Onion Type Airflow Ridgevent

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Onion Type Airflow Ridge Vent

Onion-type Airflow Ridgevent is an economical, effective, and low-maintenance method of exhausting heat, moisture, and air-borne contaminants from industrial and commercial buildings. By taking advantage of natural thermodynamic forces, ridge ventilators offer a sustainable solution to improving energy efficiency, without moving parts. Airflow Ridgevent™ is ideally suited to the extraction of low to medium heat loads, with virtually no running costs or maintenance. Best for solar panel roofs in the future.


  • Natural ventilation – No running expenses
  • Efficient airflow – cooler building
  • Assemble unit – easy installation
  • Knockdown form – cost-effective, damage resisting
  • Extensive size range – suits most designs
  • No moving parts – low maintenance
  • Compound design – resists rainwater entry
  • Self-draining – no additional plumbing
  • Mesh guarding provides bird and vermin barrier
  • Suitable – solar panel installation building
  • Warranty 36 month
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Throat (T) (W) (H) (D) Purline Distance (A)
300 800 404 860 400
450 900 404 960 550
600 1100 516 1150 700
Note:- All Dimensions in MM
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Material: PPGI, PPGL, and Galvalume to match the colour combination of the existing roof

Onion-type airflow ridgevent ventilators are constructed from Galvanised, Galvalume, Colour coated Galvalume aluminium, stainless steel, powder-coated steel, and pre-painted material.

Abridged Air Change Table

Situation Air changes per hour *
Boiler Houses 20 - 30
Compressor Rooms 30 - 60
Engine Rooms 20 - 30
Factories (workshops) 6 - 10
Furnace Shops 30 - 60
Garages 8 - 12
Kitchens (Commercial) 15 - 20
Laboratories 4 - 6
Machine Shops 6 - 10
Paint Shops 30 - 60
Poultry Houses 6 - 10
Warehouses 4 - 8
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The air changes up to eight an hour provides for removing contamination normally caused by human occupants. The greater rates of air change allow getting rid of steam and heat in regions with moderate temperatures. If you live in hot regions, amount of air changes per hour must at a minimum be increased by two.

The most suitable RidgeVent depends on the number of air changes required per hour and the size of the building.

To calculate the suitable ridgevent size the usage of the building should first be determined and then the relevant number of air changes specified (see table 1). For instance, a structure that is used for boiler rooms will require around 25-40 air exchanges per hour compared with the 4-8 hours of air change required in warehouses.

It is then appropriate to calculate the ventilation rate:

To calculate the suitable ridgevent size the usage of the building should first be determined and then the relevant number of air changes specified (see table 1). For instance, a structure that is used as a boiler room would require around 25-40 air exchanges per hour, compared with 4-8 changes of air per hour in an industrial warehouse.


Q = L x W x H x A 3600
Q = required volume flow rate in m3 per second.
L = Length of building in meters.
W = Width of building in meters.
H = average height of building in meters.
[(Wall ht. + Ridge ht.)/2]
A = required air changes per hour.
3600 = Conversion constant.
For example, to ventilate a building 60 meters long,30 meters wide and 6 meters high with a required air change rate of 5 air changes per hour (for building to be used for Warehouse)-
Q= 60 x 30 x 6 x 8 3600
Q = 24 m3 per second
Assume effective stack height = 6m, then refer to (Table 2) for the exhaust velocity
Assume length of ridgevent as 55m, Assuming a wind velocity of 2m/s.
Temperature difference between Then use 1.32 m/s, for exhaust velocity Outside & inside of ridgevent of 6°C,
FORMULA=24/55 x 1.32 ventilator size = 330 mm, therefore use throat size 300 mm.

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Temp. Diff. Exhaust K (°C) Effective Stack Height (m) Wind Velocity m/s
0 1 2 3
Boiler Houses 3 0.31 0.66 1.01 1.37
6 0.43 0.79 1.14 1.50
9 0.53 0.88 1.24 1.59
12 0.61 0.96 1.32 1.67
15 0.68 1.04 1.39 1.75
6 3 0.43 0.79 1.14 1.50
6 0.61 0.96 1.32 1.67
9 0.75 1.10 1.46 1.81
12 0.86 1.22 1.57 1.93
15 0.97 1.32 1.68 2.03
9 3 0.53 0.88 1.24 1.59
6 0.75 1.10 1.46 1.81
9 0.91 1.27 1.62 1.98
12 1.06 1.41 1.77 2.12
15 1.18 1.54 1.89 2.25
12 3 0.61 0.96 1.32 1.67
6 0.86 1.22 1.57 1.93
9 1.06 1.41 1.77 2.12
12 1.22 1.57 1.93 2.28
15 1.36 1.72 2.07 2.43

The above velocities are indicative only and when used in the formula shown will determine the approximate Ridge vent throat size

Spacing / Support

Onion-type Airflow Ridgevent frames must be installed at the spacings given in dimension D of the table at left or less. Purlin must be positioned to allow attachment of the frame on the purlin flanges as defined by dimension E. Designers are reminded to allow for point loadings applied to the purlins for both dead and wind loadings.


