3 key considerations 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.
2.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.
3. 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.
Download our whitepaper, How to specify the right weather louvres, if you want to know how to write a good specification for weather louvres.
Paul Compton is a Technical Director for Colt, experienced in smoke control, HVAC, solar shading and louvre systems.