Fire rating of building products including insulation has been making headlines lately but, according to experts, simply focusing on picking non-combustible products is not the only – or even perhaps the best – solution.
Keith Anderson, Kingspan Insulation technical R&D and accreditations manager, says projects could be missing out on the benefits of innovative insulation products if they take the conventional deemed-to-satisfy route to meet the requirements of the National Construction Code instead of the more innovative Performance Pathway.
The DTS pathway, Anderson says, generally locks projects into using non-combustible insulations such as low-density fibreglass (LDF). However, some newer, alternative insulations such as polyisocyanurate (PIR) foams, phenolic foams and some high density fibreglass, which are deemed combustible, deliver a better energy performance.
Anderson says that closed-cell phenolic insulation, for example, is technically considered combustible, but performs exceptionally well when exposed to fire, and has almost double the thermal resistance of LDF for the same thickness.
A Performance Solution approach can allow use of these products while still achieving compliance, Anderson says.
An example might be to ensure that the insulation is encapsulated with non-combustible materials and that air can’t enter the cavity.
Anderson says it is crucial that a Performance Solution of wall assemblies represents exactly what will be constructed. It’s also vital to ensure the project is well constructed.
“That comes down to building control on site,” Anderson says. Routine inspection and supervision, particularly on a high rise project, and the quality of tradesmanship are all crucial.
In terms of ensuring air can’t enter the cavity, a blower door test may give an indication of air-tightness and how well-sealed the building lining is.
Another downside of the low-density materials is they can sag over time within wall cavities, reducing thermal performance even further. Others, while not combustible as such, can melt away in a fire event, leaving wall cavities exposed to higher temperatures for longer periods of time.
Anderson says specifiers, builders and verifiers should look for third party certification on any product. CodeMark, for example, is an assurance the manufacturer has quality control in place.
“All documents should identify the product clearly in the test reports and these reports should come from an accredited laboratory,” Anderson says. “These are two critical things the verifier and certifier should check.”
What the Fire Protection Association says
Chief technical officer and deputy chief executive of the Fire Protection Association Australia Matthew Wright says that in internal insulation applications, the concern is not only about the speed of spread of a fire, but also the toxic products of combustion.
He says, the National Institute of Science and Technology in the US has recently undertaken a study that found the speed of fire growth has reduced the time to flashover (the point at which all combustibles in a room have ignited and the room is untenable) from almost 30 minutes in the 1950s to three to four minutes in a room with modern furnishings containing plastics and other synthetic products.
“Smoke produced by many plastic and synthetic products is much higher in toxicity, affecting egress and tenability,” Wright says. “Fires with these materials often spread quicker which is why FPA Australia contends that all multi-storey residential buildings should be sprinkler protected.”
Wright says the key objectives of fire safety are to alert occupants to respond and contain fire spread to provide the greatest amount of time to leave safely and limit damage. Any product that threatens these objectives needs to be controlled or mitigated by design and installed and maintained systems and equipment.
Some of the mitigation elements a project’s fire engineer might employ include selecting a product that not only has high thermal performance but also tested fire performance.
“Some manufacturers produce product that performs well in fire conditions subject to installation configurations,” Wright says.
He says products can also be installed in limited locations, such as in areas that have reduced exposure to fire hazards and ignition sources; or installation requirements can be prescribed that prevent exposure of any combustible core material.
Neil Savery, general manager of the Australian Building Codes Board, says that under the NCC, a Performance Solution, previously known as an Alternative Solution, has to satisfy the approval authority that a product meets the performance requirements.
In each class two (multi-residential) building, insulation and cladding also have to meet the fire safety requirements in the NCC. An NCC Verification Method is being developed to include the new standard AS 5113 for fire testing of wall assemblies, which will assist in the verification of the relevant NCC Performance Requirements.
This standard, however, can be used now to demonstrate compliance with the NCC via a Performance Solution.
This standard provides a test methodology for demonstrating that any wall assembly – including cladding, insulation and the lining – that will be used at a height greater than two stories meets the fire safety requirements of the NCC.
Whether a project takes the DTS pathway or the Performance pathway, it will still need to engage a competent practitioner to verify a solution is fit for purpose.
In the case of a Performance Solution, more rigorous proof of acceptability will generally be required, as it is implicit in taking this pathway that a project involves a unique solution.
One of the positives of more projects taking the Performance pathway is they generally involve a degree of innovation.
Savery says that innovation is what drives positive change overall. These types of projects will often “lift the bar” above the minimum thermal and energy performance standards set by the building code, which being performance based provides scope for these innovations to become more mainstream.