Updated– Jan 2023
Introduction
This best practice guide advises on the safe installation of downlighters in dwellings and domestic extensions. It informs how these lights can be specified so they comply with the requirements of the building regulations. It covers fire safety, sound insulation, conservation of fuel and power and potential condensation issues.
When using these fittings, it is essential the lighting designer and installer follow the manufacturers’ guidance on issues relating to health and safety.
Fire Safety
Fire Resistance of Floors
Approved Document B Volume 1 of the Building Regulations sets out the fire resistance for the floor. This is normally 30 minutes for low-rise buildings, providing the floor is not a compartment floor.
Tests sponsored by the Department of the Environment, Transport and the Regions (now DLUHC) and carried out by The Timber Research and Development Association (TRADA) provide useful guidance on the performance of these fittings. The tests were carried out on typical timber joisted floors (measuring 3.2 x 4.2m) fitted with up to 24 plastic and metal-clipped fittings of various diameters. All fittings were unprotected and did not cause premature failure in terms of load-bearing capacity, insulation or integrity. Similar tests were carried out by the BRE on downlighter and sprinkler head penetrations in various timber floor types. Reaching similar conclusions to the TRADA research.
TRADA also carried out tests on a 60-minute fire-resisting floor and found there was no premature failure of fittings without additional fire protection. However, due to the very limited scope of the testing, it was considered there was still a need for downlighter protection on 60-minute floors.
These tests cannot be seen as being representative of floor types that may incorporate engineered ‘I beam’ or open steel web joists. This is due to them having little ‘sacrificial’ timber and so they may rely almost entirely on the integrity of the ceiling lining to prevent failure in fire. Tests by one manufacturer have indicated that a similar performance to traditional joists can be achieved as did the BRE tests which also included these floor types. But due to the limited nature of the tests they cannot be regarded as conclusive and protective measures may still be needed in this type of floor.
Clearance to Combustible Materials
Downlighters can generate significant levels of heat when they incorporate halogen fittings, it is therefore essential that a safe clearance is maintained from any combustible materials. This may preclude the use of downlighters in sloping ceilings where adequate clearance cannot be achieved without creating unacceptable levels of cold bridging. In such situations, it may be possible to design a compliant arrangement by using insulating enclosures or making use of CFL (compact fluorescent) or LED lamps.
Where the downlighter is exposed within a loft space used for storage, combustible materials may accidentally be laid over it and so pose a risk for the outbreak of a fire. In such situations, good practice is to fit clearly visible protective covers as a precaution.
Sound Insulation
Internal floors within dwellings
Building Regulation Part E 2003 (as amended) introduced new controls on the sound-insulating properties of floor construction within dwellings which revised requirements for separating floors in existing dwellings. The new standard requires floors to achieve a sound reduction of 40 R w dB. Raising the question as to whether the installation of downlighters could adversely affect the performance of floors.
Advice from experienced acoustic consultants confirms the installation of these fittings has relatively negligible effects on sound insulation, with tests suggesting they will only reduce levels by 1– 2 db. It would therefore seem reasonable that downlighters can be used on internal floors (note not party floors) without any additional measures being necessary.
Separating floors between dwellings
The use of downlighters in separating floor constructions is covered in the Robust Details guide, which states a minimum ceiling void of 75mm is needed. Installation should be in accordance with manufacturers’ recommendations and include the following:
- No more than one light per 2m2 of ceiling area in each room
- At centres not less than 750mm
- Openings in the lining should not exceed 100mm diameter or 100 x 100mm if square.
- Only downlighters that have been assessed in accordance with the procedure described in the Robust Details guide Appendix F are acceptable.
Separating floors not covered by Robust Details should not be used unless satisfactory evidence is provided of compliance with the Building Regulations.
Thermal Insulation
Cold bridging
It is commonly noted that newly built extensions and dwellings have a significant number of uninsulated patches around the downlighter fittings in the ceilings. The cumulative effect of this in terms of heat loss can be substantial. The BS EN 60598-1 symbol in diagram 1 below is often used to show that unprotected fittings are not suitable for use.
BR443 2019 (conventions for U-Value Calculations) makes provision for assessing uninsulated areas to give an area weighted average U-value for a roof or floor. This may result in an increase in the insulation thickness elsewhere to compensate for the gaps around the fittings. Calculations are rarely available when assessing smaller projects and other measures may be more appropriate to demonstrate compliance. The “boxing in “detail shown in diagram 2 below is an acceptable solution for Part L.
Most commonly available low voltage or halogen spotlights (Dichroic lamps) allow much of the radiated heat to dissipate through the back of the lamp. This can cause significant heat build-up problems unless they are fully protected. However, there are some aluminium lamps that direct heat through the lens of the lamp. They need a smaller pocket of insulation to safely accommodate the fitting. Unfortunately, there is no way of ensuring that bulbs are not interchanged and so cause potential future heat build-up problems if changed from one type to the other.
Light-emitting diode (LED) models do have the advantage of creating very little heat (see ‘efficient lighting’ below). This makes it possible to cover the unprotected fittings with insulation and eliminate cold bridging entirely.
Air Leakage
The energy efficiency of a new dwelling or extension is reliant on the quality of the construction to minimise the loss of heat due to uncontrolled air leakage. Most new dwellings undergo air leakage testing on completion. Proper specification of downlighters, where they penetrate ceilings to insulated roofs, is important to ensure a reasonably airtight seal. This may be by using an integrally sealed unit or fitting a hood or boxing over the fitting. An example is shown in diagram 2. (See also sections on compatibility with roof underlays and clearance to combustible materials)
Efficient Lighting
Building Regulations Approved Document L gives guidance on the minimum provision of energy-efficient lighting. Where installed in a new or existing dwelling, each internal light fitting should have lamps with a minimum luminous efficacy of 75 light source lumens per circuit watt.
Types of Fittings
Condensation Issues
The introduction of high-performance ‘vapour permeable’ roofing underlays permits designers to reduce or omit provisions for cross ventilation as a precaution against the build-up of interstitial condensation in the roof void. To comply with the building regulations the design and installation of this type of underlay must accord with BS: 5250:2002 or the installation details in BRE and BBA certificates. The ceiling to the roof must be properly sealed to minimise the passage of water vapour to the roof space.
Standard open downlighters are unlikely to be able to meet this requirement; therefore, fittings that are specifically designed for this use must be used. Alternatively, a sealed box or hood as detailed above will also meet the requirements of the Building Regulations. However, it should be noted standard ‘fire hoods’ are not likely to be suitable for this purpose.
Key points to consider.
- Relevant test evidence for the product and floor construction from the manufacturer’s details.
- Downlighters can generate significant heat when fitted with halogen lamps. Maintain safe clearance from any combustible materials.
- Use Robust Details when installing lights in separating floors.
- Heat loss in roofs can be substantial. Ensure fittings are suitable for the location.
- Use light-emitting diode (LED) lamps wherever possible to minimise energy use and heat build-up.
- Carefully specify downlighters where they penetrate ceilings to insulated roofs to prevent air leakage.
- Properly seal light fittings to minimise the passage of water vapour to the roof space.
Conclusion
We hope that the above information will enable you to confidently specify the use of downlighters without conflicting with any of the relevant sections of the Building Regulations. You are welcome to contact your Local Authority Building Control Office for further information on this subject.
Produced with assistance from the LABC Hertfordshire Technical Group
