Fire rating- where 30 and 60 don’t equal 90
It is estimated that around 70% of UK build installations feature 30 minute ceiling types. However some lighting manufacturers are producing and promoting downlights that have only been tested at 90 minutes, while claiming that they are fully compliant with 30, 60 and 90 minute ceiling constructions. Each ceiling is rated separately for a reason, and in fact say JCC Lighting, the test for 30 minutes is what your customers should really be looking out for in most domestic installations.
There is still a lot of confusion within the UK building industry over the building regulations. Often the problem of deciding which lights should be fitted in order to comply with Part B ends up with the contractor at the point of installation, whereas that decision should only be made during the design process in respect of the type of ceiling involved.
In some cases, it has almost become the norm to fit a downlight tested for a 90 minute ceiling in a 30 or 60 minute ceiling. But here lies the risk.
WHAT DO THE CEILING RATINGS MEAN?
Ceilings have to be constructed to provide protection to the floors above and also to adjacent buildings for a duration that is specified in Part B, which is a standard put in place to ensure that a building’s structure provides adequate protection to personnel in the event of a fire and during emergency evacuation.
Different types of building require a specific method of ceiling construction. Each ceiling construction uses different materials and has joists spaced at different widths. At 90 minutes the joist widths are at 450mm and utilise two layers of 15mm gypsum board impregnated with strengthening fibres. The ceiling will fail under duress when the moisture is evaporated by the heat of the fire and the board collapses under its own weight (and that of the downlight). At 550mm joist spacings used in 60 minute ceilings the weight is supported over a greater distance and thus will collapse at an earlier stage.
Couple to this the fact that the 60 minute gypsum board is not impregnated with fibres to hold it together and it is easy to understand the differences and associated risks.
The level of resistance is proportional to the risk involved and the location of adjacent dwellings. 90 minute fire rated floors are generally only required in extreme construction, such as tall buildings or towers. 60 minute fire rated floors are used in between shops and flats, and multiple occupancy buildings, while 30 minute fire rated floors are the most common, used in 2-storey houses (detached or terraced), flats and maisonettes.
Right now there are products on the market which only comply in a 90 minute ceiling, which is rarely required, but this is no guarantee that they are suitable for 30 and 60 minute ceilings as these are a less robust construction.
Developments in building materials also mean that it is imperative to use fully tested downlights. Timber I-joist systems are becoming increasingly popular as an alternative to solid beam ceiling constructions. As they are manufactured from laminating layers of wood together, they are lighter and easier to manoeuvre, together with the benefit of being able to span greater widths without undue flex in the floor system.
However, as these joists are thinner, they are less resistant to the passage of fire. This again means that any downlights installed must also be tested for I-joists as well as solid beam constructions.
FIREHOODS
The issues with fire-rated downlights go beyond that of rigorous testing. Most lamp sources need to disperse heat and require a certain amount of ventilation, which can therefore compromise the ceiling. The construction of the downlight needs to ensure that there is enough ventilation to keep the lamp cool, while having the ability to seal the fitting against fire.
The subject of fire-rated downlights and hoods is a complicated one. As heat is always going to be present with any lamp source, fire safety and liability are of obvious concern.
Providing the fire-rated downlight is acquired from a reputable manufacturer and has been fitted correctly should be reassurance enough that the fixture is doing its job correctly.
However, it is difficult to see whether a firehood has been fitted correctly, as any disruption to the hood could compromise the safety it is claiming to offer.
Building regulations place a considerable amount of restraint on modern developments and while a limited amount of downlights meet all the required regulations including Part C, which requires special seals to inhibit the flow of air and moisture, and Part L relating to energy efficiency, firehoods don’t provide a seal. This means that when used with a standard downlight, it doesn’t meet the regulations and wouldn’t offer any protection in the upper floors of modern houses. This type of fitting would only be useful when installed on the ground floor of a property.
As house building and developments becomes more technical it will become increasingly difficult to ensure total fire safety. The use of hoods will be limited due to space restrictions, and testing will be paramount to ensure protection against fire.
LAMPS
With so many different lamp types available now, lamp replacement can also be an issue as this is where problems can occur if people use the wrong lamp type. As far as firerated products are concerned, the issue of aluminium and dichroic lamps can be a concern, as some people don’t know the difference. Due to issues with backward heat dissipation in dichroic lamps, aluminium reflector lamps are essential for use in fire-rated products as they send the majority of the heat forwards through the front of the fitting.
However, as lamp manufacturers are reducing the number of dichroic lamps produced while increasing the production of aluminium lamps, this risk is gradually reducing.
The lighting industry is starting to provide the solution by producing dedicated lamp bases so that the wrong type of lamp cannot be fitted, therefore reducing any risk of using a dichroic lamp. In line with the latest legislation a variety of dedicated lamp holders are now evolving that will only accept specific low energy lamps, and eventually these will replace the traditional lamp base. It is still possible, however, to install an incandescent or CFL into an existing BC or ES lamp base, but in order to fully comply with Part L specifications, the new standard calls for a dedicated low energy lamp and socket combination
WHAT NEXT FOR FIRE RATED SOLUTIONS?
Getting the testing message across to house builders, developers and contractors isn’t always easy. Although some of the national house building companies are concerned about fire safety, many see it as an issue for the building contractor. Even architects’ plans don’t necessarily go as far as specifying a particular downlight fitting. This means the building contractor doesn’t have any guidelines to follow when matching firerated products to ceiling types.
Manufacturers will be increasingly challenged to meet all building regulations and testing procedures to ensure maximum fire safety.
Contractors need to fully understand the risks and have an understanding of the building regulations and the testing process, and use this knowledge in all domestic and commercial applications to minimise risks. It will also be increasingly important for the house owner to have an understanding of the requirements, to ensure they are fully compliant with their existing fittings and to protect their home from fire risks.
At JCC we believe the message needs to be clear - when you are fitting downlights you must ensure they are tested for the ceiling construction.
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