Egress windows are required in every room used for sleeping purposes (bedrooms) on any floor and in basements with habitable space.

If you are constructing a new home, the code requires that you put an egress window in each bedroom. It also requires an egress window in the basement if habitable rooms will be finished in the basement. If you install a basement bedroom, an egress window is required in each bedroom but you need not provide another egress window if there are other habitable rooms in the basement. The bedroom window(s) suffices for the habitable rooms.

If you have an existing home and you add a sleeping room in an unfinished basement, the code requires that you install an egress window in the sleeping room or rooms. Likewise, if you create habitable space in your basement other than a bedroom and you currently do not have an egress window, the code requires that you install one as part of the installation of the habitable room.

An egress window must satisfy four International Residential Code (IRC) criteria:

• Minimum width of opening: 20 in
• Minimum height of opening: 24 in
  At first glance, you might assume that a 20" by 24" window would be acceptable for egress. However, those dimensions would yield a net clear opening of only 3.3 sq ft. To achieve the required net clear opening of 5.7 sq ft, a 20" wide window would have to be 42" high. Likewise, a 24" high window would have to be 34" wide.
• Minimum net clear opening: 5.7 sq ft (5 sq ft for ground floor)
  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, but the actual opening a person can crawl through. Nearly all window manufacturers specify which of their windows meet national egress requirements right in their catalogs and list the net free opening of their windows. The salesperson who sells you the window should be able to help you select a code-compliant window, provided he/she knows you need an egress window.
• Maximum sill height above floor: 44 in

The window opening must be operational from the inside without keys or tools. Bars, grilles and grates may be installed over windows but must be operational without tools or keys and still allow the minimum clear opening.

Increasing an existing window opening

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 might mean 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.

A wide variety of window designs can be used for egress windows. You should select a window design that meets your architectural, aesthetic, space, and financial limitations. (Dimensions shown are for illustrative purposes only.)

• Casement windows with hinged sashes that swing free and clear of the opening can be relatively small and still meet egress requirements. This makes them ideal for basement egress and for other areas where space is limited.
• Some manufacturers can install a special operator arm that allows the window to open wider than the standard 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.

• Glider or slider windows have sashes that fill nearly half the possible window opening. They require a window nearly twice the size of a casement window.
• 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 window must be nearly 4' 9" in overall height. This height requirement makes it undesirable for most basement egress situations.

• Awning windows are problematic. Since the opened sash prevents escape from most window wells, they're unsuitable for basement egress. And with most awning windows, the center opening hardware and height don't meet egress requirements. Some manufacturers offer models with special detachable operators that meet egress requirements.

Window wells must:

• allow the rescue window to open fully.
• provide 9 square feet of "floor area," with a minimum dimension of 36 inches in width and in length.
• contain a permanently affixed ladder or steps for climbing out if the window well depth exceeds 44 inches in depth. The ladder must be at least 12 inches wide and project no less than 3 inches from the window well. It cannot be obstructed by the open window or encroach on the required window well dimensions by more than 6 inches.
• if located under a deck or porch, the top of the window well must be more than 4 feet from the bottom of the deck or porch joists
• have a guardrail around the egress well if an egress window well is adjacent to a walkway or stoop and is more than 30” deep.

Window wells may be made of rust-resistant metal, treated wood, wood naturally resistant to decay, concrete, masonry, or plastic. Some window well designs have steps built or molded into them. Covers are permitted.