Types of Insulation


Insulation materials consist of blankets, segments, boards; loose fill or sprayed materials or reflective foil material.

In all cases, the most critical factor for long-term performance is a correct installation system – sadly lacking in New Zealand.

The following table lists most of the types readily available and summarises their suitability for the application listed in the table heading. Some typical names of each type are listed in column 2.


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Other performance criteria to consider are:

Fire Performance:
Glasswool and Mineral Wool are the only non – combustible materials and can act as a fire barrier.
Polyester, Polystyrene & Liquid foams are plastics that usually contain a fire retardant to slow the spread of flame but will burn at relatively low temperatures.
Wool may contain a fire retardant and tends to smoulder with high smoke.
Wool/Polyester blankets tend to burn freely at relatively low temperatures.
Cellulose (paper fluff) contains a variable dry fire retardant and has a history of smouldering and spreading fire when exposed to a heat source.

Moisture Absorption:
Insulation materials lose R-value by about the same percentage as their absorption of atmospheric moisture, which is high during cold winters in most of coastal N.Z, so absorbent materials should be avoided.  Materials exposed to 90% humidity for 4 days typically have the following absorbency:

  • Glasswool, Mineral Wools, Polyester, Polystyrene
  • Wool
  • Cellulose (paper fluff)
9 – 15%

Absorbent materials (>2%) can continue to absorb atmospheric moisture until they reach saturation, where mould, fungi and rotting of surrounding framing timber can occur.

Materials should not deteriorate over the life of the building – deemed to be 50 years by authorities. Factors affecting performance durability include initial installed product density, thickness recovery and atmospheric moisture.  The durability’s listed in the table are based on 30 years of observation of products in service.