How to tell if your phone has internal water damage
When most people think of internal water damage, they picture a smartphone submerged in a sink, but for a Master Glazier, internal water damage represents a catastrophic failure of the Insulated Glass Unit or IGU. Much like the delicate circuitry of a mobile device, the space between your window panes is a controlled environment that must remain hermetically sealed to function. If you are seeing moisture where it should not be, you are witnessing a breach in the physical envelope of your home.
The Condensation Crisis: A Diagnostic Reality Check
A homeowner called me in a panic because their new windows were sweating. I walked in with my hygrometer and showed them the humidity was 60 percent. It was not the windows; it was their lifestyle choices, specifically a lack of ventilation in a tightly sealed building envelope. This is the first lesson in glass diagnostics: you must distinguish between surface condensation and internal seal failure. If the moisture is on Surface 1 (the exterior) or Surface 4 (the interior), your glass is likely doing its job. If the moisture is between the panes, your window has what we call internal water damage, or more accurately, a blown seal.
“Installation is just as critical as the window performance itself. A high-performance window installed poorly will fail.” AAMA Installation Masters Guide
The Anatomy of the IGU and Why It Fails
An IGU consists of two or more lites of glass separated by a spacer bar and sealed into a single unit. This cavity is often filled with Argon or Krypton gas to improve the U-Factor, which is the measure of non-solar heat flow. In our northern climate, where the temperature differential between the interior and exterior can reach 80 degrees, the glass undergoes constant thermal pumping. The air inside expands and contracts, putting immense pressure on the primary and secondary seals. When you search for a glass installer or mobile service for chip repair, you are often looking for a quick fix, but a chip in the glass can actually be the catalyst for a total seal breach. A small chip repair might save the structural integrity of the pane, but if that chip has allowed even a microscopic amount of gas to escape, the thermal efficiency of the unit is compromised forever.
The Role of the Molecular Sieve
Inside the spacer bar of every modern window is a desiccant, often a molecular sieve or silica gel. This material is designed to adsorb any residual moisture trapped during the manufacturing process. However, this desiccant has a finite capacity. Once it reaches its saturation point, the moisture has nowhere to go but onto the glass surface. This is the “fogging” people see. It starts as a faint haze, often only visible when the sun hits the window at a specific angle, but eventually, it leads to permanent calcium deposits or glass swiping. At this point, no amount of same-day mobile service can clean the interior; the unit must be replaced.
The Installation Autopsy: Why Flashing and Sill Pans Matter
In my 25 years of experience, I have seen that the most common cause of internal water damage is not the glass itself, but a failure of the surrounding water management system. If a window is not installed with a proper Sill Pan or integrated Flashing Tape, water will eventually find its way into the Rough Opening. Once water sits against the bottom rail of a wood sash or a vinyl frame, it begins to rot the secondary seal of the IGU from the outside in. We call this the Shingle Principle: every layer of the building must shed water to the layer below it and eventually to the exterior. When an installer skips the drip cap or fails to use a proper shim to level the sill, they are inviting water to pool against the glazing bead.
“The flashing system shall be designed to prevent water from entering the wall cavity or the interior of the building.” ASTM E2112 Standard Practice
Technical Indicators of Seal Failure
To determine if your window has internal moisture issues, you can perform a simple diagnostic. Use a high-lumen flashlight and hold it at a 45 degree angle to the glass. If you see iridescent streaks or a rainbow effect, that is a sign of oil film contamination from a failing butyl seal. Another sign is the presence of “white rust” or oxidation on the spacer bar. This indicates that the Argon gas has leaked out and been replaced by ambient air and moisture. In cold climates, a low U-Factor is king, and losing that gas fill means your heater is working twice as hard to combat the radiant cold coming off the glass. While a mobile service might offer a quick chip repair for a small crack, they cannot re-gas a window in the field. Total replacement of the IGU is the only way to restore the thermal performance of the opening.
Managing the Rough Opening
When we talk about a Rough Opening, we are talking about the tolerance of the hole in the wall. If the window is forced into an opening that is too small without enough room for a proper shim, the frame will bow. This bowing puts torque on the glass, which can lead to stress cracks or the gradual pulling away of the glazing bead from the glass surface. This creates a direct path for moisture to enter the glazing pocket. A professional glass installer knows that a window needs room to breathe and move. If you have an operable sash that is sticking, it might not be a hardware issue; it could be frame deformation that is slowly killing your glass seals. In the end, water management is a science, not an afterthought. You cannot simply caulk your way out of a poor installation. If the sill pan is missing, the window is on a countdown to failure.
