Condensation and frost on Des Moines windows
When the January low averages 14 degrees at the airport (NOAA normals), the inside of a window glass gets cold, and warm indoor air drops its moisture there. Some condensation is normal. Fog between the panes, or ice on the inside every night, is not.
Three kinds of moisture
- On the inside of the glass. Indoor humidity is meeting cold glass. Common on cold mornings, worst on single-pane windows and in bathrooms and kitchens.
- Between the panes. The seal on the insulated glass unit has failed. It will not wipe off and will not clear up. The glass unit needs replacing. Glass repair.
- On the outside. Usually on cool mornings in spring and fall. It means the glass is insulating well enough that the outer pane stays cold.
Average low and high by month, Des Moines (degrees F)
What to try first
- Run bath and kitchen exhaust fans, and check that they vent outside.
- Lower indoor humidity in deep cold, for example with a humidifier set lower.
- Open blinds and curtains so room air reaches the glass.
- Check weatherstripping and storm windows on older windows.
When it points to replacement
Frost inside most windows every cold night is a sign the windows are not keeping up with a Des Moines winter. So is rot in the sills, and so are failed seals on several units. U-factor measures the rate of heat transfer and tells you how well the window insulates. Lower is better. What to look for in a new window.
Questions Des Moines homeowners ask
Is condensation on new windows a defect?
Usually not. Tighter new windows can keep more moisture in the house, and warmer glass still fogs at the edges when indoor humidity is high. Fog between the panes on a new window is a seal failure and a warranty question.
Can a foggy window be cleaned between the panes?
Some services drill and dry the unit, but the seal is still broken. Replacing the insulated glass unit is the usual fix.