9 5月 2018
Gary Strong looks at the value of automatic fire suppression systems, in an article based on a recent submission to the London Assembly consultation on installing or retrofitting sprinklers in all buildings.
Buildings with automatic fire suppression systems (AFSS) installed, particularly residential buildings, have a number of advantages over those without such systems.
An AFSS such as a sprinkler installation is designed to control and extinguish a fire, without human intervention, soon after it breaks out. It plays no role in fire prevention and should not be seen as a panacea in terms of safety; instead, it should be considered alongside other systems and processes of fire control and building evacuation.
Sprinklers are designed to extinguish small fires to prevent them from escalating, thus protecting the building structure but not generally the contents. As sprinklers dispense water, which is not recommended for suppressing electrical, oil or grease fires, they should not normally be fitted in kitchens, where such fires are likely to occur.
Sprinklers can also be detrimental to the contents of a building such as a warehouse that contains high-value electrical goods, and to certain IT installations. In dwellings, sprinklers should not be placed above cookers because the heat may trigger them. Sprinklers are also often installed in electrical rooms – in dwellings as well as commercial or industrial premises – where an alternative suppression system may be more appropriate.
If the building has been designed and maintained correctly, fire resistance will normally last a minimum of 30 minutes but could be longer, which would allow enough time for the sprinklers to restrict the blaze to its source.
However, it should be appreciated that once a sprinkler head has been activated and extinguished a fire, it will continue to discharge water until it has been manually turned off, unless fed by tanked water reserves. This is likely to result in water damage to contents, for which residential tenants often do not have appropriate insurance. The same will occur if the sprinkler head is activated by misuse or vandalism. However, it should be borne in mind that, without sprinklers, firefighters may cause much worse water damage.
There is anecdotal evidence from the fire and rescue services and from RICS members who have inspected buildings after fires that sprinklers fitted in individual apartments can contain fires within those apartments and prevent them spreading to the rest of the building.
In the context of recent major fires, there is a need for a thorough assessment of all available data and, if necessary, to conduct new research on the effectiveness of sprinklers in all types of building.
Sprinklers in an apartment will not stop fire spreading via the outside of a building fitted with combustible cladding or window frames – the latter potentially compromising compartmentation and fire separation of flats as much as the former. Sprinklers could be effective in stopping the external spread of a fire that starts internally, but this will not mitigate against combustible cladding, which could ignite, for instance, if exposed to an external fire.
While having sprinklers installed may not significantly reduce the risk to lives, which may already be very low thanks to other fire-engineered measures, they will limit smoke and thus enhance life safety, as well as preserving the building.
There is anecdotal evidence that there may be an advantage in terms of lower insurance premiums as well, because insurers are likely to see less fire risk in a building fitted with AFSS and thus reduce rates. RICS invites members who have direct experience of such lower premiums to email Alan Cripps.
According to the National Fire Chiefs Council, when sprinkler systems have been in operation:
Since the Grenfell Tower fire in particular, there is also a perception among the public, including building occupiers and investors, that a building fitted with AFSS is safer and therefore more likely to be acceptable to residents, owners and investors. There is anecdotal evidence that some banks are already looking at whether or not to lend on high-rise and high-risk buildings without AFSS. The RIBA has also called for sprinklers or AFSS to be mandated in all new and newly converted residential buildings, as is the requirement under the Building Regulations in Wales.
There are some groups of people who are particularly likely to benefit from the cost of installing AFSS, especially those with reduced mobility who cannot exit a building quickly in the event of a fire – where a simultaneous evacuation policy does exist. In residential premises, it is generally assumed that most occupiers’ mobility is not impaired, although each property must be individually assessed.
Investors and owners of buildings or apartments with AFSS fitted may also benefit from a more sustainable valuation of their assets, as buildings without systems – particularly high-rise, higher-risk buildings – may in time be less well valued due to less market demand.
Sprinklers are mandatory in many multi-storey commercial buildings, which are arguably a lower-risk category than multi-storey residential buildings, because occupants are generally awake and they are likely to have better fire safety management systems.
The cost of providing AFSS in a residential building will vary considerably, and depends on the design, layout, height and construction of the building. There is usually a general cost for the infrastructure, and this can be significant if tanks and pumps and a room to house them are required, as well as a cost per sprinkler head that will depend on the number of apartments and the number of rooms in each.
Other factors affecting the cost include the following:
The cost-effectiveness of AFSS generally increases with the size of the building. The British Automatic Fire Sprinkler Association (BAFSA) produces guidance on costs generally, which is regarded as an excellent source of reference.
RICS itself provides an indicative range of benchmark costs, detailed below, for which it has been assumed that the entire building will have sprinkler protection in the form of a dedicated system, and that individual apartments will be fitted to a sprinkler head density of one every 10 sq. m. It has also been assumed that the building will be larger than 10,000 sq. m. For smaller buildings, the cost per square metre will increase one head per 10 sq. m is very dense, and one per 20 sq. m may be appropriate where the risk is lower; see CIBSE Guide E.
Please note that these costs are net of VAT but inclusive of main contractor preliminaries, overheads, profit and installation. They are indicative only, and must not be relied on for individual buildings, which will require a full survey and a cost plan to be produced.
Installed AFSS include both sprinkler systems and misting systems, so costs could also vary according to the type used. While misting systems are at present more expensive, they use less water and so require less storage space, as well as causing less damage.
The current standards allow misting for buildings up to 30m in height, under BS 9991, or 45m in height, the installation standard to which BS 9991 refers, and this contradiction needs to be resolved. CIBSE has noted that Marriott Hotels allow mist to National Fire Protection Association standards in all buildings.
There are a number of factors that must be considered to justify installing AFSS in existing residential buildings.
RICS would generally only consider retrofitting to be necessary in higher-risk residential buildings where:
However, the RIBA has recommended the retrofitting of sprinkler systems to all existing residential buildings that are more than 18m in height, arguing that this could be reinforced by a requirement for such systems as a “consequential improvement” where there are “material alterations” being made to existing high-rise residences.
RICS does not generally consider retrofitting AFSS to low-rise, lower-risk residential buildings to be necessary or desirable, unless a survey or fire-risk assessment determines otherwise. For more information on this issue, refer to BAFSA’s report on retrofit sprinkler installation and the Building Research Establishment’s report on the effectiveness of sprinklers in residential premises.
The cost of retrofitting an existing residential flat with a sprinkler system will depend greatly on the building design, layout, number of rooms, type of construction and height, as well as the availability of adequate water pressure and storage space. As a result, no typical cost is available.
RICS recommends that generalisations on costs are not assumed, and that every building is assessed individually, as mentioned above. The BAFSA report does, however, provide case-study costs for retrofitting sprinklers to an existing residential apartment.
The main factors affecting the feasibility of retrofitting existing buildings with AFSS include:
As a result of the Grenfell Tower fire tragedy, media attention has been drawn to the advantages of AFSS. Such systems are likely to be demanded increasingly by tenants even though, on the whole, they have very little knowledge of systems, of the cost of installation or maintenance, and of who will pay.
AFSS play an important role in helping to save lives and protect buildings, but there is a general perception that they could be a panacea. AFSS should always be considered in the context of an overall fire safety risk assessment plan.
It is essential to avoid mitigating one risk – fire – by increasing another – for example, legionella – so all work should be undertaken by professionally qualified persons who are competent in the disciplines required. The legionella risk may increase as piping “dead legs” are introduced into the domestic water system, but good design and system management can minimise the risk
This article first appeared in RICS Building Surveying Journal (May/June 2018)