How do you select the right performance louvre system for your application and environment? Often, the chosen performance louvre ends up being a compromise between airflow efficiency and rain defence. Specifying the wrong louvre system could cause problems internally to plant and machinery or surfaces behind the louvre, either through rainwater penetration or from restricted airflow.
In this article, Construction Specialties - CS advises buyers to ask 5 questions before making their decision on the most suitable performance louvre system for their environment.
1. Do you know the required airflow through the louvre?
One of the most important factors to consider when selecting ‘weather louvres’ is the design air intake velocity or face velocity. The higher the face velocity, the more difficult it is to prevent water penetration. Weather louvres are tested to AS NZS 4740-2000 by subjecting them to a range of face velocities (0.0m/s to 3.5m/s) to determine their rain defence performance. Know the performance of the louvre at your air intake velocity before specifying a product.
2. How efficient is your louvre?
The airflow efficiency of a louvre is determined by how freely it allows air to pass through, with the overall ‘aerodynamic free area’ determined by the aerodynamic coefficient (Cd) and face area of the louvre panel. When the resistance to air moving through the louvre is high, there will be a corresponding increase in the difference in pressure between the outside and inside of the louvre, known as the pressure drop.
Lower pressure drops mean less fan power is required, optimising energy consumption. Increasing the size of the louvre at the design stage means that the required volume airflow rate can be achieved at a lower face velocity and reduced fan power.
3. What amount of water penetration is acceptable for your project?
Weather louvres or rain defence louvres not only allow free flow of air but also keep wind-driven rain out. Acceptable levels of water penetration will depend upon the application and how important it is for the area beyond the louvre to stay dry. Before selecting your louvre, take a look at the AS NZS 4740-2000 water penetration banding. This test is based on an external wind speed of 13m/s with 75mm/h rainfall projected onto the front of the louvre panel. Whilst these bands have quite a wide range, they will at least give an idea about the class of louvre needed. Local weather conditions and topography naturally vary from place to place, so it is important to take into account the expected site conditions and compare them with the louvre test conditions.
4. Where are you installing your louvres?
Before selecting the louvre system, finalise the location, position and exposure of the louvres in the building.
5. How do you know the louvre you have chosen is right for your project?
Compare the simulated test results with the expected site conditions. Check the full range of face velocities that the louvre is tested to so that it will achieve the desired performance in the actual application.
Please note that the AS NZS 4740-2000 tests are based on a 1m x 1m test sample only; therefore, you will need to consider how the collected water is drained in larger louvre panels to prevent re-entrainment.
Contact the global louvre experts Construction Specialties - CS for advice or technical support in selecting performance louvre systems.