A weather louvre must admit or discharge the required air while managing the site's weather exposure. Free area, pressure loss and rain resistance are separate selection factors. A large percentage of open area does not by itself establish good rain rejection.
Use the correct area and airflow direction
The overall face area is different from the available passage through the blades and frame. Obtain free-area information for the actual size, including mullions or other features. Compare the pressure loss at the required intake or exhaust duty rather than using a velocity based on the wrong area.
Bird screens, insect screens and equipment behind the louvre can change the installed resistance and maintenance requirements. Include those components in the selection; do not add them after the fan duty has already been fixed.
Read what the rain test actually represents
AMCA's explanation of louvre testing distinguishes the still-air water-penetration test from wind-driven-rain conditions. A result from one test should not be presented as universal waterproof performance.
Describe local exposure, building height and the consequences of water reaching the space behind the opening. A sheltered plant-room wall and an exposed façade can require different arrangements. The project designer should select the appropriate evidence and water-management detail.
Provide a place for water and maintenance
Coordinate drainage, flashings and the wall interface. Water retained in a blade or frame needs a planned route out; sealing the wrong opening during installation can defeat that route. A plenum or drainage provision behind the louvre may be part of the complete design.
Provide access to clean screens and remove debris. A blocked screen changes resistance, and maintenance from an inaccessible façade can be much more difficult than anticipated. Check the size and weight of removable sections before ordering.
For the weather-louvre arrangements in our aluminium air-opening range, shengtongJH can coordinate size, finish and installation interfaces. Send airflow, exposure and wall details to establish a suitable configuration and evidence requirement.