What is ductwork?

Ducts or ductwork are connecting tubes or pipes that normally form part of systems like ventilation system, moving air through a building. An example we would all be familiar with is a chimney on a fireplace which is used to transfer smoke from the fire to the outside air. Pipes used to transfer gas or water are not considered as part of ductwork.

Designing a ductwork system involves a great deal of planning, detailing and sizing and is often one of the first things to be considered when designing a building. This is because of its huge importance in the use and effectiveness of that building and the need to integrate the duct routes with other parts of the main design. The routing of ductwork can become quite complex, especially when the ductwork passes through various elements of a building.

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Ducts can be made from a variety of different materials. The most common material is a type of galvanised steel which has a zinc coating to stop rust from forming. Aluminium is another popular choice as it is fast to install and lightweight. It’s a good material for moulding into custom shapes too.

Ducts can also be fabricated from polyurethane and phenolic foam sheets that have an aluminium face on each side. Fibreglass is also used for ducting as it offers good thermal insulation and absorption of sound. A flex duct can be made from flexible plastic covering a metal wire coil. For quality parts for extraction systems, like a Spiral Duct, visit Dust Spares

Planning the layout of ductwork can become very complex indeed as it will involve numerous supply and return ducting that branch out to many different parts of a building. For example, a heating ventilation and air conditioning system (HVAC) will have ductwork running through different voids in a suspended ceiling. These routes supply and extract air from the rooms below through diffusing grilles. Whether the air is removed or supplied will depend on the direction of the fans or an air control unit. The size of the required ducts are worked out based on the relations between air velocity, size, resistance and air volume.

Whether it’s an HVAC unit or an exhaust system for keeping air clear of pollutants, systems that handle air can be noisy and vibrate, causing distraction. This is made worse when ductwork passes between spaces that are acoustically separate. To combat this problem, acoustic attenuators can be installed inside the ductwork or unit. Issues with vibration can also be helped with insertion of various flexible sections between the air handling unit and the ducting. Also by isolating the HVAC unit from the building.

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Other parts that can be included not a ducting system include:

Boxes that redistribute and redirect airflow according to needs

Movable parts to allow a small section of the main duct to be diverted into one of the branch ducts.

Dampers to control volume levels, allowing air flow adjustment manually or automatically.

Points of access for cleaning and maintenance.

Fire and smoke dampers.

Where direction changes occur, turning vanes can be installed to minimise resistance or turbulence caused and guide the air.

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