Fire Suppression in National Trust for Scotland Properties
|Aerial view of Newhailes|
Almost every year sees significant historic buildings being destroyed by fire and, although buildings can be rebuilt, original fabric is irreplaceable. In Scotland, over the last 12 years, one historic building has been lost per month by fire (1). The National Trust for Scotland is responsible for the protection of 128 properties, which include some of Scotland's finest countryside and wild landscapes as well as castles, country houses and gardens, and so takes the protection of our properties against fire very seriously.
While an automatic fire detection and alarm installation can raise the alarm and call the fire brigade as soon as it detects products of combustion, the extent of damage caused by the fire depends critically on the response time of the fire brigade. In rural areas the building may be remote from the nearest fire station, leading to some delay in the arrival of fire fighters to tackle a blaze. The installation of a fire suppression system provides an effective method of controlling a fire and an immediate line of defence. In many cases, where one has been installed, by the time the fire brigade arrives on the scene the fire is found to be extinguished. Where this has not happened, the fire spread has still been greatly reduced, providing vital assistance to the fire crew.
Sprinkler installations have been in use for many years, and they are familiar features of such buildings as shopping malls, retail warehouses, office blocks and supermarkets, but are rarely seen in historic buildings. This discrepancy may well be a product of commercial imperatives: downtime costs money and in the event of a fire within a sprinklered building, operations can usually be resumed within 24 hours. However, over the past ten years there has been an increasing demand for the installation of active fire suppression installations within historic buildings, mainly as owners of historic properties become more aware of the damage and loss caused by fire and the cost of having to rebuild. The fire at Uppark, owned by the National Trust, and the fire at Windsor Castle are two examples which have encouraged debate on the issue of loss after a fire.
Historic Scotland has been a key advocate for the use of fire suppression within its properties and has published Technical Advice Notes on fire protection as well as on the installation of fire suppression.
The National Trust for Scotland has installed automatic fire suppression systems in two of its properties, Newhailes near Musselburgh and Broughton House in Kirkcudbright and a third property is currently being considered for fire suppression.
The National Trust for Scotland acquired Newhailes House and its estate in 1997. Initial research and analysis demonstrated that the house derived its unique cultural significance from the complex interaction of different elements that together create a rich sense of place and a calming ambience. For this reason, the principal conservation policy for all work at Newhailes was to do as much as necessary to stabilise the condition of the buildings and the estate to prevent further deterioration, but no more, so that its special character is protected. This was a challenge for the Trust because, while leaving everything as undisturbed as possible, it still had to address the continuing deterioration of the house, the environmental conditions appropriate to the collections it houses, the safety of the public and staff, and the need for essential accommodation for staff and visitors.
|The library shown in a watercolour with its irreplaceable collection of books|
While seemingly at odds with this policy, the installation of a fire suppression system in the house was justified on several grounds, not least of which was the fact that if there were a fire at Newhailes then its unique significance could never be reconstructed nor could replacements for items within the collection ever be found. In this respect, the significance of its library was a particular concern. In addition, the existing escape routes were considered inadequate for the occupancy of the building, and the introduction of a fire suppression system would satisfy life safety requirements without the need for significant alterations to the fabric of the building. Newhailes House also exhibited all the limitations of historic buildings and collections in terms of combustible materials, voids in the structure, labyrinthine escape routes, and poor signage and escape lighting. However, the Trust's conservation policy for the house precluded upgrades to current fire standards.
After careful consideration of the arguments for and against (not least that the installation itself might destroy much of the intrinsic value and significance of the house along with interfering with the historic fabric) the Trust decided in favour of installing a system. This would enable Newhailes to be prepared for fire prevention at all times. The design criteria for the installation of the fire suppression system included minimal visual intrusion, sanctity of the visitor route throughout the house, and only limited lifting of floorboards. In addition there was to be no routing through plasterwork, cutting or repainting, and the pipe sizes throughout were to be as small as possible.
