Property Clinic: the problem with downlights

All your property queries answered

Draughts from downlights: insulation should not cover a spotlight as they can overheat and blow. Photograph: Thinkstock

Draughts from downlights: insulation should not cover a spotlight as they can overheat and blow. Photograph: Thinkstock

Wed, Jun 25, 2014, 17:11

Q I had my house renovated last year, which involved insulating the entire house, some internal and external, a new boiler and a new kitchen, shower room and study.

The kitchen, shower room and study comprised the flat roof extension on the side of the house. It was stripped down to an empty shell and was rewired replumbed and insulated. The ceiling was insulated with 80mm Kingspan between the joists and 60mm plaster board with insulation secured to the joists and shimmed.

The architect asked if we wanted downlighters and it was agreed that they would be installed. There are a total of 21 downlights between the three rooms. I noticed as the weather got colder and windier after last summer that the kitchen, while quite warm and comfortable, did not seem to be holding the heat as much as I expected. I began to feel draughts and was surprised to find that there were draughts coming out of each of the downlights. To install the lights a hole was drilled through into the cavity above the joists to gain access to the electric cables. Nothing was installed to prevent draughts.

I contacted the builder and he suggested that I use a “cup”, in the area above the ceiling, to cover the access hole. This would work in an attic but not with a flat roof! He has no other suggestions.

What would be the best thing to do?

New downlights, if they exist, that don’t allow draughts.

Block the holes and get pendant lights. Or something else.

Block the existing holes with fibre insulation in some way.

Learn to live with draughts on my head.

I would be very interested in your views on my problem.

A It sounds as though you have had extensive renovation work done to your property and it is unfortunate you are experiencing problems so soon after making this considerable investment in your home. You may have already found that people commonly have problems with these type of lights.

Recessed lights are not a good detail in a cold deck flat roof construction like yours. The cold air necessary to ventilate the roof structure, can infiltrate the external fabric, through the holes created for the downlights. Contrastingly, the opposite effect can also occur where a downlight can act like a chimney and draw out warm, rising air from a room, up into the cold roof void.

Insulation should not cover a spotlight as they can overheat and blow. However, the risk of fire is very low as the insulation is fire and heat resistant. So downlights need a certain minimum ventilation for heat generated by the lighting to dissipate. The manufacturer’s instructions will give a guide as to the minimum distance the insulation should be kept from the light fitting. However, this can result in what is termed “cold bridging” and reduce the thermal efficiency of the roof structure.

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