Fogging between the panes of a double-pane window is not a cleaning problem. Wiping the glass does not fix it. Opening the window does not fix it. The fog is sealed inside the unit itself, between two pieces of glass that were never meant to be opened, and once moisture gets in there the only way it leaves is if the glass unit is replaced.
That much is fairly clear. What is less clear is whether you replace just the glass unit, the entire window, or whether the fogging you are seeing is even that problem at all. Not every cloudy mobile home window has a failed seal. Some of what looks like fogging is exterior condensation, which is actually a sign the window is working. This guide helps you tell the difference and make the right call.
Before spending anything, figure out which of these you are looking at.
This happens when humid outdoor air hits glass that is cooler than the dew point. It looks like fogging but wipes off from the outside and clears within an hour as the morning warms up. If your window looks foggy at 7am and clear by 9am, this is what you have. It actually means the window is doing its job. The interior glass is staying cold, which means the insulation is working.
This one collects on the interior face of the glass during cold weather and is a humidity problem inside the home, not a window problem. Mobile homes have relatively little air exchange compared to site-built construction, and when indoor humidity is high, moisture condenses on the coldest surface in the room, usually the window glass. Running a dehumidifier or improving ventilation resolves it. Replacing the window does not.
This is seal failure. The insulated glass unit has a hermetic seal around its perimeter that keeps the argon or air fill between the panes dry. When that seal breaks, humid air enters, moisture condenses on the inner glass surfaces, and because there is no way for it to escape, it stays. The fogging is permanent and gets worse over time as more moisture enters.
Quick test: is it seal failure or surface condensation? Run your hand across both sides of the glass. If the fog is on a surface you can touch, it is condensation. If the glass feels completely dry on both sides but the fogging is visible inside the unit, the seal has failed internally.
Mobile homes move more than site-built homes do. The structure is lighter, the wall cavities are shallower, and the whole assembly responds more noticeably to temperature swings and ground movement. That constant micro-movement stresses the perimeter seal of a double-pane unit more than the same window would experience in a conventional home.
“Thermal cycling is the primary cause of insulated glass unit seal failure. Repeated expansion and contraction of the spacer bar and sealant eventually allows moisture infiltration, typically after 10 to 20 years of service.”
— National Glass Association
Aluminum frames compound this. Aluminum expands and contracts at a different rate than the glass it holds, which puts additional stress on the sealant bead around the IGU perimeter. Vinyl frames handle thermal movement more compatibly with the glass, which is one of the practical reasons Low-E vinyl windows tend to last longer in mobile home applications than original aluminum units.
The U.S. Department of Energy notes that double-pane Low-E windows reduce heat transfer through the glass by 30 to 50 percent compared to standard double-pane units, which is relevant when you are deciding whether to repair or upgrade.
This is where most people get stuck. The glass unit itself is replaceable as a component. You do not always need to replace the entire window frame. But whether that makes sense depends entirely on what condition the frame is in.
• The aluminum or vinyl frame closes flush and latches correctly
• No rot, soft spots, or water staining at the frame corners or along the sill
• The frame has not separated from the wall — if it has, that is a separate problem covered in cold air coming through mobile home window
• The window is less than 15 years old and has had no previous repairs
• You find visible corrosion, soft corners, or mobile home window frame rot that compromises the structure.
• The frame has warped enough to cause a stuck mobile home window that will not close or latch properly.
• Multiple panes in the same window have failed, suggesting the frame is past its service life
• The home has had ongoing water infiltration around that opening
• The existing window is single-pane aluminum and the fogging question has prompted you to consider upgrading to double-pane
You will never see mobile home window condensation between glass on a single-pane aluminum window because there is no second pane to trap the moisture. If you have single-pane aluminum windows and they appear cloudy, it is usually surface contamination, oxidation on the aluminum frame, or worn screen mesh creating a visual effect. Cleaning the glass and frame usually resolves it.
For a broader breakdown of repair, replacement, and structural issues across manufactured homes, see our mobile home window and door problems guide.
What About Cracked or Broken Glass?
A cracked single-pane window can often be repaired inexpensively without touching the frame. Cut-to-size glass from a local glass shop, silicone adhesive, and an hour of work handles most cracks that have not reached the frame edge.
A crack that runs to the edge of the frame compromises the frame’s structural connection to the glass and the repair does not hold well. Full glass unit replacement is the cleaner fix. On a double-pane window, any crack that breaches the outer pane allows moisture into the space between the panes and the fog will follow within a season.
Before ordering any replacement window for a bedroom, check the opening size. Under HUD 24 CFR Part 3280, bedroom windows in mobile homes must provide a minimum 5.7 square feet of net clear opening for emergency egress. This is a fire escape requirement.
“Manufactured homes must comply with HUD Manufactured Home Construction and Safety Standards, including minimum egress requirements for sleeping rooms. Replacement windows must maintain compliance with these standards.”
— U.S. Department of Housing and Urban Development
The egress requirement is in Section 3280.404 of the HUD Manufactured Home Construction and Safety Standards (24 CFR Part 3280). Every window sold by American Supply and Air Products meets these standards.
A replacement window that is smaller than the original, or a window placed into a modified opening, may fall below the egress threshold. This affects insurance coverage and financing eligibility on the home. The HUD manufactured housing standards are publicly available and the egress requirement is in Section 3280.404. Every window sold by American Supply and Air Products meets these standards but a window from a general supplier may not.
Two measurements matter before any window goes on order. The rough opening dimensions (width and height of the stud-to-stud hole in the wall) and the wall depth. Mobile home walls run between 3 and 4.5 inches deep. A replacement window built for standard residential framing sits either proud of the wall or leaves exposed framing around the edges.
Measure three times across each dimension and use the smallest number. Mobile home rough openings are not always perfectly uniform, especially on older homes where windows, trim, and other mobile home parts may have been replaced over time
Windows are non-returnable once shipped. Confirm rough opening dimensions and wall depth before placing any order. If the opening is a non-standard size or the wall depth is unclear, call us first. Full details: returns and refunds policy.
Vinyl and aluminum replacement windows sized to mobile home rough openings and wall depths: mobile home windows. For homes where the frame is intact and the only issue is single-pane glass conducting cold, mobile home storm windows are a lower-cost alternative that installs inside the existing frame without removing it.
Describe what you have and we will tell you whether repair or replacement makes more sense. Our staff has matched mobile home windows to specific models and years since 1994.
Call 1-800-368-6208 | Mon-Fri 8am-5pm | Sat 9am-1pm
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Windows are non-returnable once shipped. Confirm your rough opening size before ordering.
Browse all mobile home parts at American Supply and Air Products, or call 1-800-368-6208.
