How to Stop Condensation on Windows

Waking up to foggy, dripping windows is frustrating — and it’s more than just a cosmetic issue. Persistent window condensation can lead to mold, mildew, and damage to your window frames and walls.

The good news is that condensation on windows is usually fixable without expensive repairs. Understanding the cause is the first step.

Why Windows Get Condensation

Condensation happens when warm, moisture-laden air hits a cold surface. Your windows are often the coldest surface in a room, making them the perfect place for water vapor to condense.

Common sources of indoor moisture:

• Cooking and boiling water
• Showers and baths
• Drying clothes indoors
• Breathing (yes, really)
• Houseplants
• Gas appliances

How to Stop Condensation on Windows

1. Improve Ventilation

The simplest fix is to let moist air escape.

• Open windows for 10-15 minutes each morning, even in winter. Cross-ventilation (opening windows on opposite sides of the room) works best.
• Use extractor fans when cooking or showering — run them during and for 15 minutes after.
• Open trickle vents on your windows if they have them. These small vents allow continuous background ventilation without significant heat loss.
• Leave interior doors open to allow air circulation between rooms.
• Consider a whole-house ventilation system if condensation is a persistent problem across multiple rooms — mechanical ventilation with heat recovery (MVHR) is particularly effective in newer homes.

2. Use a Dehumidifier

A dehumidifier actively removes moisture from the air. There are two main types:

• Compressor dehumidifiers — best for warmer climates (above 15°C/59°F). More energy-efficient in moderate temperatures. Good all-rounders.
• Desiccant dehumidifiers — work better in cooler rooms (down to 1°C/34°F). More effective in unheated spaces like conservatories or garages.

How to use one effectively:

• Place it in the room with the worst condensation.
• Run it for 2-3 hours each morning, or continuously if humidity is very high.
• Empty the water tank regularly (or use the continuous drain hose if available).
• Target indoor humidity of 40-50% — this range prevents condensation without drying the air so much that it irritates skin and respiratory passages.

Budget tip: Even a small, inexpensive dehumidifier can make a noticeable difference in a bedroom or small room. Look for one with a humidistat so it maintains your target humidity automatically.

3. Stop Drying Clothes Indoors

Drying clothes on radiators or indoor racks releases large amounts of moisture into the air. A single load of washing can release 2-3 litres of water into your home.

• Dry clothes outside when possible.
• Use a ventilated indoor dryer in a room with an open window.
• Consider a clothes horse near an open window rather than on a radiator.
• If you must dry indoors, choose a room with good ventilation and a dehumidifier running.

4. Keep Heating Consistent

Fluctuating temperatures create condensation problems. When warm, moist air hits cold surfaces, condensation forms.

• Keep a low, consistent temperature rather than heating in bursts.
• A warm room with dry air has less condensation than a hot-and-cold cycle.
• Keep bedroom doors closed during the day and heat them slightly at night — a cold bedroom with warm, moist air from the rest of the house is a recipe for condensation.
• In older homes with single glazing, maintaining a slightly higher background temperature (16-18°C/61-64°F) can prevent surfaces from becoming cold enough for condensation.

5. Use Moisture Absorbers

For mild condensation issues, moisture-absorbing products can help.

• Place silica gel packets or commercial moisture absorbers on windowsills.
• Use a bowl of salt or baking soda as a natural alternative.
• Replace or recharge them regularly.
• These work best as a supplement to other methods, not as a standalone solution.

6. Check Your Window Seals

Faulty seals let cold air in and reduce the insulating barrier.

• Check for drafts around window frames — hold a candle near the edges and look for flickering.
• Replace worn or damaged weatherstripping.
• Apply window insulation film in winter for an extra barrier — this is cheap and easy to install.
• For older windows, consider secondary glazing as a more permanent alternative to window replacement.

7. Apply Anti-Condensation Coating

Special sprays create a thin layer that reduces surface tension, preventing water droplets from forming.

• Buy anti-condensation spray from hardware stores.
• Apply to clean, dry glass.
• Reapply every few weeks.
• This works by making water sheet off the glass rather than forming droplets — it’s effective but not a complete solution on its own.

When Condensation Is a Bigger Problem

If condensation appears between the panes of double-glazed windows, the seal has failed and the unit needs replacing. This is different from surface condensation and requires professional repair.

Signs of failed double-glazing seals:

• Condensation or misting between the glass panes
• Visible moisture droplets inside the sealed unit
• A cloudy or foggy appearance that doesn’t clear when you wipe the glass

This is a common issue with older double-glazed units (typically 10-15+ years old) and is usually more cost-effective to repair than to replace the entire window.

Quick Fixes vs. Long-Term Solutions

Climate Considerations

Condensation is more common and harder to control in certain climates:

• Cold, humid climates (UK, Pacific Northwest, coastal areas) — condensation is almost inevitable in winter without good ventilation and heating. Focus on dehumidifiers and consistent heating.
• Hot, humid climates — air conditioning is your best dehumidifier. Ensure AC units are properly maintained and not set too cold (which can cause condensation on the cold side of windows).
• Dry, cold climates — condensation is less common but can still occur, especially in tightly sealed modern homes with poor ventilation.

The Bottom Line

The most effective approach combines better ventilation with moisture control. Open windows daily, use extractor fans, and consider a dehumidifier if condensation is persistent.

Most condensation problems can be solved without replacing windows — it’s about managing the moisture in your home, not upgrading your glazing. If condensation persists despite these measures, it may be worth having a professional assess your home’s ventilation system.

Related Guides

• How to remove mold from your home — condensation creates the damp conditions mold thrives in.