How to choose insulation products that offer good thermal efficiency while mitigating fire risks

In our last article, we discussed whether current measures regulating fire protection in Australia are enough. In this feature, we look at the role product manufacturers play in ensuring the built landscape is fire safe, with a specific focus on insulation, a typically flammable material.

Understanding and complying with the fire protection requirements of the Building Code of Australia (BCA) and liaising with fire safety engineers early on in the design process is only half the battle won for ensuring structures are fire safe and resistant.

Specifying the right products, materials and systems, which are also regulated and must be proven to perform well in a range of areas such as flammability, flame spread and fire resistance, is the other half.

A good example of this fine balance is insulation, a product regularly used by architects to improve the performance and efficiency of buildings despite being a potentially highly flammable material. According to the Australian Competition and Consumer Commission (ACCC), 5.9 per cent of roof fires in Australia from 1999 to 2004 reported insulation as the first material ignited.

Product Review: four high performing insulation products that are tested and proven to be fire resistant

However Nathan White, fire safety engineer team leader at the CSIRO, points out that it is never a ‘silver bullet’ answer of whether a product or material such as insulation is safe or not.

“You can get different types of core materials, which have varying levels of performance, but one of the more important factors is how the material is actually assembled and constructed. If they are built in a way where the seams won’t open up and don’t fail structurally to expose the core on the inside (e.g. having a metal skin on the outside), then they actually perform quite well,” says White.

The context in which a product is utilised is also an important consideration. For instance, a sprinkler protected cold storage building which utilises insulated sandwich panels has low risk levels due to the high reliability of the sprinklers.

Insulation materials

According to Peter Ruz, national marketing manager at CSR Bradford, the flammability of a product depends on its level of organic content, with inorganic materials generally less flammable. 

Cellulose insulation. Image: commons.wikimedia.org

A popular insulation product around the world and previously in Australia is cellulose insulation, which has a reputation of being environmentally friendly. Made from 70-80 per cent recycled paper that would otherwise end up in landfill and utilising very little energy to be produced, it is naturally flammable but when treated with fire and pest retardants, borax and boric acid, its ignition potential is reduced.

Polyester insulation, made out of polyester fibres including recycled plastic bottles, is another material favoured by architects and building designers. More expensive than fibreglass insulation, polyester is a fire resistant material, and requires relatively high temperatures to burn. It offers both heating and cooling properties, is not affected by moisture, and does not shrink.

Fibreglass/glasswool insulation is one of the most popular insulation materials used in Australia's residential market today. Manufactured out of up to 70 per cent recycled glass, it involves melting the raw materials, glass and sand at temperatures around 1550°C. It is generally easy to install and cheap, and one of the most resistant materials to fire.

A relatively new product in Australia, earthwool insulation is made from inorganic glass fibres bonded by a binder created with renewable bio-based materials rather than traditional petroleum-based binders. It contains no phenol, formaldehyde, acrylics or artificial colours found in glasswool, and is also resistant to fire.

Earthwool Batt from Knauf

Mineral wool insulation (also commonly called 'rock wool' in Australia) is made from volcanic rock melted at high temperatures and spun into a mat or batt of fine fibres. It typically only burns at high temperatures, often in excess of 850°C, and acts as a fire barrier for roof, walls or floors. However, there are some mineral wool products available in Australia that are designed for lower temperature applications. 

While these products do not present immediate hazards, fires can still occur particularly if poor installation is carried out, such as near halogen down lights and fans that have not been adequately covered. Installation is regulated under AS 3999.

Blown fibreglass. Image: Green Oak

Back to the rule book

In Australia, it is expected that insulation products do not present a fire risk as long as they are tested and proven to meet the minimum requirements of the National Construction Code (NCC). According to Rob Jones, Market & Development Manager of Autex, fire protection requirements in the code will:

• Safe-guard people from illness, injury and possibly death in the event of a fire while in the building and/or evacuating the building.
• Facilitate the activities of emergency services personnel.
• Prevent the spread of flame between buildings and protecting other properties from physical damage caused by the failure of a building structure as a result of fire.

