Roof Ventilation

Achieving calculated, continuous and unimpeded airflow through the roof cavity is relatively straight forward. Whilst it is possible to retrofit passive ventilation solutions to existing buildings, it is highly recommended to incorporate passive ventilation during the design phase of any new building project.

Recommended airflows of either 10,000mm² per linear metre (equivalent to 1/300) or 25,000mm² per linear metre (equivalent to 1/150) are determined by the pitch or the design of the roof and can be easily achieved using recommended product combinations.

As building codes continue to evolve, the basic principles remain the same. Recommended airflow can be easily achieved at the eaves of the roof. However, roofs with lower pitches or cathedral/skillion designs require a larger ventilation open area (25,000mm² per linear meter) compared to higher pitched roofs (10,000mm² per linear meter). It is crucial to use products in combination, following the recommended technical details, to ensure the essential elements of calculated, continuous, and unimpeded passive ventilation are achieved.
Please note that airflow recommendations are specifically applicable to traditional or cold roof designs. For warm roof or passive house designs, product placements and airflow rates may vary.
When considering passive ventilation, it is important to take into account other relevant Australian Standards, such as AS 3959, which applies to buildings located in bushfire-prone zones.
Disclaimer: The information and recommendations provided herein are based on our expertise and understanding. However, it is advisable to consult with professionals and adhere to local regulations and guidelines for specific building projects.

Calculated, continuous, unimpeded passive ventilation is a critical ingredient in the essential ventilation of a building. Using tried and tested international proven best practice, VENT Systems Airflow calculations are determined by the pitch and type of roof and exceed minimum National Construction Code Vol 2, Part 10.8.3 requirements

Traditional Roof Pitch <10°

  • A calculated airflow of 25,000mm² per linear metre (or 1/150) at opposing end
  • Product combination – FV25 Over Fascia Vent , RR650 Roll Panel Vent (insulation guard) and DBFR Ventilation & Drainage Batten
Traditional Roof Pitch >15° <75°

  • A minimum calculated airflow of 10,000mm² per linear metre (or 1/300) at the eaves and 8,000mm² per linear metre per side at the high level (Apex)
  • Product combination – FV10 Over Fascia Vent , RR650 Roll Panel Vent (insulation guard), RV10 (P or DT) Ridge Vent and DBFR Ventilation & Drainage Batten 10mm

Traditional Roof Pitch >10° <15°

  • A calculated airflow of 25,000mm² per linear metre (or 1/150) at the eaves and a minimum of 8,000mm² per linear metre per side at the high level (Apex)
  • Product combination – FV25 Over Fascia Vent , RR650 Roll Panel Vent (insulation guard), RV10 (P or DT) Ridge Vent and DBFR Ventilation & Drainage Batten

Cathedral Roof PitchAny Degree Pitch

  • A calculated airflow of 25,000mm² per linear metre (or 1/150) at the eaves and a minimum of 8,000mm² per linear metre per side at the high level (Apex)
  • Product combination – FV25 Over Fascia Vent , VB20 Ventilation & Drainage Batten 20mm, RV10 (P or DT) Ridge Vent and DBFR Ventilation & Drainage Batten 10mm
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When applying in BAL Rated areas, external vents can be covered in BAL Rated mesh up to a rating of BAL-40. Compliance with AS3959 must be adhered to.