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Smart guide

Downlights and recessed lights

Older technology downlights require a hole in your ceiling and insulation that lets your warm heated air escape into the roof space.

Downlights – make smart choices

While downlights, also known as recessed light fittings, have been a popular option in recent years, some types that are on the market can undermine the effectiveness of your ceiling insulation.

Choose the type of downlights you install carefully, because some require ceiling insulation to be kept clear of them. This creates easy paths for heat and moisture to escape into the roof space. Advanced downlights can be covered with insulation stopping the heat loss. There are downlights that are specifically made for wet areas that prevent the warm humid air from going up into your ceiling cavity – ask your electrician or lighting retailer for further details.

LED lighting on the Gen Less website has information about energy efficient lighting.

The problem with older technology downlights

Older technology downlights reduce the effectiveness of your ceiling insulation by creating a hole into the roof space above. This is made worse by the need to leave a safety gap between some downlights and insulation in the ceiling.

Incandescent or halogen bulbs used in downlights get very hot, as do any associated transformers, so fire is a risk. Safety regulations require a 150mm gap between older technology downlights and insulation, and the cans should never be covered with insulation with these downlights. Collars are available which keep the insulation away from the downlights – if you have loose fill insulation, check that you have these in place.

The result of these holes is that your warm heated air is drawn up into the colder roof space and your ceiling insulation cannot work as well as it should. The more of these older technology downlights you have, the less effective your ceiling insulation will be.

The New Zealand Standard for the installation of insulation (NZS4246: Energy Efficiency – Installing insulation in residential buildings: 2006) shows that an older technology downlight every five square metres reduces insulation effectiveness by 10 per cent. This is because around each downlight there is about a quarter of a square metre with no insulation where heat can escape almost completely unrestricted.

Check the rating of any downlights you have installed. Some downlights are CA-rated (for “closed abutted”), which means that insulation can at least be installed close to the light can. Insulation Contact (IC) and Insulation Contact – Fire Resistant rated (IC-F) ones can have insulation installed up to and over them, provided the insulation can cope with temperatures up to 90°C.

IC-F rated downlights are not necessarily fire rated – if you need fire-rated light fittings (eg for a fire-rated ceiling in an apartment), you will need to check the manufacturer’s data sheet to see whether they are suitable for your particular application. They need to be fitted in strict accordance with the manufacturer’s instructions.

IC and IC-F rated downlights will lose the least amount of heat in the roof space. IC-F rated downlights should be used in bathrooms and kitchens, and homes with loose fill insulation, as they are designed to have very small gaps around them to keep out debris and prevent moisture entering the roof space.

Alternatives to consider

To get the most benefit from ceiling insulation, only use downlights in lower storeys.

If you want to use downlights in an external ceiling make sure you use IC or IC-F rated downlights. Older technology unrated downlights are no longer permitted to be installed. Check the box or the back of the fitting for the downlight rating – newer ones should have a rating label firmly attached.

If you have older technology or CA-rated downlights:

  • consider replacing them with surface-mounted fittings especially if you are renovating. You may be able to source a surface-mounted fitting that will cover and seal the downlight hole, or if you are undertaking major renovations, re-do the ceiling plasterboard
  • replace old and CA-rated ones with IC or, preferably IC-F rated LED downlights that can be covered with insulation. IC-F rated downlights should be used in bathrooms and kitchens, and homes with loose fill insulation.
  • upgrade your ceiling insulation to compensate for the lost warmth.

There are a wide range of IC and IC-F rated LED downlights available on the market. 

If you are not sure of the type you need, check with a registered electrical contractor.

Note that this document is published by the Ministry of Business, Innovation and Employment Chief Executive as Guidance under Section 175 of the Building Act 2004. This is a guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case.