Egress Window (Emergency Escape Opening) Check

IRC R310.2.1 sets THREE minimums that cannot all be met at once. Twenty inches of net clear width by 24 in of net clear height is 480 sq in -- 340.8 sq in SHORT of the 5.7 sq ft (820.8 sq in) the same section requires -- so one dimension always has to exceed its minimum, and this reports by how much: at 24 in tall the width must reach 34.2 in, at 20 in wide the height must reach 41.04. Meeting 20 and 24 and stopping there is the most common way an egress window fails inspection. Also checks the 44 in maximum sill height and the 5.0 sq ft grade-floor allowance. NET CLEAR opening only -- not the rough opening, the unit size, or the glass; a single-hung loses roughly half its height to the fixed sash. Window wells, openability, and releasable bars are separate.

net clear area = width x height; required = 5.7 sq ft (820.8 sq in), or 5.0 sq ft (720 sq in) for a grade-floor opening, or an override; width needed = max(20, required area / height); height needed = max(24, required area / width); pass requires width >= 20 in, height >= 24 in, area >= required, and sill <= 44 in.

IRC R310.2.1 (minimum opening area, net clear height, and net clear width, with the grade-floor exception) and R310.2.2 (bottom of the clear opening not more than 44 in above the floor), with all dimensions achieved through the normal operation of the opening from the inside.

The four dimensional criteria are short prescriptive sentences quoted in state adoptions, building-department handouts, and window manufacturers' free code guides. No table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: clear_width_in, clear_height_in, sill_height_in, location, clear_area_sqin, required_area_sqin, area_deficit_sqin, width_needed_in, height_needed_in, minimums_area_sqin, minimums_shortfall_sqin

• Minimum area 5.7 sq ft, or 5.0 sq ft for a grade-floor opening; overridableIRC R310.2.1
• Minimum dimensions 24 in net clear height and 20 in net clear widthIRC R310.2.1
• Sill height bottom of the clear opening not more than 44 in above the floorIRC R310.2.2
• The three minimums conflict 20 x 24 = 480 sq in, 340.8 short of 820.8; a partner dimension is always requiredarithmetic on the code values
• Net clear opening the free hole with the sash normally operated; not rough opening, unit size, or glassIRC R310.2.1 wording
• Not checked openability, window wells and ladders, releasable bars and grilles, which rooms need an openingstated scope limit