Building services can make up a significant proportion of the cost of constructing, operating and maintaining a building throughout its lifespan. When specifying these systems, it’s now more important than ever to consider how modern construction methods can help to deliver improved value. Recent research from Rider Levett Bucknall has highlighted that by fitting pre-insulated phenolic ductwork instead of traditional sheet metal ductwork, it is possible to achieve a 22% reduction in installed costs and whole life cost savings exceeding 51%.
Pre-insulated ductwork is fabricated from rigid phenolic insulation panels with a foil facing. This design eliminates the lagging stage and means the ductwork can be installed flush to ceilings, floors or walls – saving space. Sections can also simply be modified on site with standard hand tools, ensuring that any unexpected changes to the building layout can be easily handled.
In practice, the pre-insulated phenolic ductwork can be as much as 75% lighter than a comparative sheet metal system with mineral fibre lagging. In addition to reducing structural support requirements, this means it is possible to join several sections of ductwork together at floor level (up to 15 meters in length) and lift and fit them in a single operation – further speeding up installations.
The fabricated ductwork sections can also offer excellent performance characteristics, with systems capable of meeting air–leakage Class C and D both at low and medium pressures (ref. BS EN 1507: 2006; BS EN 13403: 2003 and BESA DW/144). This airtight design can allow the desired air flow rates to be met with smaller, more efficient fans, potentially significantly lowering long-term energy demand.
Upfront cost savings
Rider Levett Bucknall carried out a detailed cost analysis to assess how the use of pre-insulated phenolic ductwork could affect installed cost when compared with insulated galvanised steel ductwork.
For this, they consulted with a number of suppliers and installers, providing each with a standardised duct layout featuring a number of different duct dimensions and components, including straight sections, 45 and 90 degree bends and tapers. The firms were then asked to provide supply and installation costings for two comparative specifications of the different ductwork systems:
1. Pre-insulated phenolic ductwork manufactured using 22 mm thick panels vs galvanised steel ductwork with 40 mm mineral fibre
2. Pre-insulated phenolic ductwork manufactured using 30 mm thick panels vs galvanised steel ductwork with 50 mm mineral fibre
The results showed that based on the averaged quotations supplied for both scenarios, significant savings could be achieved with pre-insulated phenolic ductwork. In the first scenario, it was possible to achieve average cost savings of £3,735.16, a reduction of 21.8%. The savings were even greater in the second scenario with estimated costs falling by over £4,012 (22%).
Whole life savings
Rider Levett Bucknall also carried out additional analysis looking at the cost of maintaining and adapting ductwork across its whole life. Pre-insulated phenolic ductwork can typically be cleaned with a mechanical rotary brush, with polypropylene fibres and a plastic ball tip, at a speed of up to 900 RPM. It is also much simpler to make adjustments once in-situ, such as adding access hatches. The Rider Levett Bucknall analysis assumed that changes and adaptations to pre-insulated ductwork would therefore be less costly over time and that the ductwork was less likely to be damaged during routine maintenance.
The research suggested that the cost of maintaining the pre-insulated ductwork with 22 mm thick phenolic panels would be less than half that of the galvanised steel ductwork (£3,000 vs £6,190), whilst savings of 48% could be achieved on the pre-insulated phenolic ductwork manufactured from 30 mm thick panels over the alternative galvanised steel system.
This research did not consider the impact of the specification on energy demand and operational costs. Depending on the operational parameters for the ventilation system, the enhanced airtightness which some pre-insulated phenolic ductwork systems can achieve could allow considerable savings to be achieved in both areas.
The global pandemic has placed additional pressure on specifiers to identify savings on each project. The Rider Levett Bucknall research shows that by utilising modern approaches such as pre-insulated phenolic ductwork, it is possible to reduce both upfront and long-term costs without compromising on building performance or quality.