Double-hung windows remain one of the most common window styles thanks to their familiar design and flexible operation. They are versatile and easy to operate when everything is working as it should. But because they rely on multiple moving parts, double-hung windows are also more prone to air leaks and winter comfort issues.

Cold drafts, rattling sashes, and uneven temperatures near windows often trace back to a handful of predictable areas.

How Double-Hung Windows Are Built

A double-hung window has two operable sashes, an upper and a lower, that slide vertically within the frame. Each sash is supported by a balance system that counteracts its weight and keeps it in position.

Because both sashes move independently, the window relies on precise alignment, intact balances, and continuous weatherstripping to seal properly. When any of those components wear down or shift, air and moisture find a path through.

Where Winter Leaks Usually Begin

Most winter leaks in double-hung windows do not come from cracked glass. They come from gaps created by movement, wear, or age. Common leak points include:

• The meeting rail where the upper and lower sashes lock together
• The sides of the sashes where weatherstripping has compressed or torn
• The sill area where the lower sash meets the frame
• Balance channels that allow air movement inside the frame

These areas often look fine at a glance, but small openings become noticeable when cold air presses against the exterior of the window.

Sashes That Are Out of Square

Over time, sashes can shift slightly out of square. This can happen due to house settling, regular opening and closing of the window, or balance failure. A sash that is no longer square will not sit evenly against the frame. Signs of this issue include:

• A window that is harder to open or close on one side
• Uneven gaps between the sash and frame
• Locks that no longer align cleanly

Weatherstripping cannot make full contact when a sash is out of square, allowing cold air to slip through even if the window appears closed.

Correcting an out-of-square sash usually requires professional adjustment or repair. When properly squared, even pressure is restored along the seals, which significantly reduces drafts.

Balance Systems and Why They Matter

The balance system is what holds a sash in place when you open it. Older double-hung windows may use cord-and-weight balances, while newer ones often use spring or block-and-tackle systems. Several things can happen when balances wear out or break:

• Sashes may not stay open
• Windows may slam shut
• Sashes may tilt or sag slightly

That sagging creates gaps at the top or bottom of the sash, which are prime locations for winter air leaks. Restringing or replacing worn balances helps restore proper alignment and sealing.

Weatherstripping Does the Heavy Lifting

Weatherstripping is the unsung hero of double-hung window performance. It fills the small space between the sash and frame, blocking air movement while still allowing the window to operate.

Over time, weatherstripping can:

• Compress and lose resilience
• Crack or tear
• Pull away from corners
• Become brittle in cold weather

Failed weatherstripping often signals broader wear in the sash and balance system, which is why it’s a common issue on older windows. It’s often one of several signs that it may be time for window replacement.

Typical Gaps to Seal

Beyond the moving parts, there are a few static areas where leaks commonly start. Homeowners can check for:

• Gaps where the window frame meets interior trim
• Small openings at the sill corners
• Air movement behind side channels

These gaps often develop gradually and are easy to miss. Sealing them prevents cold air from bypassing the window assembly. In some cases, minor trim gaps can be sealed with caulk, but leaks tied to the frame, sill, or side channels may require professional evaluation or window replacement.

A Practical Maintenance Checklist

Before winter, homeowners can look for a few common signs that indicate a double-hung window is no longer sealing as it should. These checks don’t require tools or disassembly, but they can help determine whether a window needs professional attention.

Key things to look for:

• Sashes that sit unevenly or feel harder to operate on one side, which may indicate alignment or balance issues
• Windows that won’t stay open or close fully, often a sign of worn or failing balance systems
• Visible wear or flattening along weatherstripping, especially at meeting rails
• Air movement around interior trim or at sill corners, suggesting bypass leaks around the frame
• Locks that no longer pull the sashes together tightly, reducing seal compression

Some minor trim gaps may be sealed by a homeowner, but many of these conditions point to underlying wear in the sash, balances, or frame. Having a window replacement company evaluate the window is often the most effective next step.

Get in Touch With Window Zone About Double-Hung Window Replacement in Dallas, TX

Window Zone helps homeowners identify where double-hung windows lose performance and whether maintenance or replacement is the best next step. Contact us at 469.557.6333 to discuss your options.