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Louver-Free Area
A high-percentage free area is great because it allows for more air to enter via a smaller opening, thus reducing the expenses involved in opening up the wall and installing louvers. The free areas usually range from 35% to 60% of a wall opening.
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Water Penetration
The ‘Point of Water Penetration’ is where the louver system allows the water to pass through it. It is a measurement of free area velocity that tells us the threshold at which the louver will start leaking.
For traditional louver designs, this varies from 300 fpm (feet per minute) to 1250 fpm, with the latter denoting an excellent resistance to water entrainment.
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Resistance to Airflow (Pressure Loss)
Every louver will create wind resistance based on its design as well as the shape of its frame and blades, and anything that obstructs the airstream creates resistance – such as ductwork, filters, coils, the building structure itself.
The louver’s resistance is measured by running air through it and then calculating the pressure differential and free area velocities. It is essential to minimize this resistance where possible because it can be harmful to the louver and other air movement equipment. It is also vital to ensure lower energy consumption, as the lower the pressure, the less power will be required to operate the fan.
