Is moisture between my exterior door panes a failed seal?

I’d separate the two diagnoses here. If the moisture is truly inside the sealed glass cavity, persistent fogging usually points to a failed insulated-glass seal. Inspecting the sill, caulk, sweep, and trim won’t fix or really confirm that failure; those checks are for water or air getting around the door frame.

A quick check is to view the panel from both sides and try wiping each glass surface. If the haze won’t wipe off from either accessible surface, or you can see droplets between the panes, the glass unit is the likely problem. If it wipes away, note which side it’s on: indoor condensation is more likely on the room-facing surface during humid conditions, while exterior condensation can occur when the outside pane is colder than the air.

Still inspect the sill and perimeter, since a leaking frame can create a separate issue. Look for staining, soft material, failed corner joints, blocked sill drainage, or water appearing after a hose test. Many entry doors use a replaceable insulated-glass panel or sash, so the whole door often doesn’t need replacement, but the exact replacement depends on the panel dimensions, thickness, and how it’s retained.

The wipe test gets tricky when a decorative grille or textured surface blocks access to the room-facing pane. Is there a reliable way to distinguish surface condensation from moisture between panes in that situation? For example, would viewing the panel at an angle with a flashlight reveal droplets or a haze inside the cavity, or is removing the grille usually necessary?

A flashlight can help, but it isn’t conclusive. Shine it across the glass at a shallow angle in dim light. Droplets or a diffuse haze that stays in the same plane as you change the viewing angle can suggest moisture in the cavity. Reflections from a grille or textured glass can look very similar, though.

Before removing the grille, compare the view from both sides and inspect the exposed edge of the glass. If you can see a continuous spacer or cavity edge around the panel, that’s useful evidence of where the haze is located. Grille removal is usually unnecessary for diagnosis and can damage snap-in retainers or disturb a seal. If the grille is integral to the glass unit, it won’t provide access anyway.

Photographing the panel from both sides can help more than the flashlight alone. Compare the haze with the visible spacer edge around the glass. Surface reflections and grille patterns shift as the viewing angle changes, while moisture inside the sealed unit stays aligned with the cavity and spacer. That can confirm the location without removing the grille or risking its retainers.

Photograph the same spot from the same angle as room conditions change.

- Lower indoor humidity for a day or two and note whether the haze changes as the room-facing glass warms or cools.
- Surface condensation often appears, clears, or shifts with changes in indoor humidity and glass temperature.
- Haze or droplets between the panes may remain in the same area, although their visibility can still change somewhat with temperature.

A flashlight and spacer-edge comparison can still help, but reflections through textured glass are easy to misread. If the haze stays aligned with the cavity and spacer edge through several changes in conditions, a failed insulated-glass seal becomes more likely without removing the grille.

Could the door maker use the door’s model or serial number to identify a compatible replacement panel? If not, a glass supplier may be able to match it from the panel details.