Think you need a Whirlybird for roof ventilation? Introducing E-Vent®, the next generation in roof ventilation.

Roof ventilation is an excellent way of removing hot air from your roof space, and assisting in the energy efficiency of your home.

A hot roof space in summer will mean that your air-conditioner will have to work harder to achieve a comfortable temperature within your home. With rising energy costs, it’s important to implement simple, yet effective heat reducing measures in your home.

The CMI Ridge Vent, E-Vent® is a highly effective system which extracts hot air from the roof space. E-Vent® harnesses the combined natural forces of differential air pressure and convection.


E-Vent® is the new generation in roof ventilators. It sits at the highest part of your roof, along the ridge line, barely noticeable from the ground level making it an attractive option for your home. And the best part, E-VENT® is easy to install. Simply remove a section of your ridgecap, and replace with your E-VENT. No need for cutting holes or difficult installations.


Unlike the traditional Whirlybird ventilators, E-Vent® has no moving parts and will never need repair or replacement. Furthermore E-Vent® sits at the highest point of the roof allowing hot air to be extracted efficiently and effectively.


  • E-Vent® reduces heat indoors
  • E-Vent® is a part of the roofline and is barely noticeable
  • E-Vent® provides protection from airborne embers
  • E-Vent® effectively removes noxious gases, airborne bacteria and household odours
  • E-Vent® reduces air conditioning costs
  • E-Vent® is a low, one off cost
  • E-Vent® requires absolutely no maintenance
  • E-Vent® is a no cost, no fuss installation

How does E-Vent® work?

Using principles first expounded by Bernoulli and Venturi in the 18th century, Architect Ean McDonald created his E-Vent® natural ventilating system, now available in various forms from Combined Metal Industries. Bernoulli propounded that the pressure of a moving body of air or water is least where the velocity of the mass is greatest. In simple terms, by accelerating an air flow across a given surface or opening, a pressure differential can be created to produce a natural force and that harnessed force can produce power.

It is applied in aircraft flight and venturi systems generally. E-Vent®’s harness this natural power by creating low pressure areas on the upper and downwind sides of the vents creating a natural and effective exhausting air pump. That in turn means that air at normal pressure within a building will be literally sucked out by wind flow. And on the stillest of air days, E-Vents® still work by reason of simple convection or ‘stack effect’.


Other applications

  • Ridge vent strips
  • Sloped roof skylights
  • Flat roof skylights
  • Vents for wet areas such as bathrooms, kitchens or toilets
  • Condensation prevention and extraction
  • Fire warning vents
  • High fume or dust extraction
Note: CMI also stocks a range of the traditional Whirlybird style products. Contact our sales team today for more information about E-Vent® and roof ventilation.
E-Vent® is manufactured by Combined Metal Industries to ISO 9002 standards E-Vent® Patent No. 673749.