TYPES OF SUPPRESSION CONSIDERED
Of the principal fire suppression systems, dry powder and foam systems were not considered appropriate for Newhailes as dry powder is only suitable for local application (and not total room discharge), and foam systems present a problem where the discharged foam degrades to leave water containing a residue which could be harmful to building fabric and contents. This left Newhailes with three options which were duly considered; inert gas, water mist, and water sprinkler systems. The inability to hermetically seal Newhailes House as well as the unsuitability of gas in relation to occupation of the house ruled out a gas system, and while the water mist system was superficially attractive because it uses less water than a sprinkler system, the limiting choice of heads and the lack of British or European Certification standards on the system weighed against it. After carefully considering the advantages and disadvantages of the three systems, the Trust opted for a water sprinkler system as this had a proven record in historic buildings and offered the greatest flexibility in the choice (on both aesthetic and functional grounds) of heads.
The use of limited quantities of water to extinguish a fire is particularly important in the case of historic buildings because the consequences of saturating the fabric and contents of the building can be disastrous. Although water mist systems use less water than sprinkler systems, both types are much more economical in their use of water than the fire brigade.
|RATE OF WATER FLOW||TYPICAL DURATION||TOTAL WATER USED|
|FIRE BRIGADE – TYPICALLY
WITH FOUR APPLIANCES OPERATING
(2,000 litres/ minute each)
|90 minutes||720 m³
|AUTOMATIC SPRINKLERS – TYPICALLY WITH FIVE SPRINKLERS OPERATING*||350 litres/ minute (70 litres/minute each)||30 minutes||10.5 m³
|* In 26 per cent of fires only one head operates. Source: Historic Scotland Technical Advice Note 14 –
The Installation of Sprinkler Systems in Historic Buildings
A reliable water supply was essential, particularly as at Newhailes the sprinklers had a 'life safety' role, as well as protecting historic fabric. Therefore the water supply was duplicated to guard against the failure of one source, and also to help ensure that the supply would last at least until the fire brigade arrived.
The mains water supply had adequate pressure and flow, and was therefore suitable as one of the two supplies. The water authority also agreed that a second tanked supply could be connected to the public main as a private supply. The tank capacity required was 18,000 litres (4,000 gallons), sufficient for 20 minutes duration in the worst foreseeable fire, and without contribution from the mains. The pump and tank were located in a disused lean-to against the garden wall.
The mains water supply was set up to be the primary supply, switching over to the tank and pump should the sprinkler system pressure fall below the set minimum. A fire brigade pumping appliance inlet was provided for the brigade to supplement the supply or, in the event of the failure of the mains water and electricity supply, to supplant it with the 1,800 litres (400 gallons) carried in the pump alliance.
The pump room contains all the technical equipment to test the pressure and flow of the water supply periodically. All valves and monitoring devices are connected to the fire alarm system and to its permanently manned station.
|Left: under-floor pipework in the White Bedroom; Right: one of the contractors installing pipework in an attic room|
The pipework was executed in C-PVC plastic throughout, except where it was exposed. C-PVC (chlorinated polyvinyl chloride) is a light, tough, smooth and chemical-resistant alternative to steel, with less friction loss. It therefore permitted the use of smaller pipes than conventional steel pipework. As this system has glued joints, the entire installation could be completed in accordance with the Trust's hot works policy, without welding or any process involving a flame. In the basement corridor and vertical risers where the pipework was exposed, polished stainless steel was used instead.
|Detail of a sleeve resin bonded to a joist to allow the sprinkler pipe to retain movement|
The pipework was designed in multiple loops so that the water flow to an active head is always from two directions, again reducing the pipe size. The loops were also used for distribution and risers, reducing their size as well. A computer programme was used to assess the hydraulic performance of the system under all possible modes of operation, and this enabled yet further reductions in pipework sizes.