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Harnessing Natural Thermodynamic Forces: The Benefits of ONION Airflow Ridgevent™ for Solar Panel Roofs Building
In the process of allowing people around the globe to adopt renewable energy options solar panels are now an extremely popular method of harnessing the energy that the sun has. However, the efficient operation of solar panels is heavily dependent on maintaining an optimal temperature and space available for the solar panels installation. To address this challenge, ONION Airflow Ridgevent™ offers a sustainable and effective solution by taking advantage of natural thermodynamic forces. we will explore why ONION Airflow Ridgevent™ is the best choice for solar panel roofs, offering efficient energy utilization and a range of additional benefits.

Natural Ventilation with Zero Running Expenses

One of the key advantages of ONION Airflow Ridgevent™ is its ability to provide natural ventilation without any running expenses. The ridge ventilators leverage the principle of convection to facilitate the movement of air, allowing hot air to escape from the roof space while drawing in cooler air from the louver opening. This passive cooling method ensures that the building remains cooler, reducing the overall cooling load and improving energy efficiency.

Efficient Air Flow for a Cooler Building

By efficiently channelling airflow, ONION Airflow Ridgevent™ helps in maintaining a cooler building interior. As hot air rises, it accumulates near the roof, and without proper ventilation, it can result in increased temperatures. The ridge ventilators create a pathway for the trapped hot air to escape, ensuring a consistent flow of cool air that helps in maintaining optimal operating temperatures. This not only maximizes their efficiency but also extends their lifespan of structure.

Pre-Assembled Unit for Easy Installation

Installing ONION Airflow Ridgevent™ is a hassle-free process due to its pre-assembled unit design. This feature allows for quick and straightforward installation, saving time and effort during the setup phase. The ease of installation also makes it a viable option for retrofitting on roofs, ensuring that the benefits of improved ventilation can be enjoyed without significant disruption or additional expenses.

Knockdown Form for Cost-Effectiveness and Damage Resistance

The knockdown form of ONION Airflow Ridgevent™ offers cost-effectiveness and excellent resistance against damage. Additionally, the ability to dismantle the unit ensures that any potential damage can be addressed by replacing specific components rather than the entire system, resulting in cost savings and reduced environmental impact.

Extensive Size Range to Suit Various Designs

ONION Airflow Ridgevent™ is available in an extensive size range of throat sizes of 300, 450, and 600mm, making it suitable for various roof designs and any roof profile sheets configurations. Whether you have a small residential or a large commercial or industrial project, there is a size option to fit your specific requirements. This versatility ensures that every solar panel roof can benefit from the improved ventilation and energy efficiency provided by the ridge ventilators.

No Moving Parts and Low Maintenance

With no moving parts, ONION Airflow Ridgevent™ offers low maintenance requirements. The absence of mechanical components reduces the risk of breakdowns and eliminates the need for regular servicing. Once installed, the ridge ventilators continue to provide efficient ventilation without the need for ongoing maintenance, saving both time and money.

Compound Design to Resist Rainwater Entry

The compound design of ONION Airflow Ridgevent™ is specifically engineered to resist rainwater entry. The ridge ventilators are designed to withstand heavy rain and prevent water leakage, ensuring that the building remains dry and protected. This feature is particularly crucial for solar panel roofs, as it helps maintain the integrity and performance of the panels.

Self-Draining Design with No Additional Plumbing

ONION Airflow Ridgevent™ is self-draining, eliminating the need for additional plumbing. The ridge ventilators are designed to efficiently handle rainwater runoff, preventing water accumulation on the roof and reducing the risk of leaks. This self-draining capability further enhances the reliability and long - term performance of roof system.

Mesh Guarding for Bird and Vermin Barrier

To protect entry in roof space, ONION Airflow Ridgevent™ incorporates mesh guarding, which serves as a barrier against birds and vermin. The mesh prevents unwanted entry, ensuring that the building remains free from damage caused by nesting or infestation. This added layer of protection enhances the overall durability and functionality of the industrial roof installation.

Suitable for Solar Panel Installation Buildings

ONION Airflow Ridgevent™ is specifically designed with solar panel installations in mind as they are installed at the apex of the roof where there most good ventilation for building and leaving total roof space for the installation of solar panels. Its unique features and benefits align perfectly with the requirements of solar energy systems, offering enhanced energy efficiency, temperature control, and long-term performance. By choosing ONION Airflow Ridgevent™, solar panel owners can optimize their investment and enjoy the full benefits of sustainable energy production. When it comes to solar panel roofs, ONION Airflow Ridgevent™ stands out as the best choice for harnessing natural thermodynamic forces. By providing natural ventilation, efficient air flow, and a range of additional benefits such as easy installation, low maintenance, and resistance against rainwater entry, this sustainable solution ensures optimal energy efficiency without the need for moving parts. With ONION Airflow Ridgevent™, solar panel owners can maximize the performance and longevity of their solar energy systems while contributing to a greener future.


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