Insulation reduces the flow of heat into the house in the hot seasons and out of the house in the cold seasons.


Insulation reduces the flow of heat into the house in the hot seasons and out of the house in the cold seasons, keeping the house cool in summer and warm in winter.

A well-insulated and well-designed home provides year-round comfort, cutting cooling and heating bills by up to half. This, in turn, reduces greenhouse gas emissions.

Passive solar design techniques should be used in conjunction with insulation. For example, if insulation is installed but the house is not properly shaded, built up heat can be kept in by the insulation creating an ‘oven’ effect. Draught sealing is important, as draughts can account for up to 25% of heat loss from a home in winter.

Insulation can help with weatherproofing and eliminate moisture problems such as condensation, and some types of insulation also have soundproofing qualities.

The most economical time to install insulation is during construction, although it is possible to retrofit and existing building by adding insulation to improve energy efficiency.

Most common construction materials have a low insulating value, but some require little or no additional insulation. Such materials include aerated concrete blocks, hollow expanded polystyrene blocks, straw bales and rendered extruded polystyrene sheets.

Material R-values are supplied with insulation and refer to the insulating value of the product alone. The higher the R-value the better the thermal performance.

The appropriate degree of insulation depends on climate and building construction type.

There are basically two types of insulation material: bulk and reflective.

Bulk Insulation

Heat Loss
Heat Loss Diagram

Bulk insulation reduces the flow of convection and conduction heat by pockets of air trapped in the fibre or particles of the material.

Typical types include:

  • Batts and blankets made from rockwool, fibreglass, acrylic fibre or wool.(A strawbale wall is a good example of a wall system with built in bulk insulation).
  • Loose fill material such as treated waste paper.
  • Rigid lightweight boards such as polystyrene and polyurethane. (Structurally insulated panels with a polystyrene core or SIPS are a good example of a well insulated building system).

Reflective Insulation

Heat Gain
Heat Gain Diagram

Reflective insulation reduces heat transfer by reflecting radiant heat on the warm side. Reflective insulation must have an air gap adjacent to it.

Typical types include

  • Reflective foil laminate made from aluminium foil laminated to a stiffer backing such as polystyrene.
  • Reflective foil laminated to one side of bulk insulation sometimes know as “Anticon”.
  • Reflective foil laminated to a plastic bubble wrap material.
  • A thicker reflective foil with perforations known as ‘Vapour permeable reflective foil sarking’

The ceiling/roof area is the major path for heat loss and gain. This area is the most important part of a building fabric to insulate. The walls and floors should also be insulated if framed or in combination with thermal mass. Reverse brick veneer with thermal mass on the inside and a well insulated framed wall to the outside is a clever use of brick veneer construction.

Heat loss diagram from