How to stop condensation on windows, morning and night

Published by Aurala Naturals. Last updated 12 November 2026.

You stop condensation on windows by lowering the moisture in the room and moving the air, so warm indoor air does not sit on cold glass. Open the window for a short time each morning, run exhaust fans when you cook and shower, dry washing outside, and wipe the glass and sill dry. A dehumidifier can help in a closed room, but the first job is the moisture and the air.

This page is about stopping the water on the glass. For whether a dehumidifier belongs in a damp room at all, see a dehumidifier for mould. For the wider moisture picture, see damp versus mould.

Wipe the mould off, then run the Protection Kit in the room where it grows: the Waterless Diffuser plus First Light, six essential oils in the air. Lab tested: 99.2% on direct contact.

Why windows sweat

Air holds water vapour. Warm air holds more than cold air. When room air touches glass that is colder than its dew point, the water comes out as droplets on the glass. More detail: condensation, dew point and mould.

Bedrooms get it worst because two people breathing all night in a closed room add moisture, and the glass is coldest at dawn. Single glass in aluminium frames gets colder than double glazing.

Quick fixes you can do today

• Wipe the glass and the track every morning with a squeegee or microfibre cloth. Wring it out in the sink, not back into the track.
• Open the window or door for 10 to 15 minutes in the morning to swap the damp air out.
• Open curtains and blinds in the day. Closed curtains trap cold, wet air against the glass.
• Run the exhaust fan while you shower and cook, and after.
• Dry washing outside or in a vented dryer, not on a clothes horse in the bedroom.
• Leave a small gap open overnight if it is safe and secure to do so.

Longer-term fixes

• Run a dehumidifier in the closed room overnight. See dehumidifier for mould.
• Fix or add exhaust fans in the bathroom, kitchen and laundry, ducted outside, not into the roof space.
• Upgrade glazing to double glazing, or add a secondary glazing or window film made for insulation. Get a quote from a glazier. In a rental, ask the landlord in writing.
• Keep heating steady in winter rather than short bursts, if you heat the room.

Hold the room after you dry it: Protection Kit, from A$79.98

The Protection Kit is our Waterless Diffuser with one, two or three bottles of First Light. The diffuser has no water tank, so it adds no water to a room that already fogs its windows. An ultrasonic water diffuser would add more.

First Light is a six-oil blend of clove, litsea cubeba, tea tree, eucalyptus, peppermint and cedarwood. Lab tested: 99.2% on direct contact. See the lab test. See the lab method. It does not stop condensation and does not lower humidity. It is the daily routine for the room once the window, sill and seals are clean and dry.

Get the Protection Kit | Already own a waterless diffuser? First Light, A$39.99. Free standard shipping on Australian orders, with no minimum spend.

Clean the sill and track

If water has sat on the sill for weeks, you will see black or grey spots in the corners, the track and the rubber seal.

1. Wear gloves, eye protection and a fitted P2 or N95 mask, as the Australian CDC advises.
2. Vacuum loose dirt out of the track with a crevice tool.
3. Spray 4 parts white vinegar to 1 part water (CDC ratio) on the track, sill and seal. Let it sit for about 10 minutes, then wipe.
4. Use an old toothbrush in the corners of the track, then rinse it.
5. Dry everything with a towel.

Painted timber sills that are soft or swollen need repair. Full guide: mould on window sills and frames. Curtains with mould spots: wash them hot or replace them.

A morning routine for sweating windows

Use the diffuser in a ventilated room and keep the unit and the bottle out of reach. Directions: how to use and product use and safety.

Dry the window. Clean the track. Hold the room.

Condensation is a moisture problem, so fix the moisture first. Then keep the room on a daily routine that adds no water.

Get the Protection Kit, from A$79.98 or add First Light to your own waterless diffuser, A$39.99.

Condensation is a ventilation problem first. See does poor ventilation cause mould?

FAQ

How can you stop condensation on windows?

Lower the moisture in the room and keep air moving. Open windows for 10 to 15 minutes each morning, run exhaust fans, dry washing outside, open curtains in the day and run a dehumidifier in a closed damp room. Long term, double or secondary glazing keeps the glass warmer.

Why are my windows wet on the inside in the morning?

Warm, moist air from breathing, showers and cooking meets glass that cooled overnight. The water vapour turns to droplets on the cold glass.

Is condensation on windows bad?

Water that sits on the sill, track and seals every day keeps them damp, and damp surfaces can grow mould. Wipe it off each morning.

How do I clean mould off a window track?

Wear gloves, eye protection and a mask. Vacuum the track, spray 4 parts white vinegar to 1 part water, let it sit, scrub the corners, wipe and dry.

Should I run a diffuser near wet windows?

Yes, a waterless one. It adds no water to the room. Run First Light in it every day once the window and sill are clean and dry.

Related guides

• Damp versus mould in an Australian house
• How to reduce humidity in a room
• Mould on curtains and blinds
• The Protection Kit

Ready to stop the mould coming back in the room where it grows? Get the Protection Kit, the Waterless Diffuser plus First Light, from A$79.98 with free shipping Australia-wide. Lab tested: 99.2% on direct contact.