A cool feeling beside a window is not always outdoor air entering through a gap. Identify whether air movement is concentrated at a joint, occurs across cold glass, or accompanies a window that does not close squarely. This prevents replacing a whole window or adding sealant before the source is understood.
Distinguish leakage from air cooling beside glass
Andersen’s air-infiltration guidance distinguishes outdoor leakage from window convection, where indoor air cools beside the glass and descends. Its product-specific checks include normal closure, weatherstrip condition and appropriate adjustments. The distinction is useful beyond that product, but adjustment instructions must match your own window.
Record where the movement is felt from indoors, whether it increases in windy weather, and whether the window is fully closed using its normal controls. A draft concentrated along a movable edge or frame joint deserves a seal/fit inspection; discomfort across the glass may also involve the glass temperature. These observations guide assessment and do not quantify leakage.
Do not use a candle, flame, smoke product, or a household depressurization experiment to find the leak. Do not climb outside or lean through an opening. If the sash is unstable, glass is damaged, or a high-level area must be accessed, stop and use an appropriate window professional.
Two air movements that can feel like the same draft
Fit, weatherstrip or the installation air seal may be relevant. Locate the joint before selecting a repair.
Cold glass can cool adjacent indoor air. Adding sealant cannot by itself change that glass temperature.
The repair question is whether outdoor air crosses a joint, indoor air moves beside a cold surface, or both occur. A strip added to the wrong place may leave the discomfort unchanged and interfere with normal closure. Andersen distinguishes infiltration from window convection.
Describe the exact edge or glass area and whether the sensation changes with wind. These observations help frame an assessment; touch and a diagram cannot certify airtightness. Preserve drainage openings and required ventilation, and use the opening/closing checks below before selecting weatherstrip or a stationary-joint sealant.
If the window does not close normally
Check for an ordinary visible obstruction in an accessible track with the window safely supported, and clean only as the owner manual permits. Use the normal latch without force. A sash that is crooked, binds, or needs heavy pressure to lock may require adjustment or hardware service.
Do not pull the window into alignment using the lock or add thicker strip to hide a fit problem. If it does not support its own weight, see the window-support guide. Fit should be corrected before judging the sealing performance.
If the moving edge has a damaged seal
Look for an accessible weatherstrip that is missing, loose, cracked or permanently flattened. Note the model and the affected edge before buying a replacement. Different profiles, compressions and installation methods serve different products. A generic strip that prevents normal closure can make the problem worse.
Natural Resources Canada’s window guidance identifies weatherstripping as a method for movable window components and notes the need to consider ventilation. Follow the window manufacturer’s replacement method and preserve its opening, closing and safety functions. Do not seal the sash permanently shut.
If air comes around the frame and wall
Record a visible gap, loose trim, deteriorated joint or a symptom beginning after installation. The route behind the trim can differ from the visible surface gap. An installer should assess the window-to-wall air seal and any related water-management detail where the source is concealed or unclear.
Natural Resources Canada’s material guidance distinguishes stationary joints from moving components. A compatible sealant may suit an identified stationary air-leak joint, but it is not a general instruction to caulk every opening around a window. Do not obstruct drainage/weep holes, vents, moving joints or required ventilation.
Avoid removing trim, applying expanding foam, or covering deteriorated material without the appropriate installation instructions. Water stains, softness or recurring moisture require source assessment before a cosmetic seal. If water is also present, use the condensation guide to distinguish surface moisture from other water entry.
Compare the result in similar conditions
After permitted maintenance or a professional correction, confirm normal opening, closure and locking first. Then compare the same area under reasonably similar wind and indoor conditions. A calm day immediately after sealing is weak evidence that a wind-related leak is fixed.
Give the professional the model, exact location, weather pattern, fit symptoms, recent work and any water damage. Ask whether the problem was sash fit, weatherstrip, the installation joint, or discomfort at the glass. If replacement is proposed, ask why repair is unsuitable; age alone or a cool sensation does not establish that the whole unit must be replaced.
