How Do Fabric Ducts Reduce Draughts?

Insights

A ventilation system can be delivering the correct amount of air and still leave people uncomfortable. One of the most common reasons is velocity. If cooled air arrives too quickly and is concentrated in one area, people sitting or working beneath the outlet may feel a continuous cold draught.

Fabric ducting offers another way of distributing that same supply air. Rather than relying on a small number of grilles or diffusers, air can be released gradually along a much larger length of duct. This gives designers more control over where the air travels and how quickly it reaches the occupied part of the room.

 

Why Do Some Ventilation Systems Create Draughts?

A draught usually becomes noticeable when relatively fast-moving air reaches people directly. With traditional rigid ductwork, a large amount of air may leave through a limited number of ceiling grilles. If the outlet velocity is high or the grille is positioned directly above desks, seating or workstations, people nearby can feel considerably cooler than those elsewhere in the room.

Moving the thermostat may not solve the problem because the issue is often the way the air is being delivered. This can be particularly noticeable in offices, classrooms, restaurants and laboratories, where people spend long periods in roughly the same position.

 

How Does Fabric Ducting Spread Air More Evenly?

Fabric ducts can act as both the duct and the diffuser. Air travels through the textile duct and is released at multiple points along its length rather than being carried to a handful of separate outlets.

Prihoda systems can use precisely positioned perforations, micro-perforations, and fabric nozzles depending on the airflow required.

Spreading the supply air across a greater area can reduce locations where a strong jet of air is concentrated on one person or workstation.

It also helps address the opposite problem. If most of the conditioned air is entering one part of a room, other areas can receive too little. More even distribution can help reduce both obvious draughts and stagnant areas.

 

Why Are Micro-Perforations Useful for Reducing Draughts?

One of the most useful options for low-velocity distribution is micro-perforation. Prihoda uses laser-cut holes as small as 0.2mm, positioned in calculated patterns around the duct. These allow relatively high volumes of air to be released through a large number of tiny openings. (prihoda.co.uk)

The result can be a much gentler air movement than sending the same volume through a small conventional grille.

At the University of York laboratories, for example, Prihoda used bands of micro-perforations to provide low-velocity airflow that would avoid creating uncomfortable air movement and would not interfere with sensitive laboratory equipment.

 

Does the Position of the Holes Affect Comfort?

Fabric ducts are designed around the room rather than simply having identical holes all the way around them. Perforations can be positioned on particular parts of the duct so the air is directed where it is needed.

A seating area may require gentle air movement spread across a wide area. A warehouse may need warm air projected much further down from a high ceiling.

Prihoda’s Eden Project installation demonstrates how different outlet arrangements can even be used on the same system. Larger perforations delivered air towards one occupied area, while micro-perforations supplied a higher volume at lower velocity to staff working nearby. This is why the airflow pattern needs to be considered alongside the duct itself.

 

Can Fabric Ducts Reduce Draughts When Cooling a Room?

Cooling is where low-velocity distribution can be particularly useful because cold air falling directly onto people can quickly become uncomfortable. Fabric ducting can release cool air gently through micro-perforations, allowing it to mix with the surrounding room air before reaching occupants.

Displacement ventilation takes this approach further. Prihoda’s displacement systems can introduce large volumes of conditioned air at very low velocity. When cool air is supplied from high level, it can gradually fall into the occupied zone because it is denser than the warmer air around it. (prihoda.co.uk)

The aim is to achieve the required room conditions without people experiencing a noticeable blast of cold air.

 

Does Reducing Draughts Mean Reducing the Amount of Air Supplied?

Usually, no. The objective is to distribute the required air more effectively. A room may still need a substantial amount of ventilation or cooling. The difference is that this volume can be divided across hundreds or thousands of small openings instead of being concentrated through a few outlets.

Our airflow calculator can help to this distinction clear as it considers both air volume and velocity, warning when the velocity through a selected duct becomes too high.
Good comfort therefore depends on balancing the quantity of air with its speed and direction.

 

Why Does the Original Airflow Design Matter?

Fabric ducting will only reduce draughts effectively if the system is designed for the actual space. Designers need to know the required airflow, duct position, room dimensions and where people will normally be located. Heating and cooling requirements also matter because warm and cold air behave differently.

A classroom full of seated pupils requires a different airflow pattern from a warehouse where people are moving around beneath a ten-metre-high ceiling.

When these factors are considered at the design stage, fabric ducting provides considerable flexibility in controlling exactly where conditioned air enters the room and how quickly it gets there.

 

FAQs

Why Do Air Conditioning Systems Sometimes Feel Draughty?

Draughts can occur when conditioned air reaches occupants at too high a velocity or is concentrated through an outlet positioned directly above them.

 

What Are Micro-Perforations in Fabric Ducting?

Micro-perforations are very small laser-cut openings in the fabric. They allow air to be released gradually across a large area of the duct at relatively low velocity.

 

Can Fabric Ducting Still Move Large Volumes of Air?

Yes. A system can distribute substantial air volumes while using many small outlets to keep the air velocity reaching occupants relatively low.

 

Can Fabric Ducts Be Used for Both Heating and Cooling?

Yes. The outlet arrangement can be designed differently according to whether warm or cool air is being supplied and how far that air needs to travel.

 

Do Fabric Ducts Guarantee a Draught-Free Room?

No ventilation system can guarantee comfort in every circumstance. The airflow, room layout, duct position, temperature difference and occupancy all need to be considered as part of the design.