Is your insulation adequate?

Good insulation makes a big difference to a home's warmth, comfort and health. Unfortunately, nearly 60% of our homes have inadequate ceiling and underfloor insulation[1] - so it pays to check whether your insulation is doing what it should.

The good news is that it's fairly straightforward to identify whether your existing insulation is ‘adequate' or doing a good job - simply follow the checklists below. Depending on what you find, you may need to totally replace your insulation or top it up.

On this page:

Health and safety when checking insulation

There are some health and safety things to be aware of when checking your insulation - for starters you'll need to climb into your ceiling space and under your house. These are outlined in the NZS 4246:2006 insulation installation standard. If in doubt, talk to a professional.

Check your ceiling insulation

For ceiling insulation check:

  • is there any ceiling insulation?
  • is it thick enough? It should be at least 120mm thick (higher than your ceiling joists) - if it's not, get your insulation topped up.
  • is it gap-free? There should be no visible gaps between the insulation and the ceiling joists or at joins of insulation pieces and no sections of insulation should compressed, squashed or tucked in.
  • is it dry? Damp insulation is much less effective. If it's damp, fix the source of the moisture, and remove and replace the affected insulation.
  • is it vermin-free? Vermin infestations (e.g. birds or rodents nesting) can damage your insulation. Get the infestation sorted, and remove and replace the affected insulation.
  • does it cover the whole area? The insulation should cover the entire ceiling, including the manhole cover, except for areas above the eaves, any porches or any garage or other inhabitable space.
  • is it clear of your downlights? There must be a 150 mm safety gap around down lights, and other heat sources, for fire safety reasons - it's really important to check this occasionally and get it sorted. Find out more about safe installation of insulation around down lights, chimneys and flues.

Consider replacing recessed downlights with non-recessed lights if you want to avoid the heat losses associated with holes in your ceiling and gaps in your insulation.

If there isn't an accessible ceiling space, talk to a qualified builder about whether it is possible to insulate your ceiling.

Check your underfloor insulation

For underfloor foil insulation - if it's fixed with staples, avoid touching the foil unless you've had it checked by a registered electrician (if an electrical cable was accidentally stapled when it was installed, there's a risk the foil could electrocute you). Check:

  • that it is either stapled to the underside of the floor joists, or draped over the floor joists with a sag of 100mm or more
  • that the foil is still in good condition, i.e. not tarnished, very dirty, torn, delaminated or otherwise deteriorated
  • that, if attached to the underside of the floor joists, the foil is still well-supported by staples which should be punched flush to the foil surface
  • that all joins between foil runs are overlapped and sealed with adhesive foil tape
  • that the airspace between the floor and the foil is properly sealed, including along the floor perimeter and at the points of pipe penetrations
  • that, for houses with brick-veneer cladding, the airspace between the floor and the foil is properly sealed off from the brick-veneer cavity
  • that it covers at least all parts of the suspended floor which are accessible.

For underfloor bulk insulation check:

  • that it is at least 50mm thick
  • that there are no visible gaps between the insulation and the floor joists or at joins of insulation pieces
  • that the insulation is dry and not infested with vermin (e.g. birds or rodents nesting)
  • that the insulation is securely installed flush against the underside of the flooring (e.g. floorboards)
  • that it covers at least all parts of the suspended floor which are accessible.

For underfloor polystyrene insulation check:

  • that it is at least 50mm thick
  • that there are no visible gaps between the insulation and the floor joists or at joins of insulation pieces
  • that the insulation is securely installed flush against the underside of the flooring (e.g. floorboards)
  • that it covers at least all parts of the suspended floor which are accessible.

Your underfloor must be accessible (i.e. more than half a metre off the ground) to be able to put in new insulation.

Check your wall insulation

Wall insulation cannot easily be inspected without removing either the external cladding or the internal wall lining. If you are doing this check:

  • that the insulation is as thick as the wall cavity (in most cases this will be 94-100mm) without being compressed, squashed or tucked in
  • that there are no visible gaps between the insulation and the timber framing or at joins of insulation pieces
  • that the insulation is dry and not infested with vermin (e.g. birds or rodents nesting)
  • that all external walls of occupied rooms and all walls between occupied and unoccupied rooms (e.g. garage) are insulated.

You can check to see if you have wall insulation by drilling inspection holes through the internal wall lining, or when your registered electrician is removing power points or light switches in external walls.

Houses built before 1978 did not have to be insulated, so unless someone has added it later, you can assume you don't have any in your walls. And while insulation has been mandatory for all houses built since 1978, surveys have found that about a fifth of them don't have wall insulation, so it's a good idea to check if you get the opportunity.

Notes:

[1]Clark, S.J., Jones, M. & Page, I.C. 2005. New Zealand 2005 House Condition Survey. Wellington: BRANZ

From the Resource Centre

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