Wipes from the inside
Review indoor humidity, ventilation, coverings and surface temperature before ordering glass.
Hamilton Foggy Window Guide
Foggy Windows and Sealed Unit Replacement
Where the moisture sits matters: room-side condensation, exterior dew and haze trapped between panes point to different causes and remedies.
Locate the Moisture First
Not every cloudy window has a failed seal
Moisture that wipes from the room-side surface often relates to indoor humidity and glass surface temperature. Exterior dew can appear when an efficient outer pane cools below the outdoor dew point. Neither condition automatically means the insulated unit has failed.
Haze, droplets or mineral-like staining trapped inside the sealed cavity cannot be wiped from either exposed surface. That pattern is consistent with lost seal integrity and deserves an insulated-glass assessment.
A diagnosis should also consider nearby water staining, frame condition and whether the sash opens and locks normally.
The Wipe Test
Use moisture location to choose the next step
Do not drill, heat or chemically treat the unit before documenting it.
Forms on the exterior
Weather and radiative cooling can create temporary outside dew on otherwise serviceable glass.
Trapped between panes
Permanent internal haze supports a sealed-unit failure assessment when both exposed faces are clean.
Diagnosis Details
Questions homeowners ask about foggy thermopanes
Can a failed sealed unit be resealed in place?
A durable repair normally replaces the factory-sealed glass assembly. Surface sealant does not remove internal moisture or recreate the original cavity.
Will the fog disappear in warm weather?
It may change with temperature, but recurring internal haze indicates moisture remains in a cavity that is supposed to stay sealed.
Does a foggy unit stop insulating completely?
The window still separates indoors from outdoors, but seal loss can reduce the intended performance and permanently obstruct the view.
Can the frame stay?
Often, when the sash, glazing stops, drainage and frame are sound. The technician must confirm serviceability and final glass specifications.
What if several panes fail together?
Compare grouped reglazing with complete replacement, especially when operation, frame condition or visual matching also need attention.
Can new glass match exactly?
Current coatings, spacers and grids may look different from aged units. Review the closest practical match under daylight before ordering.
Glass-Only or Complete Window
Internal fog identifies the pane—not the full scope
The sealed unit is the isolated failure
Custom insulated glass can restore clarity while retaining a stable, operable frame.
- Moisture is between panes
- Sash is dry and square
- Stops and drainage are serviceable
Fogging overlaps with broader deterioration
Complete replacement may be more durable when several units, the frame and operation all need correction.
- Multiple connected failures
- Frame or sill damage
- Matching and parts are impractical
Avoid Cosmetic Shortcuts
Clarity requires replacing the sealed assembly
Drilling holes or adding vents can change the appearance temporarily but does not restore the original factory seal, gas fill or performance. Ask what the proposed method actually warrants.
For a useful quote, clean both exposed glass faces and send photos from several angles, plus the complete sash and any spacer markings.
Continue the Research
Read the next relevant guide
Foggy window assessment
Request a Repair AssessmentHave cloudy or foggy windows in Hamilton?
Clean the accessible glass, then send Windows Hamilton photos of the full window and internal haze. We will help distinguish sealed-unit replacement from humidity or broader frame concerns.
Talk with our team: Call Windows Hamilton at 289-975-4020.