It was not the Trust's intention to do any redecoration within the house as the survival of 19th century decoration is so rare and significant that the Trust has strived to retain all existing surface textures. This meant that, while contractors were installing essential services, the only area of the building fabric that could be disturbed was the floorboards, many of which had been either lifted or replaced in the past. The zones exposed were used not only for the sprinkler installation but also for rewiring for power, electric heating, telephones and fire and security detection. Great care was taken in calculating routes for sprinkler pipes and other services to ensure that the structure was not further weakened by the inevitable cutting of joists, and where required a system with a sleeve and resin bond to the joist was used which allowed the sprinkler pipe to retain movement.
To minimise visual intrusion in the public rooms the aim was to use one sprinkler head per room. The sprinkler heads are from the Quick Response FR1 series made by RASCO (The Reliable Automatic Sprinkler Co). In these fittings the fusible (heat-sensitive) element is a 3mm diameter glass bulb, rather than a 12mm square solder plate. They were selected both for their small size and their slim yokes which could be turned so that the glass bulb, which is red, is virtually invisible to the eye. Heads with extended coverage were used in the principal rooms to minimise their number. Where placed against side walls (either on the ceiling or on the walls themselves), special heads were used which were designed to deflect the water towards the centre of the room, but most were mounted on the ceiling towards the middle of each room.
The sprinkler heads were not painted but retained in their original white as their visual impact was insignificant once all the collections had been returned to the buildings.
Throughout both the design process and installation of the fire suppression system, the Trust consulted widely, including with the insurers, the Loss Prevention Council and the fire brigade.
The fire suppression system at Newhailes has now been operational for four years. Given the tight constraints on the specification and design requirements for the system, the conclusion is that if sprinklers could be installed here, they can be installed in any historic building without damaging the historic fabric or the aesthetics of the rooms. The success can be gauged by the reaction of visitors to the house when asked what they thought of the sprinklers: they universally failed to notice them.
Due to the success of the installation at Newhailes, another Trust property, Broughton House in Kirkcudbright has also had a fire suppression installation as part of a major package of repairs. In 1901 Broughton was acquired by Edward Hornel, an artist of the 'Glasgow Boys' school. He became an avid collector of books, and in 1919 he embarked on a mission with a bibliophile friend to create for Kirkcudbright 'the perfect local library'. By the time of his death in 1933, the library had grown to over 15,000 volumes and spilled into every room of the house.
|Details of sprinklers in the library and in one of the bedrooms, illustrating the use of a deflector to project water towards the centre of the room|
Preventative conservation lies at the very heart of the Trust's purpose and tremendous effort was directed at introducing measures to improve the property's defences against major risks such as fire, theft, light damage and poor storage.
At Broughton, the house relies on local retained fire fighters with back-up from Dumfries, one hour away. In view of the risk this posed and the vulnerability of libraries to fire, the Trust decided that the best means of protection was to install a fire suppression system as part of the repairs package.
Although the conservation approach to Broughton was less challenging than Newhailes, there were much tighter constraints for water storage and controls, and it was agreed that there would be no water storage at Broughton, with all water being fed directly off the mains.
The requirements posed by fire suppression installations are among the most complex facing historic buildings, and their success depends on finding skilled contractors who understand the sensitivities of working with historic buildings. Unfortunately, there are few opportunities for contractors to gain the skills required as, despite successful installations at Newhailes, Broughton and several other important historic buildings in the UK, fire suppression within historic buildings remain unusual. As a result it could be some time before there are sufficient experienced contractors available for the countless country houses and stately homes in the UK that could benefit from these systems. However, the National Trust for Scotland has no doubt that sprinkler installations remain the only sure way to protect our historic buildings from the ravages of fire and it is only by sharing experiences and knowledge that skills and understanding can be developed.
Historic Scotland Technical Advice Notes:
11 Fire Protection Measures in Scottish Historic Buildings (2001)
14 The Installation of Sprinkler Systems in Historic Buildings (1998)
22 Fire Risk Management in Heritage Buildings (2001)
28 Fire Safety Management in Heritage Buildings (2005)
Historic Scotland Conference Proceedings:
Fire Protection and the Built Heritage (1999)
(1) Historic Scotland figures from Scottish press reports