If using operable windows, locate as many people as possible close to them. The credit allows you to count a person as having access to an operable window if they are within a 20-foot depth and a 10-foot length from one. The operable portion of the window

If using operable windows, locate as many people as possible close to them. The credit allows you to count a person as having access to an operable window if they are within a 20-foot depth and a 10-foot length from one. The operable portion of the window must also be at least 4% of the size of the floor area of the space accessible to a given window, per ASHRAE 62.1-2004. For example, for a 5-foot-long window plus 10 feet on either side the total qualifying floor area would be 25 (5 + 10 + 10) multiplied by 20, or 500 ft2. At 4% of the floor area, the operable window area must be at least 20 ft2. Refer to the Documentation Toolkit for a diagrammatic representation of the window-area-to-floor-area relationship.