Not Every “Draft” Is Air Leakage

FGIA explains that perceived drafts can involve air infiltration, convection and radiant heat transfer. These mechanisms feel similar but require different responses.

• Air leakage: Outdoor air passes through or around the window under a pressure difference.
• Convection: Indoor air cools against cold glass, becomes denser and falls toward the floor.
• Radiant heat transfer: A person near a cold surface can feel cooler even without moving outdoor air.

A curtain moving, smoke deflecting at a seam or a pressure test showing airflow is stronger evidence of leakage than the statement “it feels cold.” Cold glass still affects comfort, but adding caulk will not change the center-of-glass temperature.

Five Places a Window Draft Can Begin

Product Leakage and Installation Leakage Are Different Claims

A product’s laboratory air-leakage rating describes the tested window specimen at specified conditions. It does not rate the field joint between the window and building. Conversely, a poorly sealed rough opening does not prove the manufactured window failed.

The investigation should isolate the path:

• Air through an operable joint may point toward lock, alignment, weatherstrip or product service.
• Air behind casing usually points toward the perimeter air-seal or adjacent wall.
• Air at exterior trim may travel from another wall location before emerging indoors.
• Whole-room pressure from exhaust fans or HVAC imbalance can intensify a small opening.

Contractors comparing window configurations can review Suburban Wholesale & Supply’s window products and Gentek window options.

A Step-by-Step Diagnostic Sequence

1. Document conditions: Record indoor and outdoor temperatures, wind direction, wind speed if available, HVAC operation and exhaust-fan use.
2. Locate the sensation: Determine whether it occurs at glass, sash, lock rail, frame corner, casing or wall.
3. Operate and lock: Confirm sash are fully closed, locks engage and the frame is not bowed or out of square.
4. Inspect weatherstripping: Look for folds, gaps, damage, paint, debris or missing pieces without modifying components.
5. Perform a paper check: ENERGY STAR suggests closing a window on paper; easy movement can indicate a loose contact area.
6. Use controlled air tracing: A trained professional can use a smoke pencil or similar tool safely while the building is under known pressure.
7. Inspect behind trim: If evidence points to the perimeter, carefully expose the cavity and evaluate insulation and air-seal continuity.
8. Escalate testing: Use blower-door diagnostics, infrared imaging under suitable temperature difference or a qualified fenestration evaluation when basic checks are inconclusive.

Testing Tools Can Mislead When Conditions Are Uncontrolled

Smoke moves in response to pressure, HVAC supply air and body movement. Infrared cameras show surface-temperature patterns, not air itself. A cold line may indicate leakage, missing insulation, thermal bridging or simply geometry.

A blower door can amplify leakage and help locate paths, but the operator must distinguish the window unit from the installation joint and surrounding wall. Testing before and after a repair is more persuasive than a single image without baseline conditions.

Avoid candles and improvised flames near curtains, foam, finishes or unknown air movement. Professional smoke tools and proper safety procedures provide better evidence.

What to Look for Behind Interior Trim

ENERGY STAR recommends checking the space between wall framing and the jamb when poor sealing is suspected. Common findings include empty gaps, loosely placed fiberglass, discontinuous foam and open connections to old weight pockets.

A window-and-door-rated low-expansion foam can insulate and air-seal many perimeter gaps when properly applied. Fiberglass alone may insulate but is not a dependable air barrier. Backer rod and sealant may suit other joint geometries.

Do not force insulation so tightly that the frame deflects. Test window operation after the repair cures and before casing is permanently reinstalled.

Do Not Fix an Air Complaint by Blocking Water Drainage

Window weeps and certain sill locations are designed to release water. Covering them with sealant or foam may appear to stop a localized draft while creating a hidden moisture problem.

Exterior caulk should be applied only at locations permitted by the window, trim and installation instructions. The concealed flashing system must continue to drain. Review Suburban Wholesale’s window flashing guide before adding material across an unfamiliar opening.

Match the Repair to the Evidence

For difficult product and installation questions, Suburban Wholesale offers professional consulting and product training seminars.

Document Before Opening a Warranty Claim

Record the window manufacturer, series, size, serial or order information, installation date, weather conditions, leakage location and tests performed. Photograph sash alignment, weatherstripping, locks, perimeter cavities and exterior details before altering them.

This evidence helps separate product service from installation correction. It also prevents a repair from destroying the very condition the manufacturer or contractor needed to evaluate.

Suburban Wholesale’s professional quoting service can help contractors maintain accurate product and option information during the ordering process.

Repair the Draft Without Damaging the Finish

Interior casing should be removed gradually, with paint joints cut first and mitered pieces protected. Older painted openings may trigger lead-safe requirements. Exterior trim and aluminum capping should not be bent open casually if it cannot be restored cleanly.

Plan access, repair and refinishing as one scope. A successful air-seal repair should leave consistent casing reveals, clean sealant lines and a window that operates freely.

Contractors and homeowners can examine operating windows, frame profiles and trim transitions during a Suburban Wholesale showroom visit.

The Bottom Line

A draft complaint is a symptom, not a diagnosis. Product leakage, installation gaps, wall leakage and cold-glass convection can feel similar. Test the operating window, perimeter and surrounding wall separately before assigning blame.

The fastest repair is not the one with the most caulk. It is the smallest evidence-based correction that fixes the actual path without obstructing drainage or distorting the window.