How to select insulation

Ceiling insulation can save you 20% on your heating and cooling energy costs.

There are many factors to consider when selecting the right insulation for your home including the product type and most importantly the right r value.

Step 1: Select the right product type

There are two main types of insulation, bulk insulation and reflective foils.

Bulk insulation

Bulk insulation and heat flow

The best type of insulation is bulk insulation. Bulk insulation traps millions of tiny pockets of still air within its structure. These air pockets provide the resistance to heat flow creating the materials insulating effect. 

Bulk insulation is available as batts, blankets and boards or as loose fill which is pumped or blown into the area to be insulated.

Type Description Material

Batts or blanket insulation

Batts or blanket insulation are the best choices for ceiling insulation if you have a flat ceiling and pitched metal or tile roof. The range of batts and blankets that may be suitable for ceiling insulation include; polyester, natural wool, glass wool, and rockwool.

Board insulation

Board insulation can be useful in cathedral ceilings where there is very little space between the ceiling and the roof.

It is available in extruded polystyrene and expanded polystyrene, with or without foil.

Loose-fill insulation

Loose-fill insulation can be used in ceilings, however it can settle over time reducing its effectiveness.


It is available in cellulose fibre, polyester, natural wool and granulated rockwool.

Bulk insulation comes in a range of materials including polyester, natural wool, glass wool and rock wool. The benefits of each type of material are highlighted below.

Benefits Low Toxicity Environmentally
Sound Proof 


✓✓ ✓✓

Natural wool



Glass wool


Cellulose Fibre ✓✓

Extruded or expandable


Reflective foil insulation

Reflective foil insulation works by reducing the radiant heat transfer across an enclosed space. It works most effectively when placed with the shiny side facing an enclosed air space of at least 25mm. The Smartest place to install reflective foil is in walls or as sarking under the roof as it reflects radiant heat away from the interior of the building in summer.

Step 2: Select the right R value

There are many different types of insulation but the most important factor to consider with insulation is its R value.  The R value is a measure of a material's resistance to heat flow (known as thermal resistance).  The higher the R value, the greater the resistance to heat transfer, the greater the insulating effect and the greater the energy savings. Different products with the same R value will provide similar insulation performance.

Remember, it is not necessarily the thickness of the product or the type of material that counts, but the R value.

R values for Victorian homes

Recommended R values for Victoria are shown in the table below.

Minimum Recommended


R3.5 R5








  • For maximum effectiveness, reflective insulation needs to remain clean and dust free, as dust build up will reduce reflectivity. Any gaps in the foil will also reduce its performance
  • It is important not to compress bulk insulation, if it is compressed the air pockets are reduced and the material will lose its insulating properties
  • Installing insulation carries potential risks and requires expert knowledge. Find out more about insulation health and safety

More information

Find out more about insulation with our other how-to guides.