Drafty Windows: How to Check & Fix Windows With Seal Failure

Feeling cold even when you’re resting at home? Leaky windows could be to blame. These sneaky cold air leaks can make your place uncomfortable and increase your energy bills as an unpleasant bonus. But what causes drafty windows? Age, wear and tear, and poor installation can all lead to gaps and misalignments.

If you’re wondering how to seal drafty windows or how to find drafts in your home, this guide walks you through practical ways to diagnose the issue and stop a drafty window before it becomes a larger problem.

How to Test for Drafty Windows

Visual inspection

Drafty apartment windows can sometimes be so obvious that detection doesn’t even require special tools. Pay attention to corners and where the edges meet the frame. If you notice gaps or deteriorated weatherstripping, these are early indicators of air leaks.

You can also darken the room during the day and check whether any light escapes around the frame. If light passes through, air can too. For persistent leakage, exploring energy efficient windows can help you understand longer-term solutions.

Piece of paper test

Close the window on a standard sheet of printer paper and apply gentle tension to pull it free. A properly sealed sash should grip firmly. If the paper slides out with little resistance, the weatherstripping is worn or the frame alignment has loosened. 

Repeat the test along multiple points of the frame to identify whether the issue is localized or consistent across the entire sash.

Candle test

Hold a small lit candle several inches from the perimeter of the window and slowly trace the outline of the frame. Keep your hand steady and watch the flame’s behavior rather than the smoke. Noticeable flickering, leaning, or sputtering indicates air being pushed or pulled through gaps in the frame, typically around deteriorated seals, warped components, or loose latches.

Light-curtain test

Suspend a lightweight curtain, sheer panel, or even a thin scarf near the window. Observe how it behaves during breezy conditions or when your HVAC system cycles on. Any inward or outward movement suggests air is entering or leaving through unintended openings. 

This test is especially useful for older frames where subtle drafts are harder to detect visually.

Infrared thermometer

Scan along edges, corners, and the glass perimeter using a handheld infrared thermometer. Compare these readings to the surrounding wall temperature. Areas that register significantly colder (or warmer during summer) point to thermal transfer caused by leaks. 

This provides a more quantifiable method of detecting problem zones and helps distinguish between minor temperature variation and true air infiltration.

How to Fix Drafty Windows

Foam tape

Foam tape is one of the quickest ways to seal a drafty window, especially when you’re dealing with thin, inconsistent gaps around the frame. It presses into place easily, conforms to uneven surfaces, and immediately reduces airflow. Just keep in mind that foam naturally compresses over time, so the seal weakens with repeated opening and closing. 

It’s a solid short-term fix, but not a substitute for repairing failing hardware or replacing aging units.

Plastic window film

Plastic film kits create a temporary insulating barrier by covering the entire window opening with a thin, heat-shrunk sheet. When applied correctly, the film traps a layer of still air between the wrap and the window, which acts as insulation during colder months. 

It’s inexpensive, effective for winter drafts, and removable without damaging the frame. The tradeoff is that it blocks access to operable windows and must be replaced each season.

Removable caulk

Removable caulk is designed to seal gaps without committing you to a permanent material. It’s pressed into cracks around the sash or frame and peeled off later in one piece, making it ideal for rentals or cases where you only need insulation during specific months. While easy to apply, it’s best for narrow gaps; larger structural openings or deteriorated frames will overwhelm it quickly.

Clear nail polish

For hairline cracks in the glass itself, clear nail polish can create a temporary seal that prevents air and moisture from leaking through. It dries quickly and is nearly invisible once applied. 

That said, it only works for very small fissures and should be viewed strictly as a stopgap; any larger crack requires a professional repair or window replacement.

Thermal curtains

Thermal curtains use multiple fabric layers and insulating backing to reduce heat loss around drafty windows. They help retain warm air in winter and can noticeably reduce drafts in rooms with older windows. The main limitation is reduced natural light, since thicker fabrics must stay closed to offer meaningful insulation. They’re best as a supplemental tool rather than the primary fix.

Interior storm windows

Interior storm windows add a secondary pane inside your existing window frame, creating a sealed air pocket that improves insulation and reduces drafts dramatically. They’re more effective and longer-lasting than film kits, yet don’t alter your home’s exterior or require permanent remodeling. They cost more upfront but offer meaningful energy savings and comfort improvements if your frames are still structurally sound.

If the draft originates from the window style itself, these guides may help:

• Double-hung windows can become draft-prone as their upper and lower sashes age.
• Casement windows may leak when the compression seal wears out.
• Slider windows commonly develop gaps along the horizontal track.
• Picture windows are fixed and inherently more resistant to drafts.

What to Do When Nothing Helps

If DIY fixes don’t work or drafts repeatedly return, replacement may be the most reliable solution. Investing in modern replacement windows eliminates persistent sealing issues and improves energy efficiency.

When comparing materials, vinyl windows offer insulating frames and strong weather resistance, which helps reduce drafts long-term.

These additional resources can help you choose the best long-term solution:

• Energy-efficient windows: how much can I save?
• Comparing triple-, double-, and single-pane windows
• What are the basic window ratings you should know?
• Windows 101: a comprehensive guide to window types and styles

Final Thoughts

Drafts can sneak in through worn weatherstripping, misaligned sashes, or damaged frames. Temporary fixes help, but recurring air leaks usually indicate that hardware, seals, or glass components have aged beyond practical repair. Modern insulated windows provide tighter seals, better ventilation control, and lower energy costs.

If you’re ready for a long-term fix, Renuity can help you select energy-efficient, well-sealed windows tailored to your home’s needs. Contact us today to start on a solution to your window draft issues.