Fire rated downlights are made from or contain intumescent material, this material expands when it reaches a certain temperature sealing off the hole and slowing down the spread of fire. The fire is then unable to have direct access to the structure of the building.
Fire rated downlights are used to maintain the ceilings fire integrity. Part B of the Building Regulations covers fire safety and has been a legal requirement since 1987. Not all downlights have to be fire rated but it is important to know when and where they should be used.
When a recessed downlight is installed, a hole must be cut into the ceiling to allow the downlight to be mounted in. This hole reduces the fire integrity of the ceiling. In the event of a fire, flames spread through the holes and set light to the structure of the building. Most ceilings are constructed from timber joists which in the event of a fire, could burn and collapse in a matter of minutes. If the structure of the building is made from materials with higher temperature ratings such as concrete then fire rated downlights are not necessary.
The minimum fire rating for downlights is 30 minutes; this rating is for ceiling joists with a spacing of 600mm. This should allow enough time for the occupants to escape the building or for the fire service to extinguish the fire without floor or the entire building collapsing.
There are three types of structurally different ceilings:
1. 30 minute ceilings have ceiling joists with a spacing of 600mm and with one layer of 12.5mm plasterboard fixed to the underside of the joist.
2. 60 minute ceilings have ceiling joists with a spacing of 600mm and with a double layer of 15mm plasterboard fixed to the underside of the joist.
3. 90 minute ceilings have ceiling joists with a spacing of 450mm and with a double layer of 15mm plasterboard fixed to the underside of the joist.
Most fire rated downlights are suitable for all three types of ceilings but some are not and only rated for 30 or 60 minute ceilings.
When downlights are being installed in upper floor ceilings with roof space only above them they don't necessarily need to be fire rated. This is because there is little risk of the fire spreading through the holes and onto the structure of the building. However, fire rated downlights have many other advantages. They are also approved to other important Building Regulations such as Part C - moisture protection, Part E - acoustic resistance.
Building Regulations now state that a room should be air tight, if you have multiple downlights that are not fire rated warm air will escape through the holes. In cold ceiling spaces such as loft areas, downlights act as chimneys and draw out the warm air from a room.
Even if you feel that fire rated downlights are not important for preventing the spread of fire then these other Building Regulations should be considered. Most adjustable downlights do not provide moisture protection or acoustic resistance.
To summarise, although fire rated downlights are slightly more expensive, they are safer, comply with the Building Regulations and may offer peace of mind.