Egress Window (Emergency Escape Opening) Check
The bedroom-window check with a trap built into the code itself.
Example
You enter
- Net clear width (in) 20
- Net clear height (in) 24
- Sill height above the floor (in) 40
- Opening location above-grade
You get
- Clear area (sq in) 480
- Required area (sq in) 820.8
- Area deficit (sq in) 340.8
- Width needed at this height 34.20 in
- Height needed at this width 41.04 in
- Minimums area (sq in) 480
- Minimums shortfall (sq in) 340.8
Checked against published worked examples from: International Code Council.
Details, formula, and sources
ScopeIRC R319.2.1 and R319.2.2 [R310.2.1 in IRC 2021] set THREE minimums that cannot all be met by building to the dimensional minimums. 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.
Formula or tablenet 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 or below-grade 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.
Source and editionIRC R319.2.1 (minimum opening area, with the grade-floor exception) and R319.2.2 (net clear height and width) [both R310.2.1 in IRC 2021] and R319.2.3 [R310.2.3 in IRC 2021] (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.
Free accessThe four dimensional criteria are short prescriptive sentences quoted in state adoptions, building-department handouts, and window manufacturers' free code guides. No table is reproduced.
What governsEstimate. AHJ and licensed professional govern.
API field namesclear_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 or below-grade opening; overridableIRC R319.2.1 [R310.2.1 in IRC 2021]
- Minimum dimensions 24 in net clear height and 20 in net clear widthIRC R319.2.2 [R310.2.1 in IRC 2021]
- Sill height bottom of the clear opening not more than 44 in above the floorIRC R319.2.3 [R310.2.3 in IRC 2021]
- 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 R319.2.1 [R310.2.1 in IRC 2021] wording
- Not checked openability, window wells and ladders, releasable bars and grilles, which rooms need an openingstated scope limit