Insulation Types


Insulation types can be confusing. Essentially though, all the insulation products available can be broken down into 2 main insulation types, ‘Thermal’ or ‘Acoustic’ Insulation.

Thermal insulation type products are those that are primarily created to reduce heat (thermal) transfer between two areas, for instance the inside and the outside of a house.

Likewise, Acoustic insulation type products are those that are created primarily to reduce noise (acoustic) transfer between two areas.

However, there tends to always be an amount of crossover, with Thermal Insulation products providing some acoustic insulating properties and vice versa.

Within each ‘main’ insulation type, products can be further divided into 2 sub insulation types, based on the insulating process employed.

Within the Thermal Insulation type there are products that block & absorb heat called ‘Bulk insulation’ and products that reflect heat, called  ‘Reflective insulation’.

Within the Acoustic Insulation types there are products that block sound waves and products that absorb sound waves

In both categories there are also products that are designed to do a little of both, collectively known as composite products.

Thermal Insulation Types:

Reflective Insulation – usually comprises of a thin layer of shiny aluminium foil laminated onto a substrate of plastic or paper, that resists radiant heat flow due to its high reflectivity and low emissivity (ability to re-radiate heat).

To be effective in any way, reflective insulation ‘must’ have the presence of an air layer of at least ’25mm’ next to the shiny surface. Dust settling on the reflective surface greatly reduces performance, so it is essential to face reflective surfaces downwards or keep them vertical. The anti-glare surface of single sided foil sarking should always face upwards or outwards.

The thermal resistance of reflective insulation varies with the direction of heat flow through it.

insulation type

Bulk Insulation – comprises a mass of fibrous material that traps ‘still’ air within little pockets in its structure to resist the transfer of convected and conducted heat through its mass.  Its thermal resistance (R – Value) is basically the same regardless of the direction of heat flow through it.

Composites: – as the name suggests, Composites are an amalgamation of reflective insulation and bulk insulation, designed to take advantage of both insulating methods.

Within each category of insulation there are many different products and materials available.

Reflective Insulation Types:

Wall Wrap / sarking – a thin layer of aluminium foil adhered to a paper or plastic substrate to form a thin, flexible, reflective sheet that is wrapped around the external wall or roof structure of a building prior to the final finish being applied.

The shiny surface must face inwards towards an air gap of at least 25mm for the insulation to perform correctly. Joints between sheets and around wall or roof penetrations such as doors, windows or skylights should be taped to improve the insulating performance and create a moisture barrier between the outside and inside of the structure.

The R – Value stated for reflective insulation is a ‘system R value’, meaning it requires other elements of the structure to achieve the R Value stated, most importantly the air gap.

Bubble Wrap – comprising of 2 layers of plastic that encapsulate small bubbles of air (commonly used as packing material) adhered to a foil facing on 1 or both sides.

Used in exactly the same way as Wall Wrap / Sarking but benefitting from an added insulating effect from the air bubbles within the plastic.  Again joints between sheets and around penetrations should be taped for maximum benefit.

Concertina Batts – a structure comprising of 2 or 3 sheets of foil faced cardboard kept apart from each other

Bulk Insulation Type Products:

Batts & Rolls – The most popular form of bulk insulation is Batts & Rolls, which are designed to easily fit between the most common joist spacing in residential and commercial buildings.

Batts & Rolls are essentially a mass of fibrous material that has been preformed into blocks or blankets using a thermo bonding method. (the use of heat to melt and form the fibres into the required shape)

Batts & Rolls are available in a choice of materials, all of which have their own advantages and disadvantages. The most common being:

            1. Sheeps Wool  – Real sheeps wool is mixed with a binding agent, (usually polyester) to form a batt or roll of bulk insulation material. Natural wool is a very safe, environmentally friendly material with excellent insulating properties. Possibly the only drawback with real Sheeps Wool insulation is the cost. The raw material itself is in high demand within the high fashion textile and carpet industries, hence the cost is high.

            2. Polyester – A safe, non toxic, itch free fiber that because of its non hazardous properties is used extensively in the medical, food, apparel, bedding, carpet & furniture industries, as well as the building industry.

Light weight yet with very high tensile strength, polyester fibers are matted together to create a very effective insulation product.

Again, possibly the only drawback with polyester is that it is not the cheapest product.

            3. Fiberglass (Glasswool) – essentially made from sand and recycled glass bottles, these little fibers made from glass are bound together via a binding agent to create a highly effective insulation material at a very low cost. Because of its low cost, Fiberglass is the most commonly used insulation material in the world.

There are many brands of glasswool insulation available in Australia, knowing the difference can be useful:

            • Bradford Gold Batts – Australian made, to meet the Australian Standards
            • Fletcher Pink Batts  –  Australian made, to meet the Australian Standards
            • TradeFit Insulation  –  Australian made, to meet the Australian Standards
            • Earthwool Insulation – A trade name for Knauf Insulation glassfiber insulation. Made in one of Knauf’s overseas factories, usually USA or Russia.

WARNING! There are also a number of other smaller brands or no name products available that are imported from China and other countries. Usually the cost of these products is very low in comparison to the brands above, however, the quality is also very low, which in the case of insulation really is a false economy. For insulation to be effective and do the job you have paid for, the product must achieve and  maintain the correct thickness long after it has been installed into your home.

Often, due to the effects of use of cheap raw materials, long periods of compression whilst being transported to Australia and ineffective manufacturing techniques, these cheaper products do not achieve the thickness & density they need to meet the R- value stated, or they deteriorate very rapidly causing a loss in insulating effects!

Blow In or loose fill – another type of bulk insulation product that comprises of loose clumps of cellulose (usually mashed up newspapers) or fiberglass fibers that are blown into the loft space or wall cavity.

Like all bulk insulation, the effectiveness of blow in or loose fill insulation is dependent on the products ability to create little pockets of trapped air within its structure. The higher the number of these little pockets of air the more effective the product is at resisting heat transfer through it. Generally, the thicker & denser the product the higher the number of these little pockets of air and therefore the better insulating effect.

However, unlike a preformed insulation product like batts, rolls or sheets, the density, thickness and integrity of the product structure is difficult to control with blow in or loose fill insulation. Therefore, when installing blow in or loose fill insulation, it is imperative that a method of analysing the density, thickness and integrity of the product in place is employed to be sure it will meet the insulating effect required. Likewise, it is also imperative to ensure that the product will not be able to be moved by wind or any other means once installed, as any disruption to the product will change the insulating effect.

Composite Insulation Type Products:  

The most common composite thermal insulation type products are:

Roofing Blanket –  A bulk insulation roll with a foil facing adhered to one side. Most commonly fiberglass or polyester bulk insulation. Specifically designed for use under tin or tiles in residential and commercial buildings.

Foilboard – A polystyrene sheet with a foil facing adhered to one side. Most commonly used in wall or underfloor applications.


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