefiting from recent research and proprietary development, water mist systems, employing heads discharging water in a mist or fine spray, superficially appear very similar to conventional sprinkler systems. Indeed, these systems offer many of the benefits of conventional sprinkler protection.
Several proprietary systems are available ranging from very high pressure (up to 300 bar) systems producing a fine water particle mist, to low pressure systems providing a fine water spray extinguishing medium akin to a conventional sprinkler system. The water is propelled either by pumps or by an inert gas and dispensed from nozzles that are designed to deliver water in fine droplets to the area of fire. The suppression mechanism relies on a combination of cooling by the water, the production of steam that displaces oxygen from the area of the fire to a level that cannot sustain combustion, and inhibition of the chemical processes of combustion.
In comparison with sprinklers, water mist systems use comparatively small amounts of water to fight a fire, and this means less water needs to be stored. A further benefit is the minimisation of water damage in the event of activation.
At the time of writing, there are three standards for water mist systems:
- BS 8458 for residential/domestic buildings
- BS 8489 for all other buildings
- BS EN 14972-1.
Much research has been undertaken into the appropriate use of these systems in confined spaces and large-volume areas. High-ceilinged rooms with large floor areas may prove a significant problem in designing the nozzle layout to ensure potential fire locations fall within the effective range of the nozzle distribution – although 6m high rooms in Stirling Castle are currently protected with a water mist system.
Tests have also indicated that the design of water mist systems needs careful consideration where the protected location is prone to significant air movement as this may impact on the effectiveness of the mist. Mist systems are also less effective at extinguishing slow, deep-seated fires in ‘normal combustibles’ than traditional sprinkler systems. For instance, in one test trialing water mist protection in cellular archive storage areas the results were disappointing.
Conclusion
In many cases it is possible that significant benefits can accrue where a fire suppression system is installed in a historic or heritage building which is being refurbished or modified for a change of use. Apart from providing compliance with current building standards and making it easy for the building to meet fire safety standards, a fire suppression system may do less damage and be less intrusive than the conventional approach to escape routes and compartmentation.
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Stewart Kidd is a Consultant at the Loss Prevention Consultancy and Chair of the BAFSA Watermist Working Group