Foggy or condensation between panes - Written Fixed-Price Quotes, Permits Handled

Foggy or Condensation Between Panes

If you’re looking at a window right now and the fog is inside the glass – not on the surface you can wipe off – the seal on that insulated glass unit has failed. Moisture has gotten into the airspace between the panes, and it will not clear on its own. The fix is glass replacement, not cleaning.

Call (903) 354-7134

Insulated glass units (IGUs) are the sandwich of two or three panes of glass with a sealed airspace between them. That airspace is filled with argon or krypton gas at the factory, and it’s what gives the window its insulating value. A thin bead of sealant around the perimeter holds everything in. When that sealant cracks, shrinks, or separates – through age, sun exposure, or thermal cycling – outside air and humidity enter the cavity. The fog you’re seeing is that moisture condensing on the inner glass surfaces, where no cloth can reach it. The insulating gas is gone at that point, and so is a meaningful share of the window’s energy performance.

Why It Happens

Seal Failure from Thermal Cycling

Every window expands in heat and contracts in cold, thousands of times over its life. The sealant that bonds the panes together flexes with every cycle. Eventually it fatigues, and a small gap opens – enough for humid air to push in. You’ll usually notice this first on windows that get the most direct sun, because those units cycle through wider temperature swings each day. The fog tends to appear on warm mornings and partially clear by afternoon, at least early in the failure; once the seal is fully gone, the haze stays.

Sealant Degradation from UV Exposure

South-facing and west-facing windows take the most ultraviolet load. UV breaks down the polymer sealants used in IGUs over time, making them brittle before their thermal cycling even becomes an issue. If your fogged windows are the ones that catch the afternoon sun – what we think of as “west light” – UV degradation is a likely contributor. There’s no visual tell on the exterior, which is why homeowners are often surprised that a window that looks fine on the outside can be failing on the inside.

Faulty or Damaged Installation

A unit that wasn’t set level, was pinched in the frame during installation, or had its sealant nicked during handling can fail well before the end of its expected lifespan. If you have foggy panes on windows that were replaced or installed relatively recently – within five to ten years – installation quality is worth investigating. Look at whether the fogged units are isolated to one area of the house or scattered across multiple elevations; a cluster near one wall sometimes points back to a single installation job.

Frame Damage or Water Intrusion at the Glazing Bead

The glazing bead is the trim piece that holds the glass unit inside the frame. If water is getting behind it – through a cracked exterior caulk line, a failed frame corner weld, or physical damage to the sash – it can accelerate seal failure from the outside in. Run a finger around the interior perimeter of the affected sash. If the frame feels soft, painted-over water stains are visible at the corners, or the glazing bead is loose, you may have a frame problem alongside the glass problem. That changes what the repair looks like, and a technician will need to assess both.

What to Do Right Now

• Identify which panes are affected. Touch the interior glass surface. If the fog is on a surface you cannot reach – between the panes – it’s a failed IGU. If it wipes off, it’s normal condensation on the room-side surface, which is a humidity issue, not a seal failure. Knowing this before you call saves time.
• Photograph the window from the inside and outside. A clear photo of the fogged area, the frame corners, and the exterior caulk line gives your local Westlight Windows & Doors team useful information before they arrive. Take the photos in morning light when the haze is typically most visible.
• Note how many units are affected and where in the house they are. Count the windows and write down which direction they face. A pattern – all south-facing, all in one room, all from the same original installation – helps diagnose the root cause faster.
• Do not attempt to drill into or disassemble the glass unit yourself. Some online guides suggest drilling a small hole in the glass to let the moisture escape. This compromises the structural integrity of the pane, eliminates any remaining manufacturer warranty, and does not fix the underlying seal failure. Leave the glass alone.
• Check the exterior caulk around the affected frames. Look for cracks, gaps, or areas where the caulk has pulled away from the frame or the siding. If you see open gaps, note them but leave the repair to the technician – caulk work sounds simple, but done incorrectly it can trap moisture rather than exclude it.

How We Fix It

When your local Westlight Windows & Doors team arrives, the first thing they do is confirm which panes have failed and whether the frame itself is sound. Most of the time, a fogged window means a failed IGU, and the frame and hardware are still in good shape. In that case, the repair is glass-only: we order a new insulated glass unit to match the existing frame dimensions, remove the glazing bead, set the new unit, re-glaze, and reinstall the bead. For a straightforward same-sash glass replacement, most units are done in under two hours once the glass is on site.

If the frame is also compromised – rotted corners, warped sash, or water damage that has spread into the rough opening – the path is a full window replacement. We carry eight manufacturer lines, including energy-efficient ECO Window Systems, so we can match the right product to your home’s needs rather than fit your job to whatever we happen to stock.

Before any work starts, you receive a written price. That number does not change at the door. Every completed job is covered by our 365-Day Done Right Promise: if the work isn’t right within the guarantee period, we come back and correct it at no charge. A written copy of that guarantee goes home with you the day the job is done.

Frequently Asked Questions

Get It Fixed

Fogged glass doesn’t clear on its own, and the longer the frame sits wet, the bigger the job gets. Call (903) 354-7134 – a real person answers around the clock – or book online to schedule your free written estimate. Your local Westlight Windows & Doors team will diagnose the problem, give you a price in writing before any work starts, and back the repair with our 365-Day Done Right Promise.

Written by Owen Satterfield, Owner at Westlight Windows & Doors, part of the Kingswell network of independently owned and operated locations since 2009.