How do I find an air leak in my window?

Author: Juliet Treutel  |  Last update: Thursday, April 30, 2026

Light an incense stick and carefully pass it around the edges of common leak sites. Wherever the smoke wavers or is sucked out of or blown into the room, there's a draft. You can also use a damp hand to locate leaks; any drafts will feel cool to your hand.

How to find where a window is leaking air?

You can take a candle, lighter, or burning stick of incense to find if there's an air leak. Simply run the lit candle slowly around the window and watch the flame, see if it dances one direction or the other...that's an air leak.

How to detect a leak in a window?

On a cold day, hold your hands an inch away from the window frame and feel for any drafts. If you can't see or feel air leaks, then conduct a flame test with a candle. Light the candle and trace the outline of your window. If the flame and smoke pull in one direction, then you have found an air leak.

What tool can I use to see air leaks in my house?

Using a blower door along with a thermal imaging camera is one of the best ways to find air leaks in a building envelope. The blower door acts as an amplifier for the camera.

How to detect drafty windows?

It will be easy to detect any draft from your windows. For a more dramatic test, you can use smoke from a lit incense stick. Pass the stick close to the edges of your windows, looking for any noticeable change in the way the smoke rises. If there is a draft, the smoke should waiver and get blown inwards.

How to check for air leaks in your windows | Long Island Home Inspector

How to figure out where draft is coming from?

Start by checking your attic, basement and crawl spaces for any cracks, gaps and openings where cold air may be coming through. You can also try a smoke test. On a windy day, shut all windows and doors, and turn off all appliances. Then hold a lit incense stick next to potential air leakage spots.

How do you stop cold air leaks in windows?

7 Ways to Keep Cold Air from Coming Through Windows and Doors
  1. Use weather strips.
  2. Install new door sweeps.
  3. Apply foam tape.
  4. Insulate with window film.
  5. Hang insulated curtains.
  6. Recaulk windows and doors.
  7. Use a door snake.

How to find gaps in windows?

Check Window Frames and Seals: Examine window frames, sashes, and seals for any visible gaps or cracks. Use an incense stick or smoke pencil around the edges to detect drafts—if the smoke wavers, you may have air leaks. Common sources of air leakage in windows are worn-out seals and loose frames.

Where are the biggest air leaks usually found in homes?

Most people call these air leaks "drafts." You may feel these drafts around windows and doors and think these leaks are your major source of wasted energy. In most homes, however, the most significant air leaks are hidden in the attic and basement.

What is the app for finding air leaks?

The SDT LEAKChecker is an ultrasound leak detection solution designed to find compressed air and vacuum leaks in noisy environments. LEAKChecker measures the level of ultrasonic signal in decibels. Convert the measurement to flow rates with the SDT LEAKReporter, a free App for iOS and Android.

How do I find the source of a window leak?

Here are some common areas to check:
  1. Checking the sealed area between the window frame and the glass. ...
  2. Examine the window sill on the exterior of the house. ...
  3. Clean around your window frame to clear out dirt and debris that's built up over time, including around weep holes and the window sash.

Where do windows leak the most?

Where Does Window Rot Most Likely Occur? Rot leaks occur through or around the frame of the window. The frame is the fixed part of the window that is attached to the structure of the home. Rot leaks through the frame typically occur at the lower outside corner joints of the exterior window sill.

How to fix drafty windows?

5 Quick and Easy Fixes for Drafty Windows
  1. Weather stripping. Weather stripping can stop cold air from entering your home, especially if there are visible cracks or gaps in your windows. ...
  2. Window caulking. ...
  3. Window film. ...
  4. Shades and curtains. ...
  5. Draft blockers.

How to test for air leaks in windows?

Perform a Light or Candle Test

If light is coming through the window frames, you can be sure cold air is leaking through the windows as well. The candle test is even a better way to detect air leaks in windows. Simply light a candle and trace the edges of the window frames with the lit candle.

Why is my window unit leaking inside my house?

A clogged condensate drain line is one of the most common causes of air conditioner water leakage. Over time, this line can become clogged with algae, dirt, dust, and debris. When this happens, the line backs up and overflows from the drain pan, causing the water to leak into your home.

How do you diagnose a leaking window?

You may see black fuzz, mildew growth, or mold building up in an area on the window frame inside or outside your home. You may also see moisture between the panes of glass, cracking and bubbling paint, or warping of the window components.

What is the best method to find air leaks?

Light an incense stick and carefully pass it around the edges of common leak sites. Wherever the smoke wavers or is sucked out of or blown into the room, there's a draft. You can also use a damp hand to locate leaks; any drafts will feel cool to your hand.

How to test window insulation?

The Flashlight Test

Wait until the sun sets. Then, go outside while a second person shines a flashlight around the edges of the window from inside the house. If you can see pinpricks of light shining through the frame, you have a problem. After all, if light can pass through, so can air.

What tool is used to detect air leaks in homes?

Use an air leak detector

There are two main types: thermal leak detectors and ultrasonic leak detectors. Thermal leak detectors work by detecting temperature differences in the air. Ultrasonic leak detectors work by detecting sound waves that are produced by air leaks.

What is an air leak test?

What is Air Leak Testing? Air leak testing is an effective method of determining if a product has been manufactured to meet leak-tight specifications. Microscopic holes, failed seals, and countless other defects can cause air leaks that can lead to significant problems.

Why is there a gap around my window?

Gaps around windows, for instance, are primarily managed to accommodate the natural expansion and contraction of materials when temperature changes occur.

How to check window and door seals?

First, inspect the weatherstripping on the door or window by looking for any missing chunks and or damage. You can also see if there is any light shining through the seal by closing the window/door. These are signs that you should replace the stripping.

How do you seal an air leak around a window?

In areas where gaps are less than ¼ inch, use caulk to seal the area. If the area is greater than ¼ inch of a gap, use sealing foam. If there is a seal where a window opens or closes, replace the seal.

Why is cold air coming through my bedroom windows?

Cold air comes through windows if there's an issue with the window frame, the locking mechanisms, the hardware, the weatherstripping, or the caulking. Gaps can form between the window frame and the wall if the windows aren't installed properly or as a result of a shifting foundation.

Where to caulk around windows?

Apply caulk to all joints in the window frame, and do not forget the joint where the frame and wall meet. Hold the gun or product at a 45-degree angle, and caulk in one continuous stream. Make sure the caulk sticks to both sides of a crack.

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