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Building Services Engineers always seem to draw the short straw when it comes to the design of residential apartments. Developers and architects want beautiful, novel and perfectly illuminated apartments, yet they also want as many apartments as possible in the smallest area – and never want to provide space for service risers.

We are never going to abolish service space altogether, but at least we now have a chance to use those risers to provide a considerable boost to the sellable qualities of an apartment by using residential sprinklers. Providing a residential sprinkler system in a building may not sound particularly heroic or a proposition likely to endear you to the designers. However, when the role of sprinklers is reviewed we can see the considerable benefits to be gained.

In the UK all residential buildings are required to comply with the functional requirements of the Building Regulations, usually by applying the recommendations of Approved Document B¹ or other relevant guidance documents. Other methods of complying with the Regulations are acceptable, although the burden of proof is on the design team.

In comparison the United States has various model design codes including the International Building Code, (IBC), the National Building Code, (NBC), the Standard Building Code, (SBC), the Uniform Building Code, (UBC), and the National Fire Protection Association, (NFPA), Life Safety Code. To add further complexity, each state has its own building legislation. This is based on one, although sometimes more, of the standard models and can have subtle local differences.

Despite some differences in the evacuation of the occupants of residential apartments, it is possible to give a comparison of the internal layouts of UK and US residential designs. In this case it is proposed to use the NFPA Life Safety Code² and to compare it with the requirements of Approved Document B.

In the UK there are three different internal flat layouts recommended by the Approved Document, these are:

• Protected entrance hall approach – all habitable rooms, (not the kitchen and bathrooms), should be accessed via a 30-minute fire rated protected corridor. The maximum travel distance from the door of each habitable room to the flat entrance door along this protected corridor should be no greater than 9 m. There are no limitations on the size or distance in each of the habitable rooms.
• Open plan design – the flat should have a travel distance of no greater than 9 m from the furthest point in the flat to the entrance door. This is normally only used in studio flats or crash pads.
• Alternative means of escape – the kitchen and living accommodation should be separated from the bedrooms by a 30 minute wall. Two means of escape should be provided from the apartment, one from the bedroom portion and the other from the living room/kitchen.

The majority of the apartments in the UK are typically designed in accordance with the protected entrance hall method, with a smaller number constructed as open plan apartments. The alternative exit approach is not generally used due to the inherent design limitations.

The overall problem with these typical layouts, identified by designers and developers, is that it restricts the flexibility of the space. Occupiers want large open plan accommodation that generates a feeling of space from the moment they open the apartment door. On the other hand developers want to make the maximum use of the apartment’s usable space.

The ideal solution is to design the apartment so that access is possible from the entrance door immediately into the living room and kitchen space, with bedrooms and other accommodation located remote from the flat entrance door. A typical example of this proposed layout is shown in architect Broadway Malyan’s sketch drawing (figure 1).

The problem with this proposal is that it doesn’t follow the typical internal layouts given in Approved Document B and has enclosed inner bedrooms, (bedrooms accessed from the living room), provided without an alternative means of escape. This proposal is unlikely to be accepted by the statutory authorities.

Approved Document B recommends the way of overcoming these shortcomings is to either provide an alternative means of escape from the bedrooms or to remove the inner room situation by opening the bedrooms to living room and to plan the space so that the maximum travel distance to the furthest point in the apartment is limited to 9 m. This would meet the typical layout given in Approved Document B. Neither option is generally acceptable to a developer, due to the additional impact of providing an alternative escape route, (both in cost and space terms), or the limits to the apartment layout by providing bedrooms open to the living space with only a 9 m maximum travel distance.

Anyone familiar with American sitcoms or holiday home reality tv shows will have seen wonderful large American apartments with bedrooms located off the huge open plan living room. How do they do it?

The answer is the provision of residential sprinkler systems. The NFPA Life Safety Code places the emphasis on the provision of active protection systems. These determine the restrictions on the internal layout of the apartment and almost all new apartment buildings are required under the NFPA code to be provided with residential sprinkler system.

