Checking ceiling insulation

It's worth checking your insulation occasionally to ensure it is still working effectively. It may never have been up to today’s standard, may have been damaged by people working in the ceiling space or slumped towards a heat source, creating a fire risk.

Watch:  How to check your ceiling insulation | 2:36 min

DIY insulation check

If you can do it safely, get a step-ladder and peek through the hatch of your ceiling into your roof space to see if you have insulation.

You will need to add a top-up layer of insulation, if your existing insulation:

  • is less than 12cm thick (it should be thicker than the height of the ceiling joists)
  • doesn't cover the whole ceiling
  • has gaps in it, or places where it is squashed or tucked in.

You need to remove the old insulation and start again with a new layer, if:

  • it is wet or damp in areas
  • has been damaged by rodents or birds.

Also check safety gaps between insulation and heat sources like recessed downlights, chimneys, flues or extractor fans for fire safety including:

Heat sourceSafety gap needed
Recessed downlights NOT marked either CA80, CA90, CA135, IC, IC-F or IC-4 (look for a label on top). This generally includes all downlights installed before mid-2012, but may also apply to some downlights that have been installed more recently. 100mm minimum gap (unless manufacturer’s instructions are available and say otherwise).
Recessed downlights marked either CA80, CA90, CA135 (look for a label on top) Compatible bulk insulation can touch the sides of the downlight, but must not cover it. Loose-fill insulation typically requires a guard or barrier to prevent it from getting in direct contact with the downlight.
Recessed downlights marked either IC, IC-F or IC-4 (look for a label on top) Compatible bulk insulation can cover the downlight. Loose-fill insulation typically requires a guard or barrier to prevent it from getting in direct contact with the downlight.
Downlight transformers, ballasts and drivers
Must be either placed on top of insulation or require a 50mm minimum gap.
3-in-1 fan/heat/light units 100mm
Other lamps in the roof space 200mm
Unducted extractor fans and rangehoods (insulation can get trapped in these, causing the motor to overheat) 200mm
Ducted extractor fans and rangehoods 50mm to electrical compoonents (e.g. fan motor)
Brick or concrete chimneys 50mm

Metal chimneys or flues


Refer to New Zealand Standard NZS 4246:2016 Appendix A for full details of the requirements.

If you have loose-fill insulation, you should use permanently fixed collars made of fire-resistant materials. The collars should extend at least 75mm above the insulation layer.

Clearances - NZ Standard for installing insulation: Appendix A - Tenancy Services website

Professional insulation check

If you can't check your own insulation, or aren't sure if you need any, get a professional to come and have a look for you - this service is often free of charge. Look for an installer who:

  • works to the New Zealand insulation installation standard NZS 4246:2016
  • and has completed the insulation installer training of the Insulation Association of New Zealand (IAONZ).

 NZ Standard for installing insulation NZS 4246:2016

Insulation in rental homes

In rental homes, insulation must meet the Residential Tenancies (Smoke Alarms and Insulation) Regulations 2016.

Insulation regulations for rental homes - Tenancy Services website