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The thought is that if you cut a hole in the ceiling it provides a route for fire to enter the ceiling void and may lead to damage of the supporting structure. So if you cut a hole in a ceiling should you use a fire hood or fire rated downlight? Well No.
We've spoken to the Office of the Deputy Prime Minister (ODPM) who set out the building regulations and in fact they've confirmed there has been no modification of the wording in Part B of the building regulations regarding lighting for a number of years. The section, as it stands, was written advising against the use of recessed lights that form part of a ceiling with thermoplastic diffusers. Think of a 70's office i.e. in an episode of The Sweeney. Think of the suspended ceiling with those flat or prismatic sheet lay in diffusers - this is a luminaire that forms part of a ceiling that has a thermoplastic diffuser!
So if you don't have a 70's suspended ceiling, where the lights form part of the ceiling and lighting that has a plastic diffuser that will melt and drip molten plastic onto you when it gets hot, are you in the clear? Well No.
Because we suggest you think about your own safety and the safety of people around you. So here are our recommendations...
Cut your hole. If it has a double layer of plasterboard it's either a fire rated "compartment" or it's there to reduce noise. Fit a fire hood or fire rated downlight.
Also consider these points...
If you're putting lights in an integral garage with accommodation above - use a fire hood or fire rated downlight.
If you live in a 3 storey house (especially with only one flight of stairs) - use fire hoods or fire rated downlights.
If you live in a conversion i.e. a larger Victorian or Edwardian house that been converted into flats - use a fire hood or fire rated downlight if there is a separate dwelling above your accommodation and hope, if you have neighbours below, that they use fire hoods or fire rated downlights too.
This is not an exhaustive list, there are other areas where you could use fire hoods or fire rated downlights. But here are some spaces where they are not required...
Bathrooms, bedrooms and other spaces with only the roofspace (loft) above them.
Hallways - if there is no fire door between levels in a house there is no fire compartment. It laughable to suggest that fire will wait to burn through a downlight when it could simply rush up the stairs!
Fire hoods or fire rated downlights are not designed for use in insulation. Be clear about this point! If your roof structure has plasterboard with rigid phenolic or urethane insulation (i.e. Kingspan) you cannot cut a single hole through the plasterboard and insulation and install a downlight. The heat from a normal 12v or mains lamps has nowhere to go and will "cook" the fitting, wiring and insulation and create a fire hazard through short circuit or combustion of other materials. In this type of installation you should cut a void at least 200mm² square in the insulation (300mm² for fittings where a transformer needs to be located in the void). If you don't want to cut a big void in your insulation your only choice is a cool running LED lamp.
The hoods cover the light fitting and reinforce the fire protection and that's why they are used. These have a hood of 160mm in diameter and a depth of 130mm - so should cover the majority of recessed ceiling fittings. The rim of 50mm provides additional protection. This fire hood can be fitted either from above or below.