Peter Caplehorn of Scott Brownrigg outlines the pros and cons of installing and operating sprinkler systems in domestic applications
The principle of using sprinklers as part of the fire protection measures in commercial and high-risk properties has been established for more than a hundred years. Recently there has been a move towards using them in domestic installations. This is due largely to acceptance by the authorities that these systems are a valuable contribution to safeguarding people and property, a maturing of the technology and the publication of updated standards to ensure installation consistency and quality.
What are the regulations?
Changes included in approved document Part B of the Building Regulations, which came into effect in April 2007, made inclusion of domestic sprinklers acceptable in certain conditions. Design and installation must be in accordance with BS 9251: 2005. Futhermore, the approved document guidance states that they may be used as a whole building measure or for only part of a building.
How do sprinklers work?
Small covered nozzles about 100mm in diameter are the most common type of sprinkler and usually one per room is the only visual evidence of the system’s existence. They are fed from a central water supply.
The sprinkler heads need to be positioned for best effect and be able to deliver adequate coverage to the rooms served. The sensor is either a glass bulb or a fusible link designed to ensure reliability and set to trigger at between 68 and 79ÞC for the average installation.
Sprinkler heads, sensors and pipework have now been engineered with domestic systems in mind rather than just downsizing commercial fittings. That means they are small enough to be incorporated into a home, but robust enough to do the job.
Usually CPVC pipework, which is non-corrosive, is used. This is an engineered thermoplastic and has a proven track record for these kind of applications. Jointing is by cold solvent welding, which again is ideal for domestic installations where ability to install the system without significant disruption or surface mounting is important.
Systems can be fed from the mains where supply is reliable and the pressure constant. Where this is not the case a tank and pump are required to deliver an equivalent supply. Systems should be designed to deliver 60 litres/s for 10 to 30 minutes depending on the room size and complexity of the accommodation.
Advances in technology mean that fears over false alarms or accidental activation can be put aside and, compared to a response by the fire brigade, the quantity of water involved is a tiny fraction.
However, if pipework is routed through ceiling voids and corridors it is important that it is frost-protected. Maintenance must also be regular and undertaken by professionals. Ensuring this is done in the domestic arena is probably the weak point in the case for sprinklers.
What’s the benefit?
Sprinklers are most commonly used to protect longer-than-normal escape routes. However, they are also useful in loft conversions where the property is three or more storeys, in situations where there is little or no compartmentation in the intermediate floors or where there is an open-plan arrangement with no doors or compartmentation to stairs (see picture). They are also used where full fire brigade access may not be available.
One of the biggest attractions is in enabling more flexible layouts and the opportunity to create large open areas with few restrictions such as fire doors or partitions.
In the case of a house of four storeys or more a sprinkler installation is regarded as an alternative means of escape.
Using sprinklers can also be more economic and practical than specifying conventional fire protection. There is a significant reduction is compartment construction, fire doors and fire sealing that can offset the cost of the sprinklers.
Usually the labour involved in the sprinkler installation is also considerably less. However, they should always be designed and installed by competent professionals and must be commissioned and signed off as part of the Building Control approval.
The idea of domestic sprinklers is still relatively new to the UK and there is a general lack of guidance. The British Fire Sprinkler Association (BFSA) produces good-practice guides and a source of contacts. Its technical guidance note 1 is a good place to start with information. This sets out clear advice for the design installation and commissioning of a system.
Building control officers are required to make a judgment on the applicability of the system being proposed and its relative value. However, there is very little official guidance to set the ground rules apart from the British Standard and the trade guidance. This can lead to inconsistency and confusion between various schemes. What may be accepted by one building control officer may not be accepted by another. This, of course, is not unique to sprinkler design, but few are willing to risk fire safety as a point for debate.
Hopefully clear guidance will be available shortly to complement the existing documents and ensure that full advantage can be taken of this valuable technique.
It offers a great advantage to designers without compromise to safety.