Passive Design

Designing the building and the spaces within it to benefit from natural light, ventilation and even temperatures.

Installing insulation

The correct installation of insulation is critical.

On this page:

  • precautions when inistalling insulation
  • installing insulation generally
  • specific installation instructions
  • reducing the effects of thermal bridging

NZS 4246 Energy efficiency – Installing insulation in residential buildings provides guidance on insulation use and installation so that thermal performance requirements and durability of the building envelope elements are achieved.

Precautions when installing insulation

Installing underfloor insulation has resulted in some fatalities. Take the following precautions when installing insulation:

  • Do not allow EPS to come into contact with PVC-sheathed electrical cables as this results in migration of the plasticiser in the PVC, causing it to become brittle and eventually breakdown. Create a physical barrier such as an air gap or installing conduit for electrical cables.
  • Do not allow insulation to get wet as this will reduce performance.

Installing insulation generally

When installing insulation:

  • follow the manufacturer’s recommendations for safety and handling
  • wear recommended protective clothing and masks.

Install insulation to:

  • fit firmly without edge gaps
  • be clear of downlights unless zero clearance downlights are installed
  • be clear of fixtures that get hot such as flues and transformers (refer to Electrical Code of Practice ECP 54)
  • be clear of water tank overflow trays
  • have a minimum 25 mm air gap between insulation and roof underlay in skillion roofs.

Specific installation instructions

Blankets and segments

Fit blanket and segment bulk insulation firmly between framing without gaps. They must not:

  • be compressed
  • have folds or tucks
  • sag within wall framing cavities – the blanket or segment should preferably be the same thickness as the cavity
  • be installed into timber framing that has a moisture content of over 20%.

Loose fill

Install loose fill insulation so that it:

  • cannot be shifted by air movement
  • is laid in an even thickness
  • is laid with sufficient depth to allow for settlement
  • is not compressed
  • is kept away from downlights.

Polystyrene boards

Rigid polystyrene board insulation must:

  • be laid over a damp-proof membrane when used under a concrete slab on the ground
  • be separated from internal spaces by a lining material
  • be fitted tightly against the underside of the flooring when fitted between floor joists
  • be fitted tightly between cavities
  • not come into contact with PVC (such as TPS wiring).

When used as a cladding, rigid board insulation should be installed in accordance with NZS 4246 and the manufacturer’s instructions.

Insulating plaster

Insulating plaster must be applied to the design thickness of the plaster mix and in accordance with the manufacturer’s instructions. When applied externally, it must be protected from the weather by a suitable weatherproof coating.

EIFS

EIFS cladding systems are to be installed in accordance with the system supplier’s instructions.