Down with da hood

Halogen downlighters still prove popular for many projects, but there are certain circumstances where extra precautions have to be taken.

As these precautions have life-safety implications, it’s essential to be aware of the risks and the solutions.

For example, as soon as you cut a hole in a ceiling you invalidate the fire rating of the ceiling materials. Any such unprotected aperture could allow flames, heat and smoke to quickly pass through the ceiling to other areas of the building, even if the rest of the ceiling is designed to withstand the spread of flame for 90 minutes.

In purpose-built commercial buildings, this isn’t a problem because the floor slab between storeys provides the fire protection. However, many commercial properties are converted dwellings, so the downlighters may be installed into a roof space.

This raises a number of issues, including the fire rating of the ceiling, the potential for noise transmission and, in certain circumstances, the potential for moisture to move into the roof space. Of course, all these issues also relate to domestic properties if downlighters are being installed into the roof space.

In relation to fire safety, Part B of the Building Regulations requires the fire integrity of the ceiling to be reinstated when downlighters are installed. In the past, this has required that a fire hood be fitted over the top of the downlighter so that flames and smoke cannot spread through the aperture.

From the installer’s point of view, though, fire hoods are expensive and fiddly to fit, thus extending the time and cost of the project.

More recently, downlighters with integral fire protection have been introduced to simplify installation and reduce costs. They do cost more than a standard downlighter, but a lot less than a downlighter with separate fire hood.

As with most innovative products, there are both high-quality versions of these products and cheap copies that won’t deliver the required performance. Consequently, not only are some of these products downright dangerous, they could also embroil contractors in litigation for failing in their duty of care.

The only way to avoid such problems is to be aware of what these products should do and what standards they need to comply with. Armed with this information, it’s then simply a matter of asking the manufacturer for proof of compliance.

There are three key aspects of performance to look out for. The first and most important is clearly the ability to prevent the spread of fire. In addition, they should inhibit the spread of airborne and impact-generated sound and eliminate the spread of moisture to prevent condensation.

In the case of fire rating, such products should be able to prevent the spread of flame in compliance with BS 476. This is achieved through the incorporation of intumescent fire-retardant seals that expand in the event of fire. As they expand, they restrict the flow of oxygen through the cut-out void and provide a full 90 minute fire rating without the need for additional components.

One seal is located in the cap of the downlighter so that the cap is sealed, while the other seal fits round the downlighter’s circumference to seal the

cut-out. The cap seal also features a seal retainer that provides a physical barrier and prevents the seal expanding downwards into the downlighter body. Instead, the expanding seal is forced upwards into the ventilation holes in the top of the downlighter.

Sound transmission

To avoid sound transmission, the downlighters should be tested to BSEN ISO 140-3 (1995) and to BSEN ISO 140-6 (1998). Compliance with these standards is achieved by using a rigid steel downlighter body with heavy-duty springs that clamp the luminaire securely to the ceiling.

In many projects it will also be sensible to seek compliance with the requirements of Robust Designs, a scheme introduced to ensure that acoustic considerations are addressed before construction begins. Thus, there is less likelihood of being called back to rectify problems with sound transmission at a later date.

Moving moisture

Moisture problems are most often associated with domestic properties, but it’s worth giving them a quick mention. Where recessed downlighters are used in kitchens, bathrooms and shower rooms, there is the potential for moisture-laden air to be drawn through the downlighter on convection currents created by the heat of the lamp.

This can lead to condensation and cause structural damage, so the National House Building Council (NHBC) has established standards for the airtightness of downlighters. In the case of downlighters with integral fire seals, the ability to add an optional neoprene moisture seal ticks all of the boxes.

Clearly, any downlighter that addresses all of these considerations needs to be a complex and well-engineered item of equipment.

Cutting corners anywhere in the design or in the quality of the materials used could have the effect of invalidating its performance in one or all of the parameters that have been discussed.

I would argue that in the case of life-safety products, and implications of product failure, there is no room for complacency on the part of those responsible for procuring the products.

Other fire concerns

Another fire-related issue associated with downlighters in roof spaces is the build-up of heat caused by loft insulation

in a dwelling or converted property. In a false ceiling there should be sufficient air movement to dissipate the heat from the lamp, but if the downlighter is pressed up against a layer of insulation in a roof space, this won’t be the case.

Also, tests have shown that the surface of a halogen downlighter can reach a temperature of 550°C under conditions where air is not allowed to circulate close to the light source to remove heat. This is hot enough to ignite loft insulation material within around 30 minutes of contact.

This is a very real danger. Research by fire authorities in Australia has led to estimates of one loft fire being started by recessed halogen downlighters every three to five days, and there’s no reason to believe the same potential doesn’t exist in the UK in circumstances where such fittings aren’t fitted properly.

A quick and simple solution is to install an insulation support box between the fitting and the insulation. Effectively, the box covers the fitting and provides enough space for air to circulate so the fitting doesn’t overheat, while the insulation layer remains intact and the thermal insulation of the property is not impaired.

For all of these reasons, I would urge contractors to take a close look at their procedures for installing downlighters and ensure they are taking a thorough look at all of the risks involved.

My company sells downlighters of all kinds, and we certainly don’t want to discourage their use. But we do want to be sure they are being used safely.