Free Area Calculator

A = Minimum distance between the head and top blade*.

Note: Where the top blade dimension C is less than A, use the value for C

Note: If you do not know A see the optional inputs for Header Height and Sill Height or Jamb Width (for vertical products)

B = Minimum distance between the sill and bottom blade*

C = Minimum distance between adjacent blades

Note: that in louver Type 2, C may not be equal to C1*. Type 2 Louver is when there is no B and the bottom blade touches the frame. So, enter C1 in B

Note: This is not the same measurement as Blade Spacing. This is the Opening inside of two blades.

N = Number of C openings in the louver

L = Minimum distance between louver jambs

Note: Essentially L = Width - (Jamb Width * 2)

* The A, B & C spaces shall be measured within one inch from each jamb and averaged

Note: When measuring two louvers placed back to back, the free area for the combined louvers shall be determined as the smaller of the two free areas.

If this is a vertical blade product (uncommon). See Type 4 for proper inputs.

For Horizontal products, if we do not know the A value, We can use the Header Height and Sill Height to determine it. A = Height - Header Height - Sill Height - B - (N * Blade Spacing).

For Vertical products, if we do not know the A value, We can use the Jamb Width to determine it. A = Width - (Jamb Width * 2) - B - (N * Blade Spacing).