Quick answer
How is rooftop plant and external ductwork insulated against the weather?
External plant and ductwork are insulated with a weatherproof core — mineral wool or phenolic — sealed in aluminium cladding or PIB membrane that sheds rain and blocks UV. The cladding is detailed with laps, drips and sealed penetrations so water cannot get behind it, and the whole assembly is fixed for wind loading with safe access for installation.
Why does external insulation need a weatherproof finish?
Mineral wool and phenolic hold water if rain reaches them, which destroys the thermal value and corrodes the pipe. A continuous weatherproof skin — aluminium cladding or PIB — keeps the core dry so the insulation performs for the life of the plant.
Aluminium cladding or PIB — which is used?
Aluminium cladding is rigid and durable, used on pipework and flat duct faces where a hard finish is wanted. PIB is a flexible membrane, used on irregular shapes and where a lighter finish is acceptable. Both shed water when detailed with correct laps and seals.
How is UV and rain exposure handled?
The cladding or membrane is UV-stable, and all laps face away from the prevailing weather. Drips are formed so water runs off, not along, the surface. Penetrations — supports, instruments — are sealed with compatible mastic so water cannot track in behind the cladding.
How is the assembly fixed for wind?
External insulation is secured with banding or fixings rated for wind loading, and the core is pinned to the substrate. On large ducts, the cladding is braced so it does not drum or lift in high winds, which would otherwise fatigue the fixings.
How is access managed for the work?
Rooftop work uses planned access — MEWPs, scaffold or edge protection — agreed before the team mobilises. External insulation is installed in phases that suit the access and the weather, so the core is never left exposed overnight without protection.
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