Where sprinklers are not provided in an apartment the NFPA code takes a similar stance to the guidance of Approved Document B in recommending that alternative means of escape be provided from all inner rooms, (including the living room). Where a sprinkler system is provided the only fundamental limitation on the layout of a single level apartment is that the travel distance from the furthest portion of the flat to the flat entrance door should not exceed 38 m. The NFPA code permits the use of inner bedrooms without a requirement to provide an alternative means of escape from the rooms and the increased travel distance for the open plan apartment is, at 38 m, far greater than the maximum distance of 9 m permitted in Approved Document B.

Approved Document B does not consider the advantages gained by providing a residential sprinkler system. It does however recognise that the guidance relating to the layout and planning of apartments consists of recommendations and alternative solutions can be provided to satisfy the functional requirements of the Building Regulations.

One alternative is to use the recommendations contained in an appropriate code of practice. In this case the statutory authorities may accept the recommendations contained in the NFPA Life Safety Code as meeting the functional requirements of the UK Building Regulations when sensibly applied.

Therefore, if the developer or design team requires an open-plan layout for a large apartment, one of the safest and most appropriate methods of achieving this is to provide residential sprinklers.

Reducing fire resistance

Following the guidance of Approved Document B, it is necessary to provide fire resistance to all elements of structure. It is also necessary to horizontally and vertically separate each apartment from the common corridor and adjacent apartments by fire resisting construction. The fire rating of this construction varies as a function of the buildings height. Approved Document B recommends that the building be constructed of 90 minutes fire resistance when it is over 18 m but less than 30 m in height and 120 minutes fire resistance when the building is higher than 30 m.

The impact of providing 90 minutes or 120 minutes fire resistance to both the elements of structure and all compartment walls and floors can have a major commercial implication. The provision of sprinklers to residential apartments could be used in conjunction with time-temperature analysis and other fire engineering calculation tools to potentially reduce the level of fire resisting construction and therefore reduce the cost of the system.

It is generally shown that where sprinklers are installed the period of fire resistance can usually be reduced by a minimum of 30 minutes. Given that residential sprinklers are generally estimated as costing up to 1·5% of the total building cost³ a cost benefit analysis can be undertaken to determine the potential savings for the scheme.

Sprinklers are not only a useful tool for maximising the spatial layout of the apartment and potentially reducing the periods of fire resistance. They can also reduce fire fatalities and injury. Approximately 80% of all fire deaths occur in residential properties; therefore any reduction in residential fire deaths will have a substantial impact on life safety.

In 1998 Vancouver, a city of almost 550 000 inhabitants, did not have a single fire fatality. This impressive statistic is accredited by Vancouver’s fire chief Ray Holdgate⁴ as being a direct result of a 1990 by-law requiring all new residential construction to be provided with sprinklers. This law had a major impact on building design with almost 38% of all multi-residential units in the City being provided with a residential sprinkler system by 1999.

Similar statistics are recorded for other towns in the US. In 1986 Scottsdale, Arizona passed local legislation requiring all buildings to be provided with sprinklers, including domestic properties. The result is that 50% of all residential buildings, (a total of 41 408 properties), are now provided with sprinklers. Between 1986 and 2001 there were no fire deaths in residential properties provided with residential sprinklers but at the same time 13 fire fatalities were recorded in properties without sprinkler protection.

Other US areas that have enacted residential sprinkler laws also report a similar reduction in residential fire deaths. While residential sprinklers are not in widespread use in the UK anecdotal evidence is showing that these systems have already prevented serious fires that may otherwise have potentially cost lives. This goes to show that generally the provision of sprinklers has a major impact on saving lives in residential developments.

Accidental discharge

Many developers are concerned about the risk of accidental discharge of the sprinkler system in their apartments and the risk of being sued by the occupiers for the damage caused.

Despite the popular belief of Hollywood movie-makers, you will not be woken in your bed by a cold shower if the sprinklers in an apartment in your building operate (even in your own apartment). Sprinklers should be considered in a similar manner to showerheads. They are individually activated and therefore only the sprinklers immediately adjacent to the fire will operate.

This reduces water damage by controlling the spray to only those areas affected by the fire. In the majority of instances the spray will produce far less water damage than if the fire service attend the scene. Indeed the report into the impact of sprinklers in Scottsdale, Arizona highlighted that 1290 litres were used by sprinklers in a fire while when sprinklers were not provided the fire service used on average a total of 11 110 litres per fire.

Another concern is that by providing sprinklers in an apartment the occupants will not be able to use candles or other open heat sources for fear of activating the sprinkler system. This is incorrect, as the correct rating of the head, whether it is a fusible link or glass bulb, would ensure that this would not occur.

The other concern from developers is about accidental discharge due to breakage of the bulb by the occupants. Unlike a normal sprinkler head that comprises of an open glass bulb, residential sprinkler heads generally comprise of a recessed glass bulb hidden inside the ceiling or wall cavity. It is not possible to accidentally knock the bulb as it is located in a recess, safe from balls and other projectiles.

The recess in which the bulb is located is covered with a flat metal plate. This plate is soldered onto the sprinkler head fittings and requires considerable force with a sharp object, or activation via direct application with a naked flame to release. This is far less likely to occur than other sources of water damage, such as an overflowing sink or bath.

In the event of discharge, (due to a fire), when the apartment is unoccupied, it is possible to link the sprinkler valve set to a remote monitoring service to alert the fire service. This is a definite improvement over an unsprinklered apartment where the fire would continue to burn until the smoke was noticed by a neighbour or passer-by.

The report highlighting the impact of providing 10 years of residential sprinklers in Scottsdale Arizona⁵ calculated that the level of water damage is minimal in comparison to an unsprinklered fire. The Scottsdale authorities also calculated that provision of sprinklers reduced the cost of fire incident damage from US$45,000 dollars for an unsprinklered building to US$2,166 where sprinklers are provided.This is an enormous reduction in costs resulting from a fire incident and shows how residential sprinklers both prevent fire losses as well as minimising water damage in a property.

It is possible for any system in a building to go wrong in such a manner that a small amount of disruption will occur. However, in the case of sprinklers, considerable effort has been made to ensure the risk is minimised. In fact the sprinkler community generally rate the chances of accidental discharge for any sprinkler systems as being in the region of 1 in 16 million!

Rather than provide a drab, unattractive apartment with a large amount of space wasted on the provision of a protected entrance hall serving all the habitable rooms, or, alternatively, limiting the size of the apartment so that the purchaser would be hard pressed to swing a cat, the use of sprinklers can increase the apartment’s openness and feeling of space.

Removing the requirement for a protected entrance hall and allowing bedrooms to be accessed directly from the living space will create this increase in openness. The apartment’s increased spaciousness will have a dramatic impact on desirability and therefore value.

The use of sprinklers may also reduce the required period of fire resisting construction. This can reduce construction costs, increasing the profitability of the building.

However by far the most important issue is that sprinklers have a proven track record of dramatically reducing the risk of fire fatalities and serious injury throughout the World and if installed in the building would significantly decrease the risk of a serious fire.

Gary Daniels is a senior fire engineer for Hoare Lea Fire Engineering.

References
¹ Approved Document B to the Building Regulations. 1991 (2000 edition), HMSO.
² R Cote (editor). ‘NFPA 101: Life safety code’, National Fire Protection Association, 2000.
³ Paul Peg. Home Fire Sprinkler Coalition. www.homefiresprinkler.org
⁴ R Holdgate. ‘Mandate for sprinklers’, Fire Prevention – Fire Engineers Journal, September 2001.
⁵ Jim Ford. ‘Automatic sprinklers; A 10-year study. A detailed history of the effects of the automatic sprinkler code in Scottsdale, Arizona’, 1997.