CPD PROGRAMME | DUCTWORK remark that in common with many building products, there is little published work on the end of life stage of phenolic foam (which, in the context of their paper, is referring particularly to external wall insulation systems), and owing to the layered nature of the systems and the use of adhesives and tapes it would be likely that any phenolic foam ductwork system removed at end of life would be viewed as contaminated. As such, it would likely be sent to landfill, although it could be incinerated with energy recovery. It is noted that the importance of developing strategies for effective removal and disposal of such systems might best be taken into account during system development. The relevant UK/European standard for the basic requirements and characteristics for ductwork made of insulation boards and used in ventilation and air conditioning systems of buildings (for human occupancy) is BS EN 13403:2003.5 The core requirements of the standard are summarised in Table 1. Independent tests6 on a sample of a commercially available phenolic foam ductwork system indicate that the material and the fabrication method, as shown in a simplified form for a straight duct in Figure 6, produces ductwork that has integrity class C. The US Underwriters List (UL) standards are often referred to when considering specifications for ductwork. UL 181 is an American National Standards Institution (ANSI) recognised standard for factory made ducts and connectors, which was most recently updated in 2021 the standard may be viewed at no cost on the UL website.7 The standard provides a range of performance tests that cover similar areas to BS EN 13403, which in summary includes: testing for flame penetration and burning, and flame resistance (for jointing materials); corrosion resistance; and mould growth as well as tests on the structural integrity (including impact, puncturing, sagging, torsion and collapse) and stability under various temperature and humidity conditions. Ductwork systems that comply with the requirements of UL 181 are listed on the UL website bit.ly/CJFeb22CPD1 A comparative embodied carbon analysis8 was undertaken to illustrate the relative embodied carbon of an example length of phenolic circular ductwork compared with an equivalently dimensioned spirally wound galvanised steel duct. Although not a comparison of EPDs as defined by BS EN 15804, this was undertaken in line with the criteria from that standard for life-cycle stages A1 to A4. The comparison was based on a 10-metre length of 250mm nominal diameter ductwork including duct hangers, jointing and taping, with similar levels of insulation Figure 1: Information for a life-cycle assessment as defined by BS EN 15978:2011, including typical system boundaries (Source TM652) and vapour protection. This study did not include a consideration of the typically uncertain section C end of life and section D beyond end life, but as shown in a summary of the findings in Figure 1, it indicates that the phenolic foam ductwork system had the significantly lower embodied carbon equivalent of the two. A whole-life cost exercise (excluding operational energy use) was undertaken,9 comparing a ductwork system fabricated from a phenolic foam and one of mineral fibre insulated galvanised steel ductwork. It indicated a reduction in total cost (in the order of 20% for an installation of capital cost circa 175k) across the range of ductwork sizes in a low-pressure ductwork system. The report indicates that the Figure 2: Comparative embodied carbon study of phenolic foam duct (including duct supports and hanger systems) and standard metal ductwork plus insulation (including duct supports and hanger systems). EN 15804 System Boundary: Stages A1-A3 Product, Module A4 Transport (Source: Hilson Moran8) 50 February 2022 www.cibsejournal.com CIBSE Feb22 pp49-52 CPD 191.indd 50 28/01/2022 16:25