A row of Clearvent roof mounted natural ventilators in-situ


The Clearvent a roof mounted louvre natural exhaust ventilator that can extract large volumes of warm, stale or contaminated air. Aerodynamically designed to maximise efficiency and throughput.


Ideally suited to areas requiring a large exhaust opening, such as factories or commercial areas where heat would otherwise cause unrestricted internal temperature rise.
In the open position these units provide almost clear daylight openings and consequent psychological relief to personnel working in an enclosed environment.

Energy Conservation

Interlocking blades are fitted with energy conserving draught strips to minimise heat loss when closed.


The ventilator construction has integral rain discharge channels.
The unit has an integral base skirt to fix down and flash to all types of building structures including roof upstands.


Manufactured using aluminium BS EN 485 alloy, louvre blades, drainage channels, control arms and actuators are secured to the main ventilator body.


Available in throat widths ranging between 460mm and 1676mm, and with throat lengths from 834mm up to 2836mm.

Aerodynamic Testing

The unit was subjected to a series of independently controlled tests to determine the aerodynamic performance of the design.
Aerodynamic co-efficient – 0.68


  • Internal closure trim flashings
  • Bird guards or insect mesh
  • Security guards
  • Extended base flanges


Manual Nylon covered wire cable to:

  1. Clam Cleat/Clutch Control – variable setting.
  2. Winch – variable setting.
  3. Friction loaded – variable setting.

Pneumatic For day to day opening and closing, also enables optional connection to temperature sensors/building management systems.

Electric Actuation For day to day opening and closing, also enables optional connection to temperature sensors/building management systems.


Louvre blades are pivoted on double bush nylon bearings. Maintenance should be carried out in accordance with McKenzie-Martin’s recommendations.

System Design & Product Selection

Assistance with scheme design and product selection is offered by our experienced technical team.



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