Louvres are windows with slats that offer only partial access to the outside. When evaluating a louvre you plan to install, the main sizing consideration is its free area. This defines how much of the louvre consists of empty space rather than the frame or the blades. Measuring free space manually is a difficult process. Calculating it is difficult as well because different models of louvre feature different proportions of free area. Online calculation tools, however, automatically calculate free area from the louvre's overall dimensions.
Navigate your browser to the free area calculator from the link in Resources.
Select your model from the page's drop-down boxes.
Enter the louvre's height and width in the corresponding text boxes. Select the "inches" check box if your measurements use inches, or select the "millimeters" check box if they use millimetres.
Click the page's "Calculate Free Area" button.