How to Prevent Condensation on Windows and Glass Panels

Home Care · 2025

Read time: ~6 mins · Updated: 12 Oct 2025

Condensation on glass is one of the most common problems UK homeowners face — especially during colder months.
It can cause damp smells, mould growth, and even damage to window frames.
Understanding why condensation happens and how to prevent it can help protect your property and keep your home comfortable all year round.

What causes condensation?

Condensation forms when warm, moist indoor air meets a cooler glass surface. The temperature difference causes moisture in the air to turn into droplets on the glass. This is more noticeable in winter when indoor heating raises humidity and windows become colder.

Types of condensation on glass

• Interior condensation – appears on the inside of windows due to excess indoor humidity.
• Exterior condensation – forms outside the window, usually harmless and a sign of good insulation.
• Between glass panes – indicates a failed seal in double or triple glazing, allowing moisture into the cavity.

Practical ways to prevent condensation

Condensation can be managed through a few simple adjustments in ventilation, heating, and glass choice:

• Improve ventilation: Use extractor fans in kitchens and bathrooms or open trickle vents to allow moisture to escape.
• Maintain steady temperatures: Keep indoor temperatures consistent — sudden cooling can trigger condensation.
• Use a dehumidifier: Reduces indoor humidity in winter months.
• Keep window sills clear: Avoid blocking airflow with curtains or furniture.
• Wipe glass regularly: Prevents moisture from turning into mould or staining.

When to upgrade your windows

If condensation appears between glass panes, the seal has likely failed. In such cases, the most effective solution is replacing the glazing unit with a modern insulated version. Upgrading to double or triple glazing with tempered safety glass can reduce condensation and enhance thermal performance.

• Choose units with warm-edge spacers and argon gas filling.
• Consider Low-E coatings to keep the inner pane warmer.
• Seal edges professionally to prevent moisture infiltration.

Frequently Asked Questions

Why do my new double-glazed windows still get condensation?
Even with modern glazing, poor ventilation or high humidity can cause internal condensation. The glass itself may not be faulty.

Can condensation damage window frames?
Yes. Persistent moisture can cause timber frames to rot and lead to mould or peeling paint on uPVC frames if not managed.

Is condensation between panes fixable?
No — once the seal is broken, the unit must be replaced. Modern tempered glass units with warm-edge spacers prevent this issue.

Does opening windows help?
Absolutely. Regular ventilation is one of the easiest and most effective ways to prevent condensation buildup indoors.

References:
GreenMatch UK,
Energy Saving Trust,
Homebuilding & Renovating