How to Stop Condensation on Windows: Humidity and Airflow Fixes That Work

Why Condensation Forms on Windows

Condensation forms when warm, moist indoor air touches a cooler surface, like glass. The air cools down and can no longer hold as much moisture, so water droplets appear on the surface. This is similar to a cold drink sweating on a hot day.

In homes, this usually shows up on windows because glass cools faster than walls. When outdoor temperatures drop, the inside surface of the window becomes cooler than the room air, and moisture collects there.

Key ingredients for window condensation

• High indoor humidity – too much moisture from cooking, showering, drying clothes indoors, or even normal breathing and plants.
• Cool window surfaces – older or poorly insulated windows, or strong temperature differences between inside and outside.
• Poor airflow – still air around the window that allows moisture to build up on the glass.

To stop condensation, you can either lower the humidity, warm up the glass surface, improve airflow across the window, or ideally, do a combination of all three.

Is Your Window Condensation Normal or a Problem?

Not all condensation is a sign of trouble. A small amount on very cold mornings, especially near the bottom of the glass, can be normal in a tight, energy-efficient home. The key is how often it happens, how long it lasts, and where it appears.

When condensation is usually normal

• Only appears on the inside of windows during very cold weather
• Shows up briefly after cooking, showering, or doing laundry
• Clears within an hour or two when you run fans or open a window slightly

When condensation is a warning sign

• Windows are wet or fogged most mornings, even in mild weather
• Water drips onto sills or soaks into trim and nearby walls
• You see mold or mildew on window frames, caulk, or drywall
• Condensation appears between the panes of double-pane windows

If you see moisture between the panes of a double-pane window, that often means the seal has failed and the insulating gas has escaped. In that case, no amount of indoor humidity control will fix condensation between the panes. The window or glass unit usually needs repair or replacement.

Step 1: Measure Your Indoor Humidity

Before you can control condensation, it helps to know your indoor humidity level. A small digital humidity gauge, often called a hygrometer, can give you a clear reading of the moisture in your air.

Ideal indoor humidity levels

• Winter: generally between 30% and 40% relative humidity
• Spring and fall: around 35% to 45%
• Summer: often 40% to 50%, depending on outdoor conditions

If your readings are consistently above these ranges, especially in winter, you are more likely to see condensation on windows. Use your readings as a guide while you try the fixes below and adjust until you find a level that keeps windows clear without making the air uncomfortably dry.

Step 2: Reduce Moisture at the Source

The less moisture you add to your indoor air, the less likely it is to end up on your windows. Start by tackling the biggest moisture sources in your home.

In the kitchen

• Use the range hood every time you cook, especially when boiling water or simmering soups.
• Make sure the range hood vents outdoors, not just back into the room.
• Cover pots with lids to reduce steam.
• Avoid leaving kettles or pans simmering for long periods.
• Run the dishwasher with the door closed until it fully cools and dries.

In bathrooms

• Run the exhaust fan during showers and for at least 15 to 20 minutes afterward.
• If you do not have a fan, open a window slightly during and after showers, if weather allows.
• Take shorter, slightly cooler showers to reduce steam.
• Keep the bathroom door closed while showering so moisture does not spread through the home.

Laundry and cleaning

• Vent clothes dryers to the outside, not indoors.
• Avoid drying clothes on racks inside if you already struggle with condensation.
• If you must air-dry clothes indoors, do it in a single room with a fan running and, if possible, a window slightly open.
• Do not leave buckets of water, wet mops, or damp rugs sitting for long periods.

Everyday habits that add moisture

• Limit the number of large houseplants in rooms that already feel damp.
• Keep lids on aquariums if you have them.
• Check for plumbing leaks under sinks, around toilets, and near the water heater.
• Fix any roof or wall leaks promptly to prevent ongoing moisture problems.

Step 3: Improve Airflow Around Your Windows

Even with moderate humidity, still air lets moisture settle on cool glass. Improving airflow keeps the surface warmer and helps dry any condensation that does form.

Simple airflow fixes

• Open blinds and curtains during the day to let warm room air circulate against the glass.
• Move furniture a few inches away from exterior walls and windows so air can move freely.
• Use ceiling fans on low settings to keep air moving without creating drafts.
• Run portable fans in problem rooms, aiming them so air flows across the window area.
• Keep interior doors open to allow air to circulate between rooms, unless you are containing moisture in a bathroom during showers.

Use fans effectively

Fans do not remove moisture on their own, but they help mix the air so humid pockets do not sit on cold surfaces. For the best results, combine fans with ventilation to the outdoors or with a system that actively removes moisture from the air.

Step 4: Ventilate Your Home to the Outdoors

Ventilation replaces moist indoor air with drier outdoor air. In many climates, especially during cold weather, outdoor air holds less moisture than indoor air, even if it feels chilly.

Use existing exhaust fans

• Run bathroom fans during and after showers for at least 15 to 20 minutes.
• Use the kitchen range hood every time you cook on the stove.
• Check that fans actually vent outside and that exterior vent covers are not blocked.

Use windows strategically

• Open windows on opposite sides of the home for 5 to 10 minutes to create a cross-breeze that quickly exchanges air.
• In winter, short, strong bursts of ventilation are usually more effective and comfortable than leaving a window cracked all day.
• Open a window slightly in rooms with persistent condensation, especially near problem windows, when outdoor conditions allow.

Whole-home ventilation options

If your home is very tight and you struggle with moisture even after using fans and windows, you may benefit from a balanced ventilation system that brings in fresh air and exhausts stale air in a controlled way. A local heating and cooling professional can evaluate whether that makes sense for your climate and home.

Step 5: Use Humidity Control Tools

In some homes or regions, especially in damp climates or basements, you may need extra help removing moisture from the air.

Dehumidifiers

A dehumidifier pulls moisture out of