The Fire Resistance Level (FRL) will test the complete system’s performance including linings, framing and insulation materials. The AS 1530 Part 4 fire test failure criteria include:

• Structural adequacy – a measure of a tested assembly to be load bearing during fire conditions 
• Integrity – a measure of a test assembly to restrict the passage of flames and hot gases
• Insulation – a measure of the temperature rise on the non exposed side of a fire-resistant separating barrier

The FRL is expressed as structural adequacy/integrity/insulation. For example:

Australian Standards AS1530.3 also provides the Early Fire Hazard indices for four key attributes: Ignitability Spread of flame, Smoke developed and Heat evolved.

However, Ruz explains that there is no PASS/FAIL for this standard, rendering claims that products meet these requirements “meaningless”. Instead, he says AS1530.1, a pass/fail test where products are classified as either combustible or non-combustible, is more helpful.

In contrast, Jones points out that the combustibility test is called up for limited construction types, and that the best tests are those that replicate site conditions.

“The temperature of this [combustibility] test is in the region of 750°C. Common products such as plasterboard, fibre cement and sheet metals cannot pass this test but are considered exempt, effectively rendering this method as irrelevant," says Jones.

“AS1530.1 also declares that glass and rock wool insulation materials of similar density and calorific values which should yield similar results have demonstrated differing outcomes when tested and may not be relevant. Regulating authorities can choose not to use this information.”

Kingspan Insulation’s technical manager Keith Anderson adds that if the insulation also serves as the internal wall or ceiling lining, specifiers should look at clause 4 of Specification C1.10, which provides the testing requirements to determine the Group Number for the material.

“When the insulation also serves as the internal lining, the requirement becomes more stringent for critical areas such as along evacuation routes. These areas would typically require Group 1 materials, which need to be tested for a full 20 minutes in the AS ISO 9705 test room without flashing over,” Anderson says.

The AS ISO 9705 test method refers to the use of a 300kW burner in the corner of the test room for the last 10 minutes. Flashover is defined by the NCC as the point where the total heat release rate generated in this test is 1,000 kW.

The following materials are required to be tested to ISO9705 to obtain a valid result:

• All assemblies, including those with profiled facings; this is any combination of products sold as a finished unit i.e. aluminium / steel sandwich panel,any forms of structural insulated panel, fixed pin-boards.
• Materials or assemblies that melt or shrink away from a flame; PET Panels, polystyrene and polyester insulation materials). 
• Assemblies with joints and openings; and perforated ply, wooden panelling
• Products with a reflective surface. Foil faced materials including insulation including foil faced glass wool insulation materials and laminated panel products.

“When insulation materials are tested in accordance with the NCC and specified appropriately for their application and location in the building then they are all ‘fire safe’,” says Anderson. However, he warns that while most products will meet these requirements, there is a danger that some do not, especially if they are products imported by a reseller. It is also inadequate to test under international test methods which are not called up in the NCC.

He goes on to advise architects that the products they specify should be supplied by a reputable company with third party Quality Assurance accreditation. Products that are CodeMark accredited provide further assurance that the product is fit for purpose.

“A full specification of the product by name followed up with adequate site supervision helps to ensure that the product is not substituted on site with an inferior product. Remembering that there may have been several reasons why the specified product was chosen is also important – besides the R-value it may have been also about the thickness, fire performance, durability, compressive strength and more,” Anderson concludes.

Correct installation

Most ‘fire safe’ insulation products may also present risks if poor installation is carried out, such as near halogen down lights and fans that have not been adequately covered. Minimum insulation clearances around un-rated downlights are required for all types of insulation.

Test methods that certify if insulations are suitable for use with down lights have already been adopted in other countries, and are currently being considered in Australia. According to Jones, insulation materials must be classified non-flammable in accordance with the requirements of IEC60695-11-05.

“Specify and use only IC / CA-Rated luminaires with thermostat protection to reduce or eliminate the requirements for clearances. This will not only provide a safer system but improve energy efficiency,” he advises.  

Lead image: Alamy. Source: The Guardian