Downlighters to dwelling houses Subject No: 9 Subject: Downlighter & Recessed Light Fittings Introducing Officer: D Potter (WDDC) Date: 13/10/1998 Downlighters are becoming increasingly widespread with the domestic new build and refurbishment sector. Not only do they provide a light source but also by being recessed in the ceiling, unsightly light fittings are avoided. However, it is the position within the ceiling voids, which can lead to several possible problems occurring. Namely, a reduction in the fire resistance of any ceiling if applicable since the size of any hole can be up to 140mm. Also a build-up of heat due to the confined area within the floor void in which these are invariably fitted: causing, at worst, the surrounding floor joists to scorch, smoulder and in extreme cases, ignite. Having identified two major concerns regarding the use of downlighters; can their use be accepted under Building Regulations in terms of fire safety? Building Regulations B3 Internal Fire Spread (Structure) stipulates a fire resistance of 30 minutes for a domestic upper floor in a two-storey dwelling. This is further refined by including references to 3 criteria. Namely:- Loadbearing capacity (30 minutes from underside)   Integrity (15 minutes from underside)   Insulation (15 minutes from underside) Recent full scale fire tests undertaken by a proprietary fire protection company reveal that in cases where downlighters are installed and a fire occurs within the room, smoke spread into the floor void via a downlighter will be almost immediate. The fire load within the room may determine the smoke temperature, which at first ignition may be low but will quickly rise to above 500 degrees. Obviously, since the downlighter has breached the ceiling, the smoke will filter quite rapidly into the void and may eventually cause ignition of the surrounding floor joists. However, the question remains, will the floor joist adequately support the floor for the 30 minute period? Whilst the integrity and insulation of the downlighters being of plastic or metal construction will not generally achieve 15 minutes, will their positioning affect life safety – especially means of escape? Again fire tests indicate that after 15 minutes, some areas of ceiling are already to failure. Having identified the potential problems, can their use be accepted under Building Regulations without providing a secondary form of fore resistance? In general, normal 240v recessed downlighters (normally about 140mm in diameter) have not been found to be problematical where there use is restricted to 3 or 4 units placed a reasonable distance apart. But, a potential problem has been uncovered with regard to low voltage lighting. RECOMMENDATIONS for standard 240v downlights 1 Where installed on a ground floor ceiling of a 2 storey house, a maximum of 4 units can be provided at a minimum of 1.2m centres, fixed centrally between floor joists without fire resistant units or covers. 2 Where installed within the first floor ceiling of a two-storey house, the insulation is pulled back to allow ventilation. 3 Any other circumstances fire resistant units or covers are to be provided. Low Voltage Lighting This form of recessed lighting generally takes the form of small diameter units with an average 82mm hole, a halogen bulb of up to 50 watts and a transformer with thermal cutout. The operating temperature of the unit can be in the region of 400 degrees. There have been several recent cases where this form of installation has caused damage to property. In general, although no major property damage occurred, adjacent floor joists were charred, but not sufficiently to require replacing. After having discussed the above indents with Stn O Harmer, Dorset Fire and Rescue Service, I would suggest the following recommendations are adopted by the Dorset Technical Group. RECOMMENDATIONS for low Voltage Lighting (non FR rated) 1 Where installed on a ground floor ceiling with first floor above the unit should be surrounded by 12.5mm plasterboard with a minimum distance of 100mm maintained between the unit and the boxing. 2 The box should be sealed with intumescent mastic at all joints. 3 The Transformer should where possible be located so to be usable. Note: Manufacturers instruction must be consulted if one transformer is to be used to supply a number of units with regard to derating of cabling. 4 Where installed within a roof void, any insulation should be kept away from the box.

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