Casement or Single Hung? What Replacement Windows Do to Bedroom Egress

Audie Builds — October 10, 2026

When you replace windows, the new ones are not always the same style as the old ones. Tall casements are the usual case: many window lines stop making casements around 72 inches tall, so a taller opening gets a single hung or double hung in its place. Some lines are not made as casements at all.

The frame size stays the same, so from the street nothing looks wrong. What changes is how big a hole you can climb through once the window is open, and for a bedroom that is a code question. This guide shows how much the opening changes, the four numbers code checks, and how we make sure every bedroom still has a legal escape window before a single custom window is ordered.

At a glance

• Bedroom escape window: Opens at least 5.7 sq ft, 20 in wide, 24 in tall, sill no higher than 44 in
• Ground-floor window: 5.0 sq ft is enough when the sill is close to the ground outside
• 35½ × 59½ casement: Opens about 10.5 sq ft
• Same size single hung: Opens about 5.9 sq ft
• Double hung: Opens no bigger than a single hung for escape
• When we check: At the permit review, before anything is ordered

Why a casement turns into a hung window

A casement is hinged on one side and swings out with a crank. A single hung has two halves stacked on top of each other, and the bottom half slides up. A double hung lets both halves slide.

Casements have a height limit, because a tall sash swinging on its hinges puts a lot of weight on the hardware. Many lines stop around 72 inches, and a few go taller. When a home has casements taller than the line you choose can build, the manufacturer quotes a single or double hung for those openings. We ask manufacturers for exactly that, so every opening gets a window the line actually builds at that size.

Some lines are not built as casements at any size, and sometimes a manufacturer quotes a hung window where a casement would have worked. Either way, your proposal lists every opening that changes style, what it changes to, and why.

Same frame, very different opening

The drawing at the top of this page is to scale. Both windows are 35½ by 59½ inches. The casement swings almost completely out of the way, so nearly the whole frame is open: about 10.5 square feet. The single hung can only open its bottom half, so you get about 5.9 square feet. Same wall, same frame, a little more than half the opening.

A double hung does not fix that. You can lower the top half instead of raising the bottom one, but only one half is open at a time, so the escape opening is the same as a single hung.

Those numbers are our estimates from published opening sizes. Manufacturers publish the exact clear opening for their windows, and that is the number that decides it at inspection.

The four numbers code checks for a bedroom window

The residential building code (IRC section R310) says every sleeping room needs at least one window you can escape through, and that window has to meet four numbers:

5.7 square feet of clear opening (5.0 for a ground-floor window whose sill is close to the ground outside). 20 inches of clear width. 24 inches of clear height. And the sill can be no more than 44 inches above the floor.

Width and height alone are not enough: 20 by 24 is only 3.3 square feet, so a short, wide hung window can pass both and still fail on area. That is exactly what happens when a mid-size casement becomes a single hung.

Only one window per bedroom has to meet this. Living rooms, kitchens, bathrooms, stairwells and garages do not. Cities around Dallas-Fort Worth enforce different editions of the code, but these four numbers are the same in all of them.

Why a replacement loses its pass

Code gives replacement windows a break. A new window does not have to meet the four numbers if it is the largest standard size that fits the existing opening and it is either the same style as the old window or a style that opens as big or bigger.

A casement replaced with a casement keeps that pass. A casement replaced with a single hung opens smaller, so it loses it. If that window is a bedroom's escape window, it now has to meet all four numbers on its own. Upstairs, a 35½ by 59½ single hung at about 5.9 square feet is just over the line, and a thicker frame can push it under.

Want to keep your casements? Add a transom on top

If you love the look of casements, or a bedroom needs the bigger opening, a tall opening does not have to become a hung window. We can order a casement short enough for the manufacturer to build and join a fixed transom window to the top of it. The two units are joined at the factory or on site into one assembly that fills the same opening in your wall.

In a 35½ by 83½ inch opening, a single tall single hung opens about 8.6 square feet. A 59½ inch casement with a 24 inch transom above it opens about 10.5 square feet, because the casement still swings fully out of the way. The sill stays where it was, so the escape opening starts at the same height.

A few things to know. It costs more than one hung window, because it is two windows joined together. The transom does not open. And a joining bar runs across the window where the two units meet. For many homes, especially bedrooms and rooms where the casement look matters, it is the best of both.

Window codes in the cities we serve

The four escape-window numbers are the same in every city below. What changes from city to city is the energy limit for the new windows and whether replacing them needs a permit.

Cities on the 2024 code allow a U-factor of 0.30 or lower. Cities still on the 2021 code adopted the regional amendment that allows 0.32, and The Colony kept that number when it moved to 2024. Garland still enforces the 2015 code at 0.35. The solar heat gain limit is 0.25 everywhere. A window rated U 0.30 and SHGC 0.25 or better meets the code in every city we serve, and that is the rating we look for first.

No permit does not mean no rules. Dallas only skips the permit for a window of the same size and type, so a casement becoming a single hung is not covered. Allen only skips it when the new window does not shrink an emergency escape opening. Either way, the escape-window check still applies.

Checked October 10, 2026 against each city's adopted-code ordinance and building department pages. Codes and permit rules change, so we confirm with the city on every job.

How we handle it before anything is ordered

Replacement windows are made to order and cannot be returned, so the check has to happen first. This is our process on every window job:

At the walkthrough we mark which rooms are bedrooms and which window in each one is the escape window. In the proposal you see every opening that changes style, the reason, and how big it opens before and after, with the close calls flagged. At the permit review, before we order, we pull the city permit and check each bedroom's escape window against the manufacturer's published opening.

If one comes up short, we change it with you in writing before ordering. The usual fixes: a shorter casement with a fixed transom joined on top, a casement from a line that builds it at that height, a different style for that one window, or a size change where the wall allows. Installation starts after the permit is issued.

If you are comparing window quotes, ask each company which of your casements they are changing to hung windows, and whether they checked your bedroom openings. If you want us to look at yours, the form below reaches us directly, or see our general contracting services.

Frequently asked questions

Is a double hung better than a single hung for egress?

No. A double hung lets both halves slide, but only one half is open at a time, so its escape opening is about the same as a single hung of the same size.

Does every window in my house have to meet egress?

No. Each bedroom needs one window that meets the four numbers: 5.7 square feet open (5.0 at ground level), 20 inches wide, 24 inches tall, and a sill no higher than 44 inches. Other rooms do not have this requirement.

My old casement passed. Will the new window automatically pass too?

Only if it is the same style, or a style that opens as big or bigger, and the largest standard size that fits. A single hung in place of a casement opens smaller, so it has to meet the four numbers on its own.

Why can't I just get tall casements?

Some manufacturers build them and many stop around 72 inches tall. When the line you choose cannot build a casement that tall, it quotes a hung window instead. If keeping casements matters, we can join a shorter casement to a fixed transom on top so it fills the same opening, or price a line that builds casements that tall.

What energy rating do replacement windows need in my city?

Around Dallas-Fort Worth the limit is a U-factor of 0.30, 0.32 or 0.35 depending on the code your city enforces, and a solar heat gain coefficient of 0.25. A window rated U 0.30 and SHGC 0.25 or better passes in every city we serve. The table above lists each city.

How do you make sure the right windows get tempered glass?

Code requires tempered safety glass in or next to doors, in tub and shower areas, near stairs and landings, and in large panes low to the floor. We mark those at the measure and list them on your proposal, and the city inspector checks them at the permit review, so you get a second set of eyes before anything is ordered.

Do you pull a permit for window replacement?

Yes, where the city requires one, and we apply before ordering so the escape-window check happens while there is still time to change a window.