Pre-Insulated Duct — PIR Panel Ductwork

Pre-insulated duct is ductwork made from rigid PIR panel faced with aluminium on both sides, cut and folded into sections on site so the insulation and the duct are one component. It needs less void height and is much lighter than GI ductwork, but it is less robust, pressure-limited, and its PIR core is combustible.

By Dhruv Agarwal · · 1 min read

What it is

Ductwork made from rigid PIR panel faced with aluminium on both sides, cut and folded into sections on site. The insulation and the duct are the same component.

Specification at a glance

PropertyTypical specification
PanelPIR core, aluminium facings both sides
Panel thickness20mm — 30mm typical
FacingAluminium foil, thickness stated
StandardEN 13403 for non-metallic ducts
Fire classNamed EN 13501-1 classification
Pressure limitStated by manufacturer; not unlimited

Against GI ductwork

Pre-insulated PIRGI with wrap
Void height neededLessMore
WeightMuch lighterHeavy
Install sequenceOne operationFabricate, fit, then insulate
RobustnessLower; damages easilyHigh
Pressure capabilityLimitedWide range
Outdoor useNeeds weather jacketStandard

Where it earns its place

Tight ceiling voids in fit-outs where the slab-to-slab height is fixed and services must be stacked · refurbishments where structural hanger capacity is limited · fast-track programmes where removing the separate insulation trade saves real days · low and medium pressure comfort cooling in office space.

Where projects go wrong

  • Used in the wrong location — kitchen extract, exposed plant rooms, or outdoors without a jacket.
  • Fire class not checked against the route the duct takes.
  • Joints poorly made. The system relies on correct corner profiles and taping; a rushed joint leaks and the aluminium facing tears.
  • Hangers over-tightened, crushing the panel and reducing the free area.
  • Pressure class exceeded, causing panel deflection and joint failure.

Standards referenced

Non-metallic duct requirements under EN 13403. Reaction-to-fire classification to EN 13501-1. Duct insulation requirements under ECBC 2017.

Standards referenced

  • EN 13403 — Ventilation for buildings — non-metallic ducts (CEN-CENELEC)
  • EN 13501-1 — Reaction to fire classification (CEN-CENELEC)
  • ECBC 2017 — HVAC — duct insulation (Bureau of Energy Efficiency)

Frequently asked

Height, weight and time. The insulation is the duct wall rather than a wrap applied afterwards, so the overall section is smaller for the same free area — which matters when the ceiling void is tight and services are stacked. It is a fraction of the weight of GI, so hanger loads drop, and it is one trade and one operation instead of fabricate, install, then insulate.

It depends on the product and where it runs. The panels are aluminium faced with a PIR core, so the core is combustible even though the facings are not. Products have a named EN 13501-1 classification and that class must be checked against the application, particularly in escape routes, shafts and high-occupancy spaces. It is not a substitute for a fire-rated duct where one is required.

Outdoors without a designed weather jacket, in kitchen extract carrying grease, in high-pressure systems beyond the manufacturer's stated limit, and anywhere the duct is exposed to impact. The panel is far less robust than GI, so plant rooms, car parks and service corridors where ladders and trolleys pass are better served by sheet metal.

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