Exterior condensation on new windows is normal and means they are working. Interior condensation is a humidity issue. A draft at the trim rather than the sash is an installation problem. Sticking sash in the first weeks is usually adjustment, not defect.
New windows sometimes behave in ways that worry people, and the reaction is usually either to accept a real defect or to worry about something completely normal.
Here is how to tell which is which, and who is responsible for each.
Five things people report, and what they mean
| Symptom | What it usually is | Whose problem |
|---|---|---|
| Condensation on the outside glass | The window working correctly | Nobody, this is good |
| Condensation on the inside glass | Indoor humidity too high | Yours, adjust humidity |
| Draft at the sash edge | Weatherstrip or adjustment | Installer, warranty visit |
| Draft at the trim or wall | Perimeter not insulated properly | Installer, installation defect |
| Sash sticks or is stiff | Adjustment, or paint on the track | Installer, usually a quick fix |
| Visible gap at the trim | Trim work, or frame shifted | Installer |
| Lock does not align | Unit not set square | Installer |
| Fog between panes on a new unit | Defective glass unit | Manufacturer, via installer |
Exterior condensation is a good sign
This surprises people every autumn. Dew forms on the outside of a new window on cool mornings for the same reason it forms on a car windshield: the glass surface has dropped below the dew point of the outdoor air. On an old inefficient window, heat escaping from inside keeps the exterior glass warm enough that dew does not form. On a good new window, much less heat escapes, so the exterior glass stays cold and collects dew. It clears as the sun comes up. It is evidence the window is performing, not a defect, and it is more common on higher-performing units, which makes it counterintuitive.
How to tell a draft from cold glass
They feel similar and they are completely different problems. Hold a lit incense stick or a strip of tissue near the window on a windy day and watch. If it moves, air is leaking and the question is where: movement at the sash means weatherstripping or adjustment, movement at the trim means the perimeter gap between the frame and the rough opening was not properly insulated, which is an installation defect. If nothing moves but the area still feels cold and uncomfortable, that is convection off cold glass, not a leak. Air near the glass cools, becomes denser, and falls across the floor. That is a function of the glass performance, not the installation, and it is a reason to have specified better glass rather than a fault to be fixed.
What to do about it
- Call the installer first, regardless of whether you think it is product or installation. They should diagnose it and handle the manufacturer claim if it is product.
- Do it inside the workmanship warranty period, which is why you asked for that term in years before signing.
- Photograph the symptom, including where the moisture or gap is and in what conditions it appears.
- Note the conditions: outdoor temperature, wind direction, indoor humidity if you have a hygrometer.
- Do not attempt to re-caulk a suspected perimeter leak yourself before the installer has seen it, because it obscures the diagnosis.
- For interior condensation, try lowering indoor humidity for a week before calling. It is frequently the whole answer.
Ranges reflect typical Capital Region projects and are for planning only. Every Sundog quote is written, itemized, and free.
Frequently asked questions
Why do my new windows have condensation on the outside?
Because they are working. Less heat escapes through an efficient window, so the exterior glass surface stays colder and drops below the outdoor dew point on cool mornings, collecting dew. It clears with the sun. It is more common on better performing windows, which makes it feel like a defect when it is the opposite.
My new windows are drafty. Is that a defect?
Find out where the air is moving first. At the sash means weatherstripping or adjustment, which the installer should fix. At the trim or wall means the perimeter was not properly insulated, which is a genuine installation defect. No air movement but a cold feeling is convection off cold glass, which is about the glass specification rather than the install.
How long should new windows take to settle in?
They should work correctly on day one. There is no legitimate break-in period. If a sash is stiff or a lock does not align in the first week, call. Adjustment is quick and free inside the warranty, and a unit that is not set square will not improve on its own.
Should I caulk around my new windows myself?
Not before the installer has inspected a suspected leak, because fresh caulk over a perimeter gap hides the actual problem and can complicate a warranty claim. If the exterior caulk joint has a genuine gap after a year or two of settling, that is normal maintenance and fine to address.
My new window fogged up between the panes. What now?
That is a defective insulated glass unit and it is covered under the manufacturer warranty, which on a new window will be well within term. Call the installer, who should file and manage the claim. A new unit fogging is uncommon and not something you should accept as normal.
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