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Retrofit Wall Insulation (Cavity Wall)

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WHAT IS CAVITY WALL INSULATION - Retrofit Wall Insulation ?

Blow in Wall Insulationwallinsul2

If your existing home has double brick or brick veneer walls, there is a cavity between the external brickwork and the internal brickwork/timber frame which can be used to install insulation. However, concrete walls, wood cavity walls (usually fibro cladded), weatherboard walls, and most other forms of walling either have negligible internal cavities or cavities that are difficult or dangerous to access to the point where retrofitting cavity wall insulation would be costly or dangerous. In these cases, it is inadvisable to retrofit cavity wall insulation, but insulative cladding (such as polystyrene boards) can be added to the exterior of the walls. A weatherboard wall can also be insulated either by prising off boards to gain access to the gaps between the studs and then replacing them afterwards or by drilling holes through the internal walls (through the plaster)

How many houses has Just Rite installed cavity wall insulation?

Just Rite pioneered cavity wall insulation in Australia and has installed cavity wall insulation in more than 25000 houses in Canberra, Sydney, Blue Mountains, Melbourne, Bendigo, Orange and Bathurst since 1987.

Saint Gobain ISOVER InsulSafe33 Cavity Wall Insulation - Superior Glasswool 

Product Description

Loose-fill white glass wool, made with recycled glass, without thermo-hardening resin. Isover Insulsafe33 is compressed in bags and has to be blown mechanically. 


Thermal and acoustic insulation by blowing:

  • Cavity Wall
  • Attic Floors


  • Thermal and acoustic Insulation
  • Non- combustible
  • Mechanical Stability (Negligible settlement)
  • Durability (no rot and no mould growth)
  • Application comfort (few dust during blowing operations)
  • Lightness
  • Easy transportation (high compression ratio inside bags)
  • Fast application
  • Compatible with most of blowing machines

Technical Performance 


Performance Chart

The Following chat shows performance(R Value) for cavity walls 


Bradford Cavity Wall Insulation- Rock Wool

Bradford Cavity Wall Insulation is a specially treated water-repellent Rockwool. Rockwool is an insulation made of molten rock. It provides excellent thermal and acoustic insulation. The water-repellent Rockwool has been tested by BRANZ (an independent test laboratory). This test showed the cavity wall insulation did not transmit moisture. It has been approved by the Building Regulations Advisory Committee for use in brick veneer and double brick veneer walls. 
Test certificate No. V03/05.

Product Description 

Bradford Cavity Wall Insulation is a granulated inorganic mineral wool used to insulate external wall cavities in residential buildings. It is manufactured from Rockwool, which is made from a naturally occurring mixture of molten volcanic rock (usually basalt). It is spun into a matt of fine fibres and then granulated. The product is chemically stable, water repellent, rot proof, odourless and will not sustain vermin or fungal growth. The granulated Rockwool is applied through licensed installers through either blowing through holes drilled in the brick mortar (which are then re-sealed) or by lifting roof tiles to obtain access to the wall cavity. 


Bradford Cavity Wall Insulation has special hydrophobic additives which make it water repellent. This makes the product ideal for the insulation of cavity walls in domestic residences. The product also offers strong acoustic and fire retardant benefits. The insulation of cavity walls will improve the thermal performance of the house in hot and particularly cold climates, making it warmer in winter and cooler in summer. Bradford Cavity Wall Insulation is ideally suited to the insulation of already existing brick veneer and double brick residences. Bradford Cavity Wall Insulation can not only improve interior comfort levels, but reduces heating and cooling costs, and is an environmentally friendly product, both in its manufacture and use. 

Thermal Performance 

What is the R-value of double brick cavity wall? Bradford Cavity Wall Insulation has a thermal conductivity of 0.0443 Wm -1 K -1 at 23°C mean when applied at a recommended nominal density of 40 kgm -3 . For residential premises, the improvement in insulation performance is indicated below, for a nominal 50mm cavity. Filled cavities which are greater than 50mm offer greater performance. the table below the R values for walls after and before insulation. 

Building Construction  R-Value (no insulation)  R-Value (with insulation)
Brick veneer (no wall sarking) 0.46 3.4
Brick veneer (with sarking)  1.08  2.07
Double brick cavity  0.54  1.53


Bradford Cavity Wall Insulation will not deteriorate with age or settle and will remain effective for the life of the building, The product has no affect on the structural integrity of the building, and will not adversely affect wood, brick, wall ties or PVC electrical cables.

Moisture Resistance

Bradford Cavity Wall Insulation repels water, will not absorb or retain water, and will not transmit water across cavities. It will not affect the performance of damp-proof courses. The product does, however, have virtually no resistance to vapour transport, so air vapour can pass freely through the thickness, allowing the wall to breathe. This product assists in preventing condensation in the cavity.

Acoustic Performance

The following table details the acoustic performance of Bradford cavity wall insulation. 

