Insulated flexible duct survey: all samples non-compliant

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

The survey was conducted as part of an industry report titled ‘A Survey of Thermal Performance of Flexible Duct’, commissioned by the peak body Insulation Australasia (IA) Ltd.

Insulated flexible ducts are used to channel conditioned air throughout buildings for heating or cooling purposes. Most flexible ducts consist of an inner metalised plastic tube, typically supported and strengthened by coiled wire, covered by a bulk insulation material and outer protective sheath. These ducts are commonly found in residential and commercial buildings, and their efficient performance is vital – space heating in homes involving flexible ducts accounts for 38 percent of all household energy consumption.

The report involved a scientific analysis of nine ‘like’ samples of insulated flexible duct products with claimed thermal efficiency ratings (R-values) of R1.0, which is the legislated national minimum requirement.

The tests

Testing was conducted at CSIRO Infrastructure Technologies, Thermal Test laboratory. It involved careful assessment of the outer sheath, polyester thermal insulation material and the inner core (with metal wiring removed), using approved examination techniques.

Results demonstrated an average R-value of just R0.763 (m2K/W) with a standard deviation of 0.10 (m2K/W), significantly below the claimed targets of R1.0.

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

These uniformly poor results, according to the report, are disappointing and clearly contravene the regulatory requirements of the National Construction Code, Building Code of Australia (NCC, BCA), 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.

The impacts

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. The report also indicates an ‘expectation’ that the Australian Competition and Consumer Commission will scrutinise the sector on behalf of consumers.

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

IA director Warrick Batt has welcomed the findings of the report, calling on all manufacturers and installers to be aware of the consequences of allowing non-compliant product to enter the market. “Whenever poor quality or non-compliant product is used, the entire sector is tarnished. Low standards adopted by rogue operators diminish the credibility of reputable manufacturers, undermine price points, and threaten ongoing research and product development.”

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