Window condensation: what to record before replacing a window

Questions covered in this guide

Start by locating the moisture

Andersen’s guidance distinguishes room-side condensation, outdoor dew and condensation between the panes of an insulated glass unit. Outdoor dew alone is not evidence that a window has failed. Moisture between sealed panes can indicate a seal problem. These observations help frame a service request; they do not identify every cause of water around an opening.

Make a short observation record

Choose a safe place indoors and note the room, date and approximate time. Describe whether the moisture can be wiped from the room-side glass or appears beyond it. Take an ordinary photograph if useful. Record whether the problem appears after rain, during cold weather or at another repeatable time. Do not reach outside an upper-floor opening or dismantle the window to determine its location.

Ask what needs to be repaired

Give the record to an installer or manufacturer service representative. Ask whether the assessment concerns the glass unit, sash, frame, installation or indoor conditions, and what further inspection supports that conclusion. Request any available repair option alongside a replacement proposal. Check the actual warranty and documentation before assuming either that a repair is covered or that an entire opening must be replaced.

Keep the quote matched to the diagnosis

Use a separate row for diagnosis, proposed work, retained components, finishing and warranty responsibility. If one quote replaces a component and another rebuilds the opening, compare those scopes explicitly. Our calculator prices replacement-window scenarios and cannot diagnose condensation or estimate a glass-only repair from a photograph. If replacement is recommended, count only the openings in that proposed project. Save your observations with the quote so the work can be checked against the reason you requested it.

Putting it into practice

A location-and-timing record separates an observation from a diagnosis. Comparing component repair with whole-opening replacement avoids treating two different proposed remedies as equal products.

Sources and supported claims

Andersen distinguishes interior, exterior and between-pane condensation; exterior dew alone does not show window failure.
Source ↗ · national · Checked 2026-10-12

Andersen identifies condensation between sealed panes as a sign of seal failure; the specific repair scope still requires assessment.
Source ↗ · national · Checked 2026-10-12