What is adequate?

To identify whether your existing insulation is ‘adequate' or doing a good job, check the list below. Depending on what you find, you may need to totally replace your insulation or top it up.

For ceiling insulation check:

• that it is at least 120mm thick
• that there are no visible gaps between the insulation and the ceiling joists or at joins of insulation pieces and that no section of insulation are compressed , squashed or tucked in
• that the insulation is dry and not infested with vermin (e.g. birds or rodents nesting)
• that it covers the entire ceiling, including the manhole cover, except for areas above the eaves, any porches or any garage or other inhabitable space.

For underfloor foil insulation 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.

For 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 it is as thick as the wall cavity (in most cases this will be 94-100mm)
• 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.