lighting

Fire Rating Lighting

In this post we try and answer when fire rated fittings or fire hoods are required. As with any thing relating to building control it is very important that you consult with your local building controls and fire office from the outset of the project.

Why do we need fire rated light fittings?

Fire rated fittings are specified to maintain the integrity of the fire rating of a buildings typically these are 30, 60 & 90 minutes of protection. Where you have a cut out for a down light this will be seen as a weak point for fire and smoke to access in to other parts of the building from. Fire rated down lights have a seal that expands in the event of heat to stop the passage of smoke as well flames. There is some debate as to how effective some fire hoods are but to mitigate responsibility contractors tend to er on the side of caution and install them any way. There has been some misconception that fire hoods were necessary for 12v halogen lamps due to the heat of the lamp. This is not the case.

Where do I need fire rated lighting?

Part B of the Building Regulations state that any residential dwelling with the top floor height of up to 18m above the ground should have ceilings resistant to fire to up to 60 minutes.

Part B fire safety.

http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partb/

Approved Document B – Building Regulations
Paragraph 11.2
‘If a fire separating element is to be effective, then every joint, or imperfection of
fit, or opening to allow services to pass through the element, should be adequately
protected by sealing or fire-stopping so that the fire resistance of the element is
not impaired’.
Appendix A table A1 and A2 (specific provisions of test for fire resistance
of elements of structure)
Fire resistance of structural floor in upper storey of 2-storey dwelling house-
minimum provision 30 minute integrity (based on load bearing)
Similar requirement for other dwelling houses with top floor not more than 5m
above ground, but increasing to 60 minute integrity if top floor is between 5m and 18m above ground

How fire rating lighting works

Fire rated fittings which have been tested and approved  by independent test houses such as BRE typically have an in-tumescent material built in which expands and closes the hole when heated. From a lighting design perspective the range of fire rated fittings is limited which is why other methods of maintaining the fire rating are used.

Fire hoods

If a down light has not been tested and approved then a fire hood which covers the fitting and provides fire rating is recommended. The main issues with fire hoods is that they are very good at preventing fires escaping which means that they are excellent at trapping the heat which for LED lamps is a disaster as they will over heat and fail. They can also be very difficult to instal as typically you will be required to fit the fire hood in to the hole from below and then fix the fire hood in place.

Fire box

A firebox is an enclosure which fits around the fitting which is constructed from the same fire proof material as the ceiling. This is seen as the most reliable method as provides a rigid structure and allows the LED to breath as the fire box will be designed around the fitting. This method really only works if you have access from above or below for a new build.

The requirements for residential and commercial lighting vary and fire rated fittings are not needed for all installations, typically the responsibility falls with the installing contractor.

If you do have any questions on fire rated fittings then please get in touch.