Basement Bedroom Window: Escape Opening, Well Depth, Light and Ventilation
A 14-foot by 12-foot basement room (168 square feet, 8-foot ceiling) is being finished as a bedroom. Its only opening is a double-hung window at the top of a 52-inch-deep exterior well. The frame is 36 inches wide by 60 inches high, and the sill sits 48 inches above the finished floor. The lower sash provides 32 inches of clear width and 24 inches of clear height when fully raised. The well measures 46 inches wide by 60 inches long and has no ladder. This window provides the room's only glazing. The contractor argues that the room is fine because the window is large, opens, and the well has more than the required square footage.
1. Does this window qualify as an emergency escape and rescue opening? Work through each criterion, show the numbers, and list the corrections required.
Read the worked answer
Test each criterion separately, because the contractor is confusing total window size with clear opening.
- Net clear opening: 32 inches x 24 inches = 768 square inches = 5.33 square feet, which is less than the 5.7 square feet required. Fails.
- Minimum clear width: 32 inches, versus 20 inches required. Passes.
- Minimum clear height: 24 inches, versus 24 inches required. Passes, exactly at the limit.
- Sill height: 48 inches above the floor, versus 44 inches maximum. Fails.
- Well area: 46 x 60 = 2,760 square inches = 19.2 square feet, versus 9 square feet minimum, with both dimensions over 36 inches. Passes.
- Well depth: 52 inches, which exceeds 44 inches, so a permanent ladder is required. None is provided. Fails.
The opening must also be operable from the inside without keys, tools or special knowledge. Corrections: install a unit with at least 5.7 square feet of clear opening and a sill no higher than 44 inches, or enlarge and reconfigure the well so a compliant unit can be installed, and add a permanently attached ladder in the well.
2. Does the same window satisfy the light and natural ventilation requirements for a habitable room? Show the calculation and state the acceptable alternatives.
Read the worked answer
Use the floor area, not the window size, as the basis.
- Glazing: 8 percent of 168 square feet = 13.44 square feet required. The window provides 3 x 5 = 15 square feet of glazing, so this element passes.
- Natural ventilation: 4 percent of 168 square feet = 6.72 square feet of openable area required. The operable sash clears only 5.33 square feet, so this element fails by about 1.4 square feet.
The key judgment is that escape and ventilation are separate tests with different thresholds, so a window can pass one and fail the other. The 5.33 square feet used here is the same clear opening measured for egress, but it is compared against 6.72 rather than 5.7.
Acceptable paths: enlarge the operable sash to at least 6.72 square feet, or provide mechanical ventilation designed under the mechanical code. Separately, the glazing requirement can be met with artificial light averaging 6 footcandles at 30 inches above the floor, but that exception does nothing for the escape opening, which has no substitute.