If you have ever written a louvre specification, you will know how large a number of variables you have to deal with in order to select the right louvre for your design.
Here are some resources and key considerations to help you when specifying weather louvres.
Let’s get the negatives out of the way first. Percentage free area is not a key consideration. It tells you nothing about the performance of the louvre, but it seems to be ingrained in specifications nonetheless.
The key considerations fall into three areas: aerodynamic performance (pressure loss through the louvre), resistance to rain entry, and exposure and wind loads.
The pressure loss will depend upon the design of the louvre (aerodynamic coefficient, not percentage free area) and the inlet or exhaust air velocity. Most louvres perform slightly differently depending upon the direction of the air flow.
Resistance to rain entry
The quantity and throw of water entering a building through a louvre system will depend upon the design of the louvre, the exposure to wind and rain, and the inlet air velocity. Not all louvres on a project will necessarily need the same performance, which is why our Colt Universal Louvres offer 3 levels of performance with no change of external appearance.
If you have a tall louvre bank the drainage arrangements for water from the louvre become important, not something that is shown up in tests on a standard 1m2 panel.
Exposure and wind loads
Exposure to wind also affects mullion spacing and support requirements. High wind loads mean closer mullion centres and/or more support, reducing the area available for air flow.
A good specification will:
- Provide an air flow rate and direction and a maximum pressure loss
- Set a rain rejection performance or class (HEVAC test method or EN 13030)
- Provide a structural design wind load.
Provide this and you’ll be sure to get the louvre you want.
Whitepaper - 'How to specify the right weather louvres'
Download our white paper if you want to know how to write a good specification for weather louvres.
Louvre selection program
Over the years we have helped many customers with their selection of the correct louvre system. We’ve created a tool to assist with this, based on what level of weather protection and aerodynamic performance is really needed. If you know the area of louvre or the airflow, the program provides the pressure drop. If you know the flow rate and the maximum pressure drop, it tells you the minimum size of louvre. It’s a simple tool that can considerably reduce the complexity of selecting the louvre that will give you the performance you need for your design.
Start using the Colt UL louvre selection program.
Paul Compton is Technical Director for Colt, experienced in smoke control, HVAC, solar shading and louvre systems.