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There are alternatives to galvanised steel ductwork, including lightweight products made from fabric and even cardboard.

Optimise system design

Ductwork is a major component of ventilation systems and is typically made of steel, which has a high embodied energy impact. If the aim is to improve resource efficiency, building design has to allow for the effective integration of the ductwork at the early stages. The constraints imposed by the building and the siting of fans, plant items and terminals can lead to an overall duct layout that is not ideal. Ductwork design should consider both strategic and detailed issues.

These include:

• Rationalising the area of the building that has to be mechanically ventilated and using natural systems where applicable
• Locating the air handling unit as close as possible to the ventilated space in order to minimise the length of the ductwork run
• Using local extraction by the appropriate location of plant to minimise duct runs
• Minimising the number of fittings possible to reduce embodied energy, materials use, cost and pressure loss
• Ensuring ductwork is sealed to minimise leakage – this allows reduction in both equipment and ductwork size
• Employing circular ductwork where space allows to cut the amount of material required
• Reducing unnecessary pressure drops in the system by carefully sizing, routing and detailing ductwork.

Alternative materials

There is the potential to use alternative materials for some building services components to reduce the lifecycle impacts. Of course, when considering alternative insulated ductwork materials, other design factors need to be considered, such as acoustics and fire rating.

In particular, there are alternatives to galvanised steel ductwork, including lightweight products made from fabric and even cardboard.

Fabric ductwork can be applied in a range of buildings, including swimming pools, laboratories, classrooms and offices. It comprises considerably less material, and therefore less embodied energy impact than metal ductwork.

For example, fabric is less than 10% of the weight of the galvanised steel per unit of surface area.

Tri-wall cardboard ductwork has been developed, which has a coating made from a water-based solution with a water dispersal polymer, fire-retardant minerals and a final hydrophobic finish.

The coating can be recycled with other water- and oil-based printed paper. The cardboard is high strength and can be recycled into other substantial products.

Additional benefits of cardboard ductwork include the need for less insulation than steel ductwork, as it has some insulating properties. The weight of the cardboard ductwork is 1.95kg/m2 surface area – approximately 20% of the average weight of galvanised steel.

It is roughly the same percentage in terms of embodied energy, although this is harder to calculate until a life-cycle analysis is completed. Lightweight ductwork cuts transport costs and emissions, and those that can be flatpacked have an even smaller environmental impact.

Of course, using different materials for ductwork could increase the pressure drop of the system. Therefore, any decisions about using alternative materials have to be informed by a simple life cycle assessment to ensure that reducing embodied energy impacts does not have an adverse effect on the operational performance.

GatorDuct is the future of fire rated ducting with its innovative HVAC technology. For more information, call us on 0844 846 0357 today.