Double Casement Window: A Complete Guide for Homeowners

When you want unobstructed views, excellent ventilation, and a clean modern look, a double casement window delivers on all three. Consisting of two side-hinged sashes that crank outward like doors, this configuration floods a room with light and air while sealing tightly against the elements when closed. Whether you are replacing tired old windows or planning new construction, understanding how double casements work, what they cost, and where they shine will help you make a confident choice.

What a Double Casement Window Is

A casement window is hinged on the side and swings outward, operated by a crank handle rather than sliding up or down. A double casement, sometimes called a French casement or a двойной unit, places two of these sashes side by side within one frame. Depending on the design, they may share a central post (mullion) or, in a true French casement, meet in the middle with no center post at all, opening to a completely clear span. Both sashes crank open, giving you a wide, unobstructed opening that captures breezes far better than a double-hung window of the same size.

Key Advantages

Double casement windows are popular for several practical reasons:

• Superior ventilation: Both sashes open fully, and the outward-swinging design can even scoop passing breezes into the room.
• Energy efficiency: When closed, the sash presses tightly against the frame, creating an excellent airtight seal, often better than sliding windows.
• Unobstructed views: Especially in French casement versions with no center post, glass fills nearly the entire opening.
• Easy operation: A simple crank opens the window with minimal effort, ideal over sinks or countertops where reaching is awkward.
• Security: Multi-point locking systems and hook-shaped locks embedded in the frame make casements hard to force open.

Materials and Frame Options

Double casement windows come in the same frame materials as other window styles, each with trade-offs. Vinyl is the most affordable and low-maintenance, resisting rot and never needing paint. Fiberglass is stronger and more stable, handling temperature swings without warping, at a higher price. Wood offers classic beauty and can be painted or stained but requires upkeep and costs more. Aluminum-clad wood combines a wood interior with a weatherproof exterior. Composite frames blend materials for durability and efficiency. Your choice affects price, appearance, insulation value, and how much maintenance the window will demand over the years.

What It Costs

Pricing varies with size, material, glass package, and installation. For a single double casement unit, expect roughly $400 to $1,200 for the window itself, with premium wood or fiberglass units and large sizes reaching higher. Installed, including labor and any trim or repair work, a typical double casement runs about $600 to $1,800 per window. French casement versions with no center mullion cost more due to their more complex hardware. Whole-home replacement projects benefit from volume pricing, but casements generally sit above basic single-hung windows and below large custom picture or specialty units in price.

Common Sizes

Double casement windows are available in a wide range of dimensions and are frequently custom-sized for replacement openings. As a general guide, individual casement sashes are often 1.5 to 3 feet wide, so a double unit commonly spans roughly 3 to 6 feet in total width, with heights from about 2 to 6 feet. Because they must swing outward, very wide sashes become heavy and can sag over time, which is one reason two narrower sashes are paired rather than a single huge one. Always measure your rough opening carefully or have an installer confirm before ordering.

Where They Work Best

Double casements excel in specific locations around the home. They are a favorite above kitchen sinks and counters, where the crank is easier to reach than a stubborn sliding sash. They suit bedrooms and living rooms wanting maximum airflow and light, and they meet egress requirements in many basements and bedrooms when properly sized, providing a code-compliant emergency exit. They also pair beautifully with scenic views, since the wide glass area maximizes what you see. Avoid placing outward-swinging casements over walkways, patios, or decks where an open sash could obstruct foot traffic.

Potential Drawbacks

No window is perfect. Because casements swing outward, they can interfere with exterior spaces and cannot accommodate window-mounted air conditioners. The crank mechanism and hinges are moving parts that can wear out or need adjustment over time, unlike the simpler hardware of a fixed or double-hung window. Screens mount on the interior, which some homeowners find less convenient. In extremely high-wind areas, an open casement can catch gusts, so they should be closed in storms. And large or premium units carry a higher price than basic window styles.

Double Casement vs. Double-Hung

Homeowners often compare these two. A double-hung window has two sashes that slide vertically and sits flush with the wall, making it better near patios and compatible with window AC units, plus both sashes tilt in for easy cleaning. A double casement ventilates better, seals tighter for improved efficiency, and offers a cleaner, more contemporary look with larger unobstructed glass. If airflow, views, and energy performance top your list, the casement wins; if you want traditional styling, AC compatibility, and no exterior swing, the double-hung may fit better.

Is It Right for Your Home?

A double casement window is an excellent choice for homeowners who value fresh air, abundant natural light, tight energy sealing, and a crank that is easy to operate in hard-to-reach spots. It suits kitchens, bedrooms, and rooms with views particularly well. Weigh the outward swing against your exterior spaces, budget a bit more than for basic windows, and choose a frame material that matches your maintenance appetite. Do that, and a double casement will brighten your rooms and cut your energy bills for decades to come.

Understanding Glass Packages and Efficiency Ratings

The glass in a double casement window matters as much as the frame for comfort and energy bills. Standard efficient windows use double-pane insulated glass with a Low-E (low-emissivity) coating that reflects heat, and an inert gas fill like argon between the panes to slow heat transfer. In extreme climates, triple-pane glass adds another layer of insulation and noise reduction. When comparing windows, look at the NFRC label: a lower U-factor means better insulation, while the solar heat gain coefficient (SHGC) tells you how much solar heat passes through, which you want low in hot southern climates and moderate in cold northern ones. Because casements seal so tightly, pairing them with a quality glass package produces some of the most energy-efficient operable windows you can buy.

Cleaning and Maintaining Casement Windows

Casements are relatively easy to keep up if you tend to their moving parts. Because both sashes swing outward, you can reach the exterior glass from inside simply by opening the window, a real advantage on upper floors compared to double-hung units. Wipe the glass with standard cleaner and a microfiber cloth, and clean the weatherstripping so it seals well. The crank operator and hinges benefit from occasional lubrication with a dry silicone spray to keep operation smooth and prevent squeaks. Inspect the seals annually and check that the multi-point lock engages fully. If a crank feels gritty or stiff, it may need cleaning or eventual replacement, an inexpensive part that restores easy operation without replacing the window.

Installation and When to Hire a Pro

Replacing a window is achievable for an experienced DIYer working on an insert (pocket) replacement into a sound existing frame, but full-frame replacement and new-construction installs involve flashing, house wrap, and precise leveling that reward professional experience. A poorly installed casement can bind, leak air or water, or fail to seal at the lock, undoing the style’s efficiency advantage. Pros ensure the unit is plumb, level, and square, properly insulated around the frame, and correctly flashed to keep water out. For a whole-home project or any opening where sizing, structure, or waterproofing is in question, hiring a qualified installer protects your investment and often preserves the manufacturer’s warranty, which can be voided by improper installation.

Measure carefully, pick the right material and glass package for your climate, and consider a French casement where you want a truly open view, and this versatile window style will earn its place in your home.