How to Plan Egress Windows in Your House
Step 1
What Are the Requirements for Egress Windows?
According to the International Building Code, “Basements and sleeping rooms below the fourth story shall have at least one exterior emergency escape and rescue opening. . . . Such opening shall open directly into a public street, alley, yard or court.”
This “escape and rescue opening” can be a bedroom window, skylight or patio door, but it must meet certain criteria:
- It must have a minimum net clear opening of 5.7 sq. ft. Net clear opening refers to the actual free and clear space that exists when the window is open. It is not the rough opening size or the glass panel size or any other size, but the actual opening a person can crawl through. Code officials want the opening large enough so firefighters can comfortably crawl through the window in full protective gear with an air tank on their back. Ground-floor bedroom windows only need a net clear opening of 5 sq. ft.; they can be smaller because a rescue ladder doesn’t take up part of the opening.
- The opening height must be at least 24 in., and the opening width must be at least 20 in.
- The bottom of the clear opening must be within 44 in. of the floor.
- The window or other opening must be operational from the inside without keys or tools. Bars, grilles and grates over windows must be operational without tools or keys and still allow the minimum clear opening.
Note that a window opening that’s the bare minimum of 24 in. high and 20 in. wide does not meet egress requirements, since its net clear opening is only 3.33 sq. ft. A window has to be taller and/or wider than these minimums to meet the 5.7-sq.-ft.-opening requirement.
All these numbers may seem daunting, but selecting a new one or installing an egress window doesn’t need to be. Window manufacturers list the net free opening of their windows and skylights in their catalogs, and whether they meet egress requirements.
Step 2
How to Choose Egress Window Size
When it comes to egress, not all bedroom windows are created equal. There are several styles of windows used in home construction, and they can all be made to meet egress requirements—some just do it more space efficiently than others. As you remodel, you’ll want new egress windows that match the style of the existing windows and meet egress requirements. This can be a challenge. Bear in mind these pros and cons.
Casement windows: These side-hinged windows fulfill egress requirements while taking up the smallest amount of wall space. This makes them ideal for egress windows in basements or other areas where space is limited. Some manufacturers can install a special operator arm that allows the window to open wider than the standard bedroom window size operating arm to meet egress requirements. Others have an operator arm that can be pushed to open the window wider in an emergency. These meet egress requirements as long as you leave the “PUSH HERE” label in place.
Double-hung windows: Even when it’s fully open, more than half of a double-hung window’s overall area is blocked by glass. This means that to meet egress window height requirements, a bedroom window must be nearly 4 ft. 9 in. in overall height. This height requirement takes it out of the running for most basement egress situations. Plus: Here’s how to fix a double hung window.
Gliding windows: To meet egress requirements, these horizontally sliding windows must be at least 4 ft. wide and 4 ft. high. This extra glass area and the light it lets in are pretty darn nice in a basement area, if you have the space.
Awning windows: These top-hinged windows make lousy egress windows. They don’t meet egress requirements in basements because the opened sash impedes entrance and exit. And those with center opening mechanisms don’t meet code because the hardware gets in the way. Only those with special hardware will meet egress requirements—and there aren’t many available.
Certain skylights meet egress requirements as long as they’re installed within 44 in. of the floor.
If you’re replacing a smaller window with a larger one that meets egress requirements, bear in mind that enlarging the height of the opening takes less structural work than enlarging the width. Increasing width means installing a larger, beefier horizontal structural header over the window opening—a major project. Increasing height is often only a matter of lowering the height of the sill below the window.
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