AS/NZS 4740-2000 sets out the guidelines for the testing and classification of all weather or performance louvres. During testing, the resistance to airflow is assessed and the louvres are subjected to 75mm/hr of water, blown against a 1m x 1m louvre at a velocity of 13m/s. The louvre is then given a 3 part classification:
- Discharge Loss Coefficient (DLC)
- Wind Loading
Part 1: Louvre Effectiveness (or Penetration Class)
This classification rated A-D designates the “Effectiveness” Class of the weather louvre against water (rain) penetration. Each class covers a specific range and it can be seen from the table below that a Class A is significantly more effective than the Class B below it:
|Class||Effectiveness||Max. allowable penetration of rain litres/hr|
|A||1 to 0.99||0.75|
|B||0.989 to 0.95||3.75|
|C||0.949 to 0.80||15|
|D||Below 0.8||Greater than 15|
Louvre performance is dependent on the intake velocity. i.e. a Louvre may be class A with an intake velocity of 0m/s but at 3.5m/s it might be a D.
Part 2: Airflow Class
This classification, rated 1-4 designates the louvres ability to allow air to pass through it and is determined by establishing the Discharge Loss Coefficient (DLC) at various airflow velocities. Each class covers a specific range, as can be seen in the table below. The higher the DLC the less resistant to air the louvre is, with a DLC of 1 being ideal, although no louvre product will ever be able to achieve that. In simple terms, a hole in the wall with no louvre would have a DLC of 0.7 or above depending on the size of the hole. The Airflow Class gives a guide to M&E consultants of how the louvre performs at various ventilation rates and the actual DLC figure is used to establish the actual area of louvre required.
|Airflow Class||Discharge Loss Coefficient (DLC)||Rating|
|1||0.7 & Above||Excellent|
|2||0.5 to 0.699||Very Good|
|3||0.3 to 0.499||Good|
|4||0.1 to 0.299||Fair|
Part 3: Wind Loading
To test a louvre’s ability to withstand wind loading the louvre is mounted in a frame or on a panel and a uniformly distributed load is applied using positive pressure or a static load to simulate the action of wind forces. The louvre’s wind load performance level is then graded based on the loading it has been able to withstand, see table below:
|Performance Level||Test Load (m/s)||Test Load (km/hr)|
At the end of the testing the louvres are examined to ensure that their structural integrity has not been compromised by the applied loadings.
Generally assessors are looking to make sure there has been no loosening of seals and fasteners, distortion of members, structural damage or functional damage.
For more information on the standard and AS/NZs 4740-2000 compliant louvre models, please get in touch:
- Phone: 1300 272 602
- Email: email@example.com
To buy a copy of the standard please visit SAI Global