A random survey of nine similar, commercially available insulated flexible duct products in Australia has found all samples failed to comply with mandatory energy efficiency performance standards.

Conducted as part of an industry report titled ‘A Survey of Thermal Performance of Flexible Duct’, the survey was commissioned by Insulation Australasia (IA) and conducted by Dr Cameron Chick from Acronem Consulting Australia. It sought to find out if the samples actually achieved their claimed thermal efficiency ratings of R1.0, the legislated national minimum requirement.

Insulated flexible ducts are used to channel conditioned air throughout buildings for heating or cooling purposes, with most consisting of an inner metalised plastic tube typically supported and strengthened by coiled wire, and covered by a bulk insulation material and outer protective sheath.

These ducts are commonly found in residential and commercial applications, and their efficient performance is considered vital – space heating in homes involving flexible ducts accounts for 38 per cent of all household energy consumption, a figure that is expected to continue increasing.

Moreover, thirty per cent of energy losses are through flexible ductwork.

However, tests on all nine of the ‘like’ samples carried out at CSIRO Infrastructure Technologies, Thermal Test laboratory revealed that they achieved an average R-value of just R0.763 (m2K/W) with a standard deviation of 0.10 (m2K/W). The products’ outer sheath, polyester thermal insulation material and inner core with metal wiring removed were assessed.

The best performing sample achieved R0.957 (m2K/W), and the worst R0.625 (m2K/W).

These poor results contravene the regulatory requirements of the National Construction Code, Building Code of Australia and Energy Efficiency provisions, which necessitate that insulation provided on ductwork shall comply with the requirements of AS/NZS 4859.1 Materials for the Thermal Insulation of Buildings.

“Due to the massive societal impacts of energy-wasting, non-compliant ducts, numerous governmental and regulatory bodies – including the Department of Climate Change – have shown an interest in the issue of non-compliant flexible ducts,” states a press statement by IA.

“The report also indicates an ‘expectation’ that the ACCC (Australian Competition & Consumer Commission) will scrutinise the sector on behalf of consumers.”

The report now calls for tighter monitoring and policing of product compliance, as well as reforms to the way products are assessed, with a shift to an ‘as installed’ performance assessment rather than the current process of assessing raw materials.

Read the full report here.

Geraldine Chua

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