  Without insulation With insulation
Brick veneer 50mm cavity 51 57
No wall wrap case (effective 120mm case) 51 59
50mm cavity  53 54-55 (56-58 with resilient ties)

Fire Resistance 

When tested in accordance with AS1530 Part 3-1999, Bradford Cavity Wall Insulation has the following
fire indices:

Ignitability  0
Spread of Flame 0
Head Evolved 0
Smoke Developed 0-1

Bradford Cavity Wall Insulation will not affect the fire rating of the existing wall construction. It will actually retard the spread of flame. It does not constitute a toxic hazard in fire conditions.

Supafil® 40 Cavity Wall Insulation For cavity walls - Glass wool (Only recommended for Double-brick walls)


Supafil® 40 Cavity Wall Insulation is an unbonded, non-combustible glass mineral wool insulation which requires no mixing on site.


Supafil® 40 Cavity Wall Insulation represents no known threat to the environment and has zero Ozone Depletion Potential and zero Global Warming Potential. 

Moisture resistance

Tests by the British Board of Agrément confirm that Supafil® 40 Cavity Wall Insulation will not transmit water to the inner leaf. Nor will it transmit moisture by capillary action across the cavity or from below damp proof course level. This has been confirmed by independent research conducted for the Energy Saving Trust which shows that cavity wall insulation does not add to the risk of water penetration.

Vapour resistivity 

Supafil® 40 Cavity Wall Insulation offers negligible resistance to the passage of water vapour and has a water vapour resistivity of 5.00 MN.s.g.m.

Handling and storage

Supafil® 40 Cavity Wall Insulation is supplied in polythene packs which are designed for short-term protection only. For longer term protection on site, the product should either be stored indoors or under cover and off the ground. Supafil® 40 Cavity Wall Insulation should not be left permanently exposed to the elements.

Typical U-values (W/m2K) for masonry cavity walls insulated with Supafil 40 Cavity Wall Insulation

Insulation thickness Brick outer leaf/cavity/100mm block inner leaf type: (mm) Dense block, (l= 1.13)

Insulation thickness U Value
100 0.33
50 0.55

All dimensions are nominal
*All U-values calculated with 12.50mm plasterboard (0.210W/mK) on dabs as the internal finish.
Acoustic Reports for Supafill is given separately under its own heading.


A special high performance blowing machine is used to pump the insulation into existing brick veneer walls.

Access to the cavity is gained by lifting a tile over the cavity and dropping a special hose to the bottom of the cavity. The hose is gradually lifted as the cavity fills.

Inaccessible cavities can be reached by drilling a 25 mm hole through the mortar joint and using a special cone to pump the Rockwool in through this hole. The hole is then remortared closely matching the mortar colour.


Between 25 - 35% of all heat loss is through the walls even if your ceiling is adequately insulated. By installing Bradford Cavity Wall Insulation you can stop about 85% of this heat loss or gain through your walls.


Did you know a double brick wall losses and gains almost as much heat as a brick veneer wall? The only difference is the lag time in this process. The R rating (Thermal Resistance) of a double brick wall is R0.45 compared with R0.4 for brick veneer.

An insulated double brick wall will perform better in winter because heat stored in the inner layer of brick will not be lost to the outside once the wall is filled with Bradford Cavity Wall Insulation. The reverse is true in summer.


Bradford Cavity Wall Insulation will increase the ENERGY EFFICIENCY RATING of your home in most cases by one star. It adds considerable value to your home, especially for resale purposes.


Be more comfortable all year round.

In Winter

Insulation reduces heat loss, keeping your home warmer.

In Summer

Insulation reduces heat entering through the walls, keeping your home cooler.

Save Money

Wall insulation makes heating and cooling much more efficient - your energy bill with ceiling and wall insulation can be cut by up to 30-50% so the insulation soon pays for itself.

Save the Environment

Reducing energy consumption cuts down on the emission of carbon dioxide greenhouse gasses - a responsibility for us all.

Noise Control

Wall insulation is a good acoustic insulation and will reduce noise entering the home from the outside. Cavity Wall Insulation increases the sound reduction in brick veneer walls from Rw51 to Rw59.

Fire Safe

Cavity Wall Insulation will not burn and actually retards the spread of flame. Cavity wall insulation has a 4- zero fire rating - when tested under Australian Standard 1530 Part 3 - m1976. This is the best possible rating.

Condensation Control

Bradford Cavity Wall Insulation will reduce or eliminate condensation on internal walls. No condensation means no mould and less frequent repainting of internal walls.

We are so confident Bradford Cavity Wall Insulation will be effective and long lasting that we give you a written guarantee for 100 years!

Bradford Cavity Wall Insulation is guaranteed to be resistant to the movement of water from the outer to the inner leaves of the wall and will not settle, shrink or decay.

Click here to download our Fact Sheet