Short answer: Colorado follows the International Residential Code, which requires every basement, habitable attic, and sleeping room to have an emergency escape and rescue opening, with some exceptions. When the opening is a window, it must provide a minimum net clear opening of 5.7 square feet, a minimum width of 20 inches, a minimum height of 24 inches, and a sill no higher than 44 inches above the floor. The opening must work from inside without special knowledge, and a side-hinged or sliding door can serve the same purpose.
This guide covers when an egress window is needed, the details behind those numbers, plus window well sizing, drainage, and what to look for if you are upgrading an existing window.
What Is an Egress Window?
An egress window is specifically engineered to let people escape during an emergency situation. This includes any window installed in a bedroom or sleeping room, a habitable attic, or a finished basement. Residential codes state that every bedroom must have two means of exit, and the egress window serves as the secondary means of escape when the bedroom door is not an option.
Most Colorado municipalities have adopted the International Residential Code (IRC) for basement egress, though local amendments are common. Always contact your local building inspector before installing a new system to avoid added expense down the road. Windows above grade are not regulated as strictly statewide, and are not covered in this article, but an egress ladder should be available for any bedroom above the ground floor or below ground level.
Where Egress Openings Are Required in Colorado Homes
Under IRC Section R310, an emergency escape and rescue opening is required in any of these spaces:
- Every basement
- Every habitable attic
- Every sleeping room, on any floor
- Each individual sleeping room inside a basement
Renovations follow the same rule: any new sleeping room or basement needs its own opening. Exceptions include basements under 200 sq ft used only for mechanical equipment, and basements with an automatic sprinkler system installed under Section P2904 that also have two means of egress.
Under Section R310.3, the opening can be a window or a side-hinged or sliding door, but a door only works when the room opens directly to a yard. For most basements, attics, and interior bedrooms, a code-compliant window is the practical choice.
Colorado Egress Window Sizing and Code Authority
Colorado egress window sizing follows the International Residential Code, which local jurisdictions adopt and enforce with their own amendments. The Division of Fire Prevention and Control enforces the 2021 editions of the IBC, IRC, IFC, IMC, IEBC, and IECC for public schools, junior colleges, and some health facilities (plus the 2024 IFC), and the Colorado State Plumbing Board has adopted the 2021 IPC, IFGC, and plumbing chapters of the 2021 IRC. Homes in wildland-urban interface areas also fall under the Colorado Wildfire Resiliency Code, adopted statewide in 2026. Check with your local building inspector since regulations published online may be incomplete or out of date.
IRC Clear Opening Dimensions (Section R310)
An egress window must provide a minimum net clear opening of 5.7 square feet, a minimum width of 20 inches, a minimum height of 24 inches, and a sill no higher than 44 inches above the finished floor. Dimensions are measured with the window in the fully open position. For a crank-out casement window, the area between behind the open sash and the side of the window well often does not count in the measurements, so the rough opening typically needs to be larger. Smoke detectors in or near every sleeping room are a separate but related code requirement.
Helpful tip: A bench or step stool placed under the window helps children and less mobile family members reach the sill during an emergency exit.
How Egress Windows Must Open
How the window opens is just as important as how large it is. It has to open from inside without keys, tools, removable handles, or multi-step releases. A child or guest unfamiliar with the house should be able to reach the latch, flip it, and push the sash open in one motion. Anything that requires removing security bars, storm windows, or screens first fails the requirement, since a complicated lock wastes precious time when seconds count.
Below-Grade Window Wells and Drainage
When the sill of your egress window sits below the adjacent ground elevation, a window well gives the rescue opening the clearance it needs. Under IRC, the well must meet these requirements:
- 9 square feet minimum horizontal area
- 36-inch minimum projection (width and length)
- Permanently affixed ladder if depth exceeds 44 inches
- Approved alternative, such as a bulkhead enclosure
Ladder rungs must be at least 12 inches wide and spaced no more than 18 inches apart, and the ladder cannot extend more than 6 inches into the well’s opening. For a crank-out window, plan placement carefully since the area behind the open sash often gets subtracted from the opening.
Drainage
The well should also extend 8 to 10 inches below the sill so rainwater or snowmelt can drain into the soil or reach your foundation drain. Under the United Soil Classification System, well-drained soil, such as a sand-gravel mixture, lets water move freely, while heavier clay soils call for a drainage system tied into existing drain tile. Fill the bottom of the well with 6 to 10 inches of clean river rock or pea gravel.
Common Types of Egress Windows
Several window styles can meet Colorado egress requirements. The right choice depends on your wall space, window well dimensions, and budget.
Inswing casement windows hinge on one side and swing into the room. The full sash clears the frame, so the clear opening is nearly the full size of the window. Inswings work well in snowy Colorado climates because the sash is not blocked by snow or ice in the well.
Crank-out casement windows swing outward into the well. They offer strong ventilation and a tight compression seal. Plan the well size carefully, since the open sash takes up part of the well’s clear opening when in the fully open position.
Slider windows move horizontally along a track. Only one side opens, so the overall frame needs to be roughly twice the size of a casement window to meet the same 5.7 square foot minimum net opening.
Whichever style fits your project, every Window Well Experts egress window is built with welded vinyl frames, insulated Low-E glass, and screens that remove from the inside. Each window ships fully braced for poured wall installation and can also serve as a replacement window in an existing opening.
Window Well Covers
A window well cover keeps debris, pests, rain, and snow out of the well while preserving direct access for emergency exit. To stay code-compliant, every cover must open easily from inside the well with no special knowledge or tools, support a reasonable snow load, and not interfere with the window’s fully open position.
Please keep in mind that crank-out windows often need an Atrium or Super Slant cover if the window is above the rim of the well. Low profile covers will prevent the window from opening, preventing the egress from being code compliant.
Material and size both matter. Polycarbonate covers let natural light reach the basement and work well for standard climates, while steel grate covers handle the heavier snow loads common in Colorado’s mountain regions. Whatever the material, the cover should match the well’s footprint so it sits flush without gaps. Escape hatches are available for covers over 60” x 38” if needed. Hinges are also available to make the cover easier to open.
Why Egress Windows Matter
Egress windows save lives. They give everyone in the home an emergency escape option, and they give first responders a way in. A finished basement also needs a code-compliant egress window to count as legal living space, which matters for permits, insurance, and resale.
Long-Term Benefits of Installing an Egress Window
Beyond safety, the long-term payoff is real. A finished, code-compliant bedroom can add thousands to resale value, and the natural light and fresh air make basements livable instead of just usable. If you are unsure whether your existing window meets current Colorado standards, have it inspected or upgraded. Get multiple estimates and verify each contractor’s credentials before signing.
Get Help Choosing the Right Egress Setup
Window Well Experts ships egress windows, window wells, covers, and permanently affixed ladders anywhere in the United States. If you are finishing a basement in Boulder, replacing an old window in Pueblo, or planning new construction along the Front Range, our team can help you match the right products to your local code requirements and operational constraints.
Call 1-888-397-7936 or submit a contact form to talk through your project with an expert. For more reading, see our guide on egress ladders and our comprehensive egress window well buying guide.