Insulated Ducting

Insulated ducting provides superior thermal performance, reduces condensation, and helps maintain efficient airflow in commercial and residential ventilation systems. Available in standard and bespoke sizes, our insulated ducting is ideal for offices, warehouses, and industrial facilities. 

Designed for easy installation, it can be paired with our aluminium ducting for complete HVAC solutions.

All Ducting / Flexible Ducting / MVHR Units

What is insulated ducting used for?

Insulated ducting is used anywhere the duct surface would otherwise drop below the dew point of the air inside, causing condensation, or anywhere fan noise needs to be reduced before it reaches the occupied space. The main applications are MVHR supply and extract runs passing through unheated lofts or external walls, kitchen extract through cold ceiling voids, bathroom and utility extract in cold roof spaces, and acoustic attenuation on noisy inline or centrifugal fans. Uninsulated ducting carrying warm moist air through a cold void will condense and drip — insulated ducting prevents this by keeping the outer surface warmer and the inner air above dew point.

Does insulated ducting stop condensation?

Yes — that's one of the two primary reasons to use it. Condensation forms when warm humid air cools below its dew point on a cold surface. In a cold loft or external-wall duct run, the outer duct surface drops close to ambient temperature. Moisture in the airstream condenses on the cold inner wall, trickles back down the duct and drips into the room or fan housing. Wrapping the duct in 25mm of glass wool insulation keeps the inner duct warmer, keeps the airstream above dew point, and prevents condensation from forming. It's essential for any MVHR or extract run passing through an unheated space.

Is insulated ducting worth it?

For MVHR, kitchen extract in cold lofts, and bathroom extract routed through unheated voids — yes, it's effectively mandatory. The cost of insulated ducting is minor compared with the disruption of ripping out a condensation-damaged install and replacing it. It's also worth it wherever a fan is mounted close to the occupied space (in-line fans above a false ceiling, centrifugal fans above a bathroom) because the insulation cuts the fan noise transmitting down the duct. For short warm-void runs where condensation risk is low and noise isn't a factor, standard uninsulated aluminium or combi ducting is fine and cheaper.

Should extractor fan ducting be insulated?

Insulate it whenever the duct run passes through an unheated space (cold loft, external wall cavity, unheated roof void) or whenever the fan is loud enough to be a nuisance. Short runs in warm internal voids don't need insulating. For a typical bathroom fan running straight out through an external wall, insulated ducting isn't strictly required. For a bathroom or kitchen fan ducted through a cold loft to a soffit or roof terminal, insulated ducting should be standard specification to prevent condensation dripping back down the run.

What sizes of insulated ducting do you stock?

We stock Systemair flexible insulated aluminium ducting in 127mm, 152mm and 203mm diameters, all in 10m lengths. 127mm suits MVHR and cooker hood extract on smaller systems. 152mm covers larger kitchen extracts, whole-house MVHR and higher-flow commercial bathroom extract. 203mm is used on larger commercial extract and supply runs. Other sizes (100mm, 125mm, 315mm, 400mm) can usually be ordered to stock on request — contact us with your diameter and quantity for availability and pricing.

When should I use insulated ducting vs standard flexible ducting?

Use insulated ducting any time the run passes through a space cooler than the air inside the duct (typically below 15°C ambient) or whenever you need to reduce fan noise transmission. Use standard uninsulated flexible ducting for short runs in warm internal voids where condensation isn't a concern. As a general rule for MVHR: insulated for any run in a loft, unheated garage, or outside the thermal envelope; standard aluminium for internal routes. For kitchen and bathroom extract: insulated wherever the duct enters a cold roof space.

Can insulated ducting reduce fan noise?

Yes. The glass wool jacket absorbs sound energy travelling down the duct wall, which is often the dominant noise path from an inline fan or cooker hood motor back into the occupied room. Typical noise reduction is in the 5–15 dB range depending on duct length, diameter and frequency — useful when the fan unit itself is close to the room or when the grille or diffuser acts as a sound path. For more aggressive attenuation, add an inline silencer in series with the insulated ducting; the combination gives dramatic noise reduction on quiet installations such as bedrooms and home offices.

How do I install and join insulated ducting?

Strip back the outer insulation jacket at each end to expose about 100mm of inner aluminium duct. Push the inner duct over the spigot of the fan, rigid duct or terminal and secure with a worm-drive hose clamp. Pull the insulation jacket back over the joint and tape over with foil tape to restore a continuous thermal envelope — if the insulation is left open at the joint, you'll get condensation at that point defeating the purpose. Pull the main run taut (don't leave slack), support horizontal runs with banding every 600mm, and avoid tight bends that crush the insulation.

How to choose the right insulated ducting

When specifying insulated ducting, consider the insulation thickness, duct diameter, and airflow requirements to ensure optimal performance. Choose materials that match the environmental conditions, such as high humidity or temperature fluctuations, and confirm compatibility with your existing HVAC system. 

Selecting the correct ducting reduces energy consumption and ensures efficient, quiet airflow throughout the system.

Applications for insulated ducting

This type of ducting is ideal for a wide range of HVAC systems, including commercial, industrial, and residential installations. It’s commonly used in environments where temperature control and condensation prevention are critical, such as warehouses, kitchens, and office spaces.

For projects requiring a complete solution, our insulated ducting works seamlessly alongside standard aluminium and metal ducting from our main ducting range.

Benefits of insulated ducting

Insulated ducting helps maintain consistent air temperature, reduces heat loss, and prevents condensation within ventilation systems. It also minimises noise from airflow, improving comfort in offices, industrial facilities, and commercial buildings. 

Using insulated ducting can enhance energy efficiency, reduce operational costs, and protect building interiors from moisture damage.

New to ducting? Read our guide: What is Ducting? Types, Sizes & Materials Explained.