Foggy Double-Pane Windows in Seattle: Repair or Replace?
If you've got a window that looks cloudy no matter how much you clean it, you're not alone. Foggy double-pane windows are common in Seattle-area homes, from older houses in the city to newer builds in Kirkland, Renton, and Everett. The good news is that a foggy window often doesn't mean you need a whole new window. Here's what's going on and what your options are.
First, Check Where the Fog Is
Not all window condensation is a problem. Try this simple test:
Wipe both sides of the glass. If the moisture comes off, it's surface condensation. It's caused by indoor humidity and temperature differences, and it doesn't mean the window has failed.
If you can't wipe it away, the moisture is trapped between the panes. That's the sign of a failed seal.
Surface condensation on the inside of the glass is common in cool, damp weather. Better ventilation, like running bath and kitchen fans, often helps.
What Causes Fog Between the Panes?
A double-pane window is really a sealed package called an insulated glass unit, or IGU. It's two panes of glass held apart by a spacer around the edge, with a sealed air or gas space in between. That sealed space is what makes the window insulate.
Inside the spacer is a desiccant, a drying material that soaks up small amounts of moisture. According to InterNACHI, the home inspectors' association, as the seal fails over time, more moist air gets into the space between the panes. Once the desiccant is saturated, it can't stop condensation anymore, and the window starts to fog [1]. Building research on insulating glass points to the daily cycle of heating, cooling, and pressure changes, which flexes and wears down the edge seal over time [2].
Things that can speed up seal failure:
Age
Strong sun exposure and heat
Water sitting against the bottom edge of the glass
Physical damage or a poor original installation
Why It Matters
A foggy window is more than an eyesore:
Your view is blocked, and it usually gets worse over time.
Insulation may drop. InterNACHI notes that a window with visible condensation between the panes has failed and needs to be repaired or replaced [1].
Mineral deposits can build up inside the unit and leave permanent staining.
Your Options: Defogging, Glass-Only Replacement, or a Full New Window
Defogging services
Some companies drill small holes, dry out the space, and reseal it. InterNACHI notes there's real debate about whether this actually restores the window or just hides the problem [1]. It doesn't restore the original sealed space, so we generally don't recommend it as a long-term fix.
Glass-only (IGU) replacement
For many homes, this is the sweet spot. Only the sealed glass unit is replaced. Your existing frame, sash, and trim stay in place. A new unit is made to the exact size, then installed in the existing frame.
Glass-only replacement usually makes sense when:
The frames are solid, square, and not rotting or warped
You like the look of your current windows
Only one or a few windows are foggy
You want to fix the problem without a larger project
Full window replacement
Sometimes the frame itself is the problem. A full replacement may be the better choice when:
Frames are rotted, cracked, or warped
Windows are drafty around the frame, not just the glass
Windows are hard to open, close, or lock
Many windows across the house are failing at once
You're already planning siding or exterior work
Since True View does window and door installation as well as glass work, we can look at both options and tell you honestly which one makes sense.
Is Your Window Under Warranty?
Before paying out of pocket, check your paperwork. Many window and glass manufacturers include a warranty against seal failure. Look for a label or etching in the corner of the glass, or find your original purchase documents.
A Note on Safety Glass
If the foggy window is in a door, next to a door, or near a tub or shower, building codes generally require safety glass in those locations [3]. A replacement unit needs to meet the same requirement, and a qualified glass installer will check this for you.
FAQ
Can I fix foggy windows myself?
Not really. The fog is inside a sealed unit, so cleaning won't reach it. The lasting fix is replacing the glass unit or the window.
Is foggy window repair cheaper than a new window?
Glass-only replacement usually costs less than a full new window because the frame and trim stay put, but it depends on size, glass type, and access. A free estimate will give you real numbers.
How long does IGU replacement take?
Each unit is made to order, so we measure first and install once the new glass arrives. The swap itself is usually quick.
Do you service areas outside Seattle?
Yes. We replace window glass throughout Seattle, Bellevue, Kirkland, Redmond, Renton, Kent, Tacoma, Everett, and nearby areas within about 25 miles.
Get a Clear View Again
True View LLC is a licensed, bonded, and insured Seattle glass and construction company (WA License TRUEVVL740KR). We'll take a look at your foggy windows and tell you whether glass-only replacement or a new window makes more sense. Estimates are free, and we reply to estimate requests within 24 hours. Call (206) 699-0604 or email project@trueviewnw.com.
Sources
InterNACHI, "Condensation in Double-Paned Windows." https://www.nachi.org/condensation-double-paned-windows.htm
Wolf, A.T., "Design and Material Selection Factors That Influence the Service-Life and Utility Value of Dual-Sealed Insulating Glass Units," CIB conference paper (PDF). https://www.irbnet.de/daten/iconda/CIB9944.pdf
International Residential Code Section R308.4, Hazardous Locations (summarized in Boulder County Publication B-30, "Safety Glazing"). https://bouldercounty.gov/property-and-land/land-use/building/building-publications/b30-safety-glazing/
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