Project focus: Crown Place, Cardiff

Once a commercial office building, Crown Place, situated in the heart of Wales’ capital city, just 100m from Cardiff University, was converted into a £13 million student accommodation property in 2018.

The architectural practice AWW was tasked with the redevelopment of the 1960s building, which accommodates 378 students in a range of studio, one- and two-bedroom apartments, over seven storeys. The project also included communal student spaces, including a gym, cinema, as well as individual and group study rooms, in addition to external private amenity space.

Burning issue

Surprisingly, the original design for Crown Place did not include a fire sprinkler system. However, following the Grenfell Tower fire in June 2017, it was decided by the design team – which comprised Crown Student Living, AWW, F P Hurley and Sons, and the Local Authority Building Control Officer – that it would be beneficial to add a fire suppression system to the building.

“The difficulty we faced was that the building and services had already been designed and no space had been allowed for a traditional sprinkler system,” explains Marc Davies, senior project manager at F P Hurley and Sons (M&E sub-contractor).

Following some research it was proposed that a misting system was to be installed, accredited to BS8458.

“As a provider of accommodation for students, it is vital to meet the appropriate building regulations in regard to fire safety,” says Eddie Sibley, CPD manager at iMist, the company that designed and installed the fire suppression system. “There are many instances in which a fire can start, especially when housing a high volume of people.

“Candles, cooking appliances, incense and electrical goods are used excessively by students and increase the chances of a fire starting in the premises. Effective fire suppression installed into the student accommodation will prevent the spreading of any fires in the property and will keep the residents safe.”

High spec

The system design features a dual pump set located on each floor that serves the misting system and a separate pump to serve the communal area. Each pump set requires a dedicated water supply capable of providing a minimum of 24Lpm at 3 bar.

“I-Mist STX12 systems are an effective form of fire suppression working at a nominal pressure of 100 bar,” explains Davies. “The pressure, in combination with calibrated discharge nozzles, produces extremely small droplets which make fire suppressing extremely effective.”

The main components of the system include:

  • an electrically operated pump unit, located in a riser cupboard on each floor;
  • a water supply filtration system to prevent dirt entering the system, which could potentially block the nozzles;
  • inlet and outlet isolation valves, which can be used for servicing the pumps and to isolate the system in an emergency;
  • audible and visual discharge indicator alarm that would sound on the unit if system is activated;
  • volt-free contacts for remote monitoring which go back to the building monitoring system. The building management system is set up with critical alarms, such as the iMist system, which activate a sounder in reception.

Set up

A fire suppression system acts to provide a rapid fire fighting response in the event of a fire incident, automatically responding with a water attack prior to the fire brigade’s arrival to safely evacuate the building’s occupants.

The system is activated by fire temperature alone, not smoke or burnt cooking. The closed frangible bulb-type nozzles are activated once the temperature rating of the nozzle bulb exceeds 57°C.

“The system is designed as a wet pipe system and so the pipe is normally charged with water at low pressure,” explains Davies. “In the event of a nozzle operating, the flow is monitored and, after a short delay, the pump started. Water is discharged as mist through the open nozzle. More nozzles may operate over time depending on the fire size and location, until the maximum capacity of the system is reached.”

A single iMist nozzle uses a maximum of 8 litres of water per minute, compared with in excess of 50 litres per minute from a traditional sprinkler system. The pump outputs at 100 bar and requires only 1 bar incoming water pressure.

Fire protection systems are easy to install, cost-effective and discreet. The nozzles have been designed to disappear into the ceiling landscape, only protruding 2cm. The aluminium nozzles are available in a range of colours to compliment or blend into their surroundings.

“We use high-quality flexible hoses with a stainless steel braiding and hydraulic fittings for our fire suppression system, which leads to a quick and smooth installation process,” explains Sibley. “Large volume installations are typically three times faster than an equivalent sprinkler system, even in the most challenging historical properties.”

Rapid response

The purpose of these water mist systems is to provide a form of defence prior to arrival of the fire brigade, with iMist claiming a 100% success rate in suppressing live fires.

“The excellent fire suppression ability of fine water mist has been recognised for many years,” says Sibley. “This performance is due to the large total surface area of the droplets combined with the high speed at which they convert to steam, thus absorbing the energy of the fire. The average water fog droplet has a total surface area at least 100 times greater than that obtained by a conventional sprinkler system for the same volume of water.

“Having extinguished a fire, water mist will continue to cool the source, preventing reignition, and at the same time dramatically reducing the harmful products of combustion. By atomising the water into a fine mist, the droplets immediately convert to steam and absorb the energy, quickly suppressing and controlling the fire. Once the fire has been suppressed the droplets being discharged continue the effect by removing heat from the fuel source (i.e. liquid fuel, oil, plastics, fabrics, wood, cable and paper), thus preventing reignition. Additionally, this leads to a localised reduction in oxygen from the flame front, which creates a local inert atmosphere as it starves the combusting fuel of oxygen.”

All fire safety equipment requires an annual service and iMist services Crown Place every year to ensure the pumps are working efficiently, software updates are installed and nozzles are free from obstruction.

Appealing alternative

There are numerous benefits to installing a fire suppression system in addition to protecting lives. As these systems react rapidly after a fire breaks out, they offer protection to the property and as minimal water is used it also reduces post-fire refurbishment costs. There is also no need for a water supply tank, which saves space and installation time.

Although water mist systems have been used in the UK since the 1940s, they remain a fairly new concept in the market. However, they are gradually becoming better known by homeowners and property developers who are attracted to the benefits when compared to fire suppression alternatives.

The Grenfell Tower tragedy has undoubtedly served to highlight the inadequacies in fire safety regulation, but fire services and many other organisations have been lobbying for updates in fire safety regulations long before this incident.

“The need, demand and mandatory requirement for fire suppression systems continues to grow,” says Sibley. “It will, almost certainly, be a mandatory requirement across the UK sooner rather than later. As people become more aware that large amounts of water are not required to suppress fire, mist fire suppression systems are becoming the go-to option for these types of development.”

When is a fire suppression system legally required?

BSI 9991 says you must have an Automatic Water Fire Suppression System (AWFSS) in the following circumstances:

  • Multi-basement buildings.
  • Dwelling houses with one or more storey greater than 7.5m in height (four storeys).
  • Internal planning of flats and maisonettes.
  • Open plan layouts.
  • Provision of inner rooms in flats not more than 4.5m in height.
  • Extended travel distances within an open-plan flat.
  • Flats where occupants are not capable of independent evacuation.

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