What Causes Commercial Windows to Leak Air or Water?

Air and water leaks around commercial windows can create more than just discomfort. Over time, they can contribute to higher energy costs, interior damage, moisture problems, and repeated maintenance complaints. In many cases, the issue comes down to worn components, failed seals, or drainage problems rather than the entire window system.

1. Worn or Damaged Weatherstripping

Weatherstripping helps seal the gaps between moving window components. As it ages, it can compress, crack, shrink, or pull away from the frame, allowing outside air and moisture to pass through.

Replacing worn weatherstripping can often improve both comfort and energy efficiency without requiring major repairs.

2. Failed Sealants or Caulking

Sealant around the perimeter of the window helps keep water from entering between the frame and the surrounding wall system. Cracked, separated, or deteriorated caulking can create a direct path for water intrusion.

These areas should be inspected regularly, especially on older buildings or elevations exposed to heavy weather.

3. Clogged or Blocked Drainage Paths

Many commercial window systems are designed with weep holes or internal drainage channels that allow water to escape. Dirt, debris, or old sealant can block these paths and cause water to collect inside the frame.

Keeping drainage openings clear can help prevent water from backing up into the building.

4. Damaged Gaskets or Glazing Components

Gaskets and glazing seals help secure the glass and keep moisture out. Over time, these materials can shrink, crack, or become displaced.

When that happens, water or air may begin entering around the glass even if the frame itself is still in good condition.

5. Improper Operation or Hardware Problems

A window that does not close evenly may never fully seal. Worn hinges, operators, locks, balances, or other hardware can prevent the sash from seating correctly against the frame.

Correcting the hardware problem can sometimes restore the seal without replacing the window.

Finding the Source of the Leak

The visible location of a leak is not always where the problem begins. Water can travel through framing or wall cavities before appearing indoors, which is why proper inspection matters.

For commercial buildings, identifying the failed component early can help prevent minor leakage from becoming a larger repair project. Window Repair Systems can help evaluate existing window conditions and determine whether targeted repairs can restore proper performance.