Condensation on Window

Condensation forms on a glass surface when that surface becomes cold enough for water vapour in the surrounding air to condense. Seeing droplets therefore does not automatically mean the window is faulty.

The first step is to establish which surface the moisture is on. Condensation on the room-side surface, on the exterior surface, and moisture trapped between panes are three different situations.

Why does condensation form on the room side?

The risk increases when the temperature of the inner glass surface is low in relation to the temperature and humidity of the indoor air. Indoor conditions, glass-surface temperature and air exchange can therefore all matter.

Everyday activities such as cooking, bathing, drying laundry and simply occupying a room add moisture to indoor air. When moisture production is high and removal is insufficient, conditions favourable to condensation on cooler surfaces are easier to reach.

Does condensation mean there is a ventilation problem?

It can indicate that air exchange is insufficient for the amount of moisture being produced, but the cause should not be diagnosed from droplets alone. Room temperature and glass-surface temperature also influence condensation.

If the windows have trickle vents, it is worth checking that they are not covered or dirty and that they are being used as intended. Assessing the building's complete ventilation system, however, goes beyond window servicing alone.

Is exterior condensation a fault?

Not necessarily. Under certain conditions, the exterior surface of well-insulating glazing can cool below the dew point and temporary condensation can form. It may be particularly noticeable in the morning and can disappear as the glass warms.

Exterior condensation by itself is not enough to conclude that the glazing unit or the whole window is defective.

What if the moisture is between the panes?

That is different from condensation on an accessible surface. If fog or droplets are inside the sealed cavity and cannot be wiped from either side, the glazing unit's seal integrity should be checked.

This symptom is covered in more detail on our Condensation Between Panes page. If assessment shows that glazing-unit replacement is appropriate, the service scope is described on our Glass Unit Replacement page.

How do we diagnose surface condensation?

We first establish where the condensation is: the room-side surface, exterior surface or between the panes. We check the condition of the window and components relevant to its operation, and for room-side condensation we also ask about the conditions in which it appears.

We do not assume in advance that gasket replacement, adjustment or a trickle vent is required. Any window-related work should follow the cause actually identified.

What can you check yourself?

• Where the condensation is – check whether the droplets can be wiped from the room side or exterior.
• When it appears – note whether it follows bathing, cooking or drying laundry, or appears mainly in the morning.
• User-accessible ventilation – if trickle vents are fitted, check that they are not covered or dirty, and make sure ventilation grilles are not obstructed.
• Humidity and temperature – a hygrometer and thermometer can help you observe indoor conditions, but a single reading does not by itself identify the cause.

There is no need to adjust the hardware or perform improvised airtightness tests simply because condensation appears on the glass.

What solution may be appropriate?

If indoor conditions are the cause, useful measures may involve reducing moisture sources, improving air exchange, or changing how the room is heated and used. If assessment identifies a fault in the window itself, we select the service appropriate to its cause.

A window trickle vent can support air supply where it forms part of the intended ventilation system, but it is not a universal solution for every case of window condensation.

Brands we work with

Regardless of the window or door manufacturer, we most often service wear-and-tear components that naturally degrade over time.

• VEKA, Salamander, Aluplast, Rehau – European PVC systems, among the most commonly found in Polish residential construction.
• Drutex, Oknoplast, MS Więcbork – Polish manufacturers found in newer residential developments.
• Schüco, Aluprof – aluminium windows and HST patio doors used in modern construction.
• Roto, Winkhaus, Maco, Siegenia – manufacturers of hardware and multi-point locking systems.
• Velux, Fakro – roof windows commonly installed in detached houses.

We use original spare parts or high-quality replacements — depending on the manufacturer and component availability.

How does our service work?

The service process is simple and transparent — six steps from first contact to warranty:

• Contact – fill in a short form or call us. We call back within approximately 15 minutes.
• Free on-site diagnostics – a technician arrives at the agreed time and assesses the condition on site.
• We explain the cause – we show you exactly what needs to be repaired.
• We present the cost – after diagnostics we provide an exact quote. No hidden fees.
• We carry out the repair – after your approval we complete the work, most often during the same visit.
• You verify the result – we test the outcome together. You receive a service report, a warranty on the work performed, and the manufacturer's warranty on original parts.

Where do we diagnose window-condensation problems?

We serve Warsaw, Krakow, Katowice and other regions covered by our service. You can check current coverage on our Cities page.

How much does it cost to address the cause?

The cost depends on whether window-related work is required and on its scope. Diagnostics and the technician call-out for assessment are free. If we propose paid work, we provide a quote for approval before it begins.

You can find indicative service prices on our pricing page.