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Thermal Insulation is required by law to be installed to all new homes in WA. Insulation is rated according to it's effectiveness or thermal resistance by its R code, the higher the R code the more effective the product .Normally your home needs roof insulation rated  R 2.5 or higher however if you are building in an area prone to extreme temperatures you may require an R code of 3 or more (maximum 5). There are numerous products available and of course various price tags. You also need to take into account what your roof cover is, tiles or tin and the pitch of your ceiling. (Pitched ceilings cannot have loose fill as it will shift) There are different products suitable for different uses.

Check with your contracter what type of insulation is the standard specification on your build. You may wish to upgrade it to a higher R rating or to a different product.

How roof insulation works- basically you are trying to prevent the hot air from your heater escaping through the roof/ceiling in winter and in summer to keep the hot air from outside and/or inside the roof from penetrating the ceiling and heating up your room. You can also insulate walls and floors but the roof (in double brick homes) accounts for the greatest percentage of heat transfer, around 30-40% and is therefore the most common and cost effective way of maintaining the required temperature. You need only insulate ceilings to livable rooms, eaves, garage and porch insulation is not necessary, you may wish to insulate the alfresco depending on how enclosed it will be.

When choosing a type of insulation think about

  • How easily you want to be able to handle it, many products require gloves
  • Can you or a tradesman easily replace the product to the correct thickness after completing work in the ceiling
  • Enviromental concerns, how friendly is the product.
  • Will the product compact over time
  • If the roof leaks will the product be damaged (or cause damage to the ceiling)
  • Confirm all downlights are protected with fire resistant enclosures
  • Keep in mind covering the ceiling joists with insulation creates a safety issue for anyone working in the roof space.

Download a PDF from theThe Insulation Council of Australia and New Zealand (ICANZ)

Types of insulation are listed below:

Loose Insulation

  • Cellulose Fibre  (mulched up newspaper)
  • Ganulated Rockwool
  • Wool
  • Polyester

Blow-in or loose insulation is normally the cheapest option in the category.

  • Loose insulation is blown into the roof and sits between the rafters.
  • As the insulation is loose it can cover the entire ceiling area with no gaps.
  • Some types of this insulation are inclined to settle over time.
  • Increasing the height of the fill increases the R code.

Loose fill can also be blown about in the roof space as it is loose in nature but you can request ‘sealing’ at the time of installation to overcome this. Remember if you have a roof leak some loose fill may absorb the moisture. In extreme cases the fill gets so heavy the ceiling caves in. Effective installation is the key to this insulation. The cover must be the correct thickness in all areas or the insulating qualities are compromised. To achieve high R codes the ceiling joists may need to be covered, this create a safety issue. High R codes can create a weight problem.

Bulk Insulation

Bulk insulation means that a mass of the product is placed in the roof space.There are the batts (a batt is a rectangular prefabricated insulation pad) and there are also the new types which look like a plastic pillow.  Insulation sits between the ceiling joists and creates a barrier to keep the internal temperature as desired. All R ratings are available. 

Sealed Cellulose Fibre

Cellulose Fibre is now available in a sealed plastic option not just a loose bulk fill. The sealed units look like small plump plastic ‘pillows’. These are totally contained and are waterproof, vermin proof and great for allergy sufferers.This solves the problem of the loose fill blowing about or absorbing moisture and means moving the insulation to access the ceiling is easy and requires no protective clothing. Easy and quick to install. Enviromentally friendly as manufactured from recycled materials.

Glasswool Batts / Fiberglass Batts

Fiberglass batts are light and flexible and easily installed by the homeowner or a professional, however remember to avoid contact with the fibres as they can make you very uncomfortable. Care should be taken during installation to avoid gaps between batts and joists, however downlights and fans will need to be protected from contact with the insulation. These batts also have acoustic qualities so work well with tin roofs. Bear in mind that if you need to go into your roof space at a later date you will need to avoid contact with the batts. Full range of R values available.


Rockwool is made from volcanic rock which is melted and then spun. Rockwool is available in batts as per fiberglass batts. Rockwool is denser than fiberglass and thus has greater insulating qualities than fiberglass both thermally and acoustically. It is usually more expensive than fiberglass but care should still be taken during installation as it is prickly like fiberglass. Rockwool is inherently fire resistant which has the added bonus of creating a fire blanket effect in your roof.

Polyester Batts

Polyester batts are similar to the abovementioned products but do not cause irritation during installation and are great for people with allergies. Polyester is the same product that pillows are made from. Insulation polyester can be spun from recycled plastic bottles. It is one of the least toxic insulation products available and has great acoustic qualities as well. R value is limited to 3.5


Wool is a natural product available in loosefill and in batts. Loose fill must be installed by an experienced contractor in order to attain the desired depth and R code. Both forms are treated to create a fire retardant and vermin resistant product, treatment to prevent rotting is also applied. Check your Wool insulation has been treated for all of the above before purchase. Wool is a lighter product than most others available in the market thus reducing the load weight in your ceiling. The great advantage of wool insulation is that it is an enviromentally friendly renewable resource

Reflective Foil Insulation

Reflective foil laminate insulation is laid under the roof; this foil has reflective qualities that provide some insulating value. This product comes in rolls and is laid directly beneath the roof cover. (But not touching there must be an air gap of 25mm or it doesn’t work) Its effectiveness lies in that the roof space itself doesn't heat up as much due to the protection being directly beneath the roof cover and the heat is reflected back out of the roof, there is also the added benefit of being a moisture and sound barrier. If your roof cover is compromised (a cracked tile) the rain will be temporarily prevented from penetrating into the roof space (you will still need to fix the roof tile before the cover is compromised). Without further ceiling insulation in winter your internal heat can still escape through the ceiling and sit in the roof space. If used in conjunction with ceiling insulation you have a very effective system.

Reflectice foil will also increase protection from airborne fire hazards in bush environments by creating an additional layer to prevent sparks igniting in the roof space.

Care must be taken during installation to ensure there are no rips or tears and that sufficient overlap is allowed for where joins occur. Foil insulation is compulsory in some coastal areas and or windy locations

Insulation is available in many different forms and prices, basically you need to ensure that the insulation you choose is fire resistant and resistant to vermin and insects. Any product complying with the Australian standards will have these attributes. You should also receive a guarantee for your purchase. 

Helpful hints

Choose the product that suits your budget; get the highest R code you can afford. If you have cathederal ceilings you will need a product that won't shift.

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Roof cover

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