As temperatures begin dropping around Fargo, it is common for homeowners to notice something they have not seen all summer, moisture collecting on the inside of their windows.
A little window condensation does not automatically mean there is something wrong with the window. In many cases, it has more to do with the temperature outside, the temperature of the glass, and the amount of moisture inside the home.
Understanding why it happens can help you determine whether you are seeing a normal seasonal condition or something worth looking into further.
Why Does Condensation Form on Windows?
Condensation forms when warm, moisture containing air comes into contact with a surface cold enough for that moisture to turn into liquid water.
During a Fargo winter, the inside surface of a window can become considerably colder than other surfaces in the home. If indoor humidity is high enough, moisture may begin collecting on the glass.
It is similar to the moisture that forms on the outside of a cold drink during the summer. The glass is not creating water. Moisture that was already in the surrounding air is condensing on the colder surface.
Why Does It Start Showing Up in the Fall?
Window condensation often becomes noticeable when outdoor temperatures begin falling but indoor humidity is still relatively high.
As fall turns into winter and temperatures continue to drop, the interior surface of the glass becomes colder. That means condensation can occur at lower indoor humidity levels.
This is one reason a window that remains dry during September might develop condensation during a cold stretch in January.
Does Window Condensation Mean the Windows Are Bad?
Not necessarily.
Window performance does matter. Older windows or windows with lower insulating values may have colder interior glass surfaces, making condensation more likely.
But even a good window can develop condensation when indoor humidity is high and outdoor temperatures are very low.
Before assuming the window needs replacement, it is worth considering the conditions inside the home.
Where Does Indoor Moisture Come From?
Normal daily activities add moisture to indoor air.
Common sources include:
• Cooking
• Showering and bathing
• Laundry
• Humidifiers
• Damp basements or crawlspaces
During warmer weather, this moisture may not be particularly noticeable. Once the house is closed up for heating season, however, moisture can accumulate more easily.
Pay Attention to Indoor Humidity
Indoor humidity that feels comfortable during mild weather may be too high during very cold weather.
There is not 1 humidity setting that works perfectly throughout an entire Fargo winter. As outdoor temperatures change, homeowners may need to adjust indoor humidity accordingly.
A simple indoor humidity meter can help you understand the conditions in your home.
If you use a whole house humidifier, pay attention to its setting as temperatures fall. Adding more humidity is not always better.
Ventilation Matters Too
Bathroom exhaust fans and kitchen exhaust systems can help remove moisture where it is produced.
Use bathroom exhaust fans while showering and allow them to continue operating afterward. When cooking produces significant moisture, use an exhaust fan that vents outdoors when available.
Homes vary considerably in how tightly they are constructed and how they are ventilated, so moisture behaves differently from 1 house to another.
What About Condensation Between the Glass?
This is different from condensation on the room side of a window.
Many modern windows contain insulated glass units made with multiple panes. If moisture or a persistent foggy appearance develops between those panes, the seal around the insulated glass unit may have failed.
Cleaning the interior or exterior surface will not remove condensation that is actually between the panes.
A failed glass seal does not necessarily mean the entire window needs immediate replacement, but it can reduce the insulating performance and affect visibility through the glass.
When Should Window Condensation Get Your Attention?
Occasional light condensation during very cold weather can occur in many homes.
More persistent moisture deserves attention, particularly when water regularly collects on window sills, trim, or surrounding wall surfaces.
Over time, repeated moisture can contribute to staining, deterioration of finishes, and other moisture related conditions.
The goal is not to panic when you see moisture on a window. The goal is to understand why it is occurring and manage the conditions contributing to it.
A Useful Winter Clue
Windows can tell you quite a bit about conditions inside a home.
As temperatures drop around Fargo, Moorhead, West Fargo, and surrounding communities, condensation may be an indication that indoor humidity needs some attention. It can also provide clues about window performance, ventilation, and moisture sources within the home.
If you notice condensation this fall or winter, start by looking at the bigger picture. Consider the outdoor temperature, indoor humidity, ventilation, and where the moisture is appearing.
Understanding those conditions is usually more useful than immediately assuming the window itself is the problem.
Nordic Inspections provides professional home inspections throughout the Fargo, Moorhead area and surrounding North Dakota and Minnesota communities. If you are purchasing a home and have questions about windows, moisture, ventilation, or other visible components of the home, these are some of the many areas evaluated as part of a home inspection.
Call or text us at 701-566-1446 ext. 0 to schedule an inspection.