Frequently asked Questions

What is Passive Ventilation?
Why do we need it?
How does it work?
Is it a proven solution?
Where can we use it?
What is a Cold Roof?
What is a Warm Roof?
Is passive ventilation better than mechanical ventilation?
Will the vents let birds and insects in?
What does it cost to install in a home?


What is Passive Ventilation?

Passive ventilation is a method of allowing continuous airflow into a building with the objective of eliminating condensation by removing the warm air from the roof void.

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Why do we need it?

Condensation is a huge problem in NZ mainly due to poor building design. NZ weather tightness requirements have been specified for several decades without the required ventilation which causes condensation. From this, mould is easily formed which is a major contributor to the alarmingly high level of asthma and respiratory diseases in NZ.

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How does it work?

In a balanced system, wind blowing over the ridge creates a negative pressure that draws the warm air out of the attic/roof space. Replacement air enters through the under eave or soffit vents, bathes the underside of the roof, and exits at the ridge cap through the ridge vent. Even with no wind, the natural convection action of rising warm air maintains a continuous airflow along the underside of the roof. It is a system that works year round with no moving parts or energy consumption.

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Is it a proven solution?

Yes the systems we provide have been tried and tested across Europe & USA covering the most extreme climatic conditions. Passive ventilation has been mandatory overseas for over two decades.

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Where can we use it?

There is a wide range of products covering every eventuality so they can be utilised in homes, offices, commercial buildings and are especially effective in classrooms. Tests have shown that freshly circulated air prevents students from tiring in the afternoons which produces improved performances.

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What is a Cold Roof?

A Cold Roof is a roof with a void or attic space which can be easily ventilated.

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What is a Warm Roof?

A Warm Roof is a roof with no attic space and is generally associated with a flat roof, inclined ceiling or a mono-pitch roof design. A specific system is utilised for this type of roof.

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Is passive ventilation better than mechanical ventilation?

Firstly passive ventilation is free air, costs nothing to run and requires no maintenance. Also if the mechanical ventilation has no external vent to fresh air, it will just be circulating the warm and moist air from the roof space into your home. If this is the case, mould can form inside the ducting and the spores will be circulated into your home. This can trigger asthma and respiratory diseases especially in elders and infants.

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Will the vents let birds and insects in?

The mesh and grille sizes have been tried and tested and the recommended gap is set at 4mm. This has been tested to prevent the ingress of nesting insects and obviously birds and vermin. Tests show that a vent of 3mm or less can retain water and paint etc and block the airflow. Water will run out of a 4mm grille.

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What does it cost to install in a home?

Passive ventilation products are mainly recycled plastic so they are extremely affordable and simple to install. Compared to mechanical ventilation, passive ventilation can cost up to 60% less with no ongoing maintenance costs.

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