Passive Design

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

Options for roof insulation

Ceilings/roof spaces are generally insulated using blanket/segment or loose fill insulation.

On this page:

  • Insulating timber-framed roofs
  • Steel-frame roofs
  • Insulating skillion roofs

Blanket or mat (segmented) insulation is available in glasswool (fibreglass), wool, polyester, wool/polyester mix, and mineral wool.

Loose fill insulation is available in glasswool, mineral wool, macerated paper and wool.

For information about performance, durability and environmental properties of each material, see our insulation materials factsheet(PDF) and the materials section of this site.

Timber-framed roofs

Install ceiling space insulation between joists over the ceiling lining where possible as this is where the greatest heat loss occurs. A second layer should be laid over the framing to reduce the effect of thermal bridging.

Steel-framed roofs

The general principles of roof insulation are the same for steel-framed roofs, although there are some slight changes required to where and how insulation is installed in practice for the best results. For more information see the BRANZ publication Building Basics Steel Framing.

Skillion roofs

For skillion roofs with exposed rafters, install insulation over the ceiling lining between purlins purlins must be sized to provide sufficient depth for the required thickness of insulation plus a 25 mm minimum air gap between the insulation and the flexible roofing underlay.

For skillion roofs with concealed rafters, install insulation between rafters the combined rafter/purlin depth is likely to be sufficient to ensure that a 25 mm minimum air gap is achieved.

Note: For both exposed and concealed rafter skillion roofs, an air barrier must be installed over a timber-boarded ceiling to prevent air movement into the roof framing.

 

Updated: 23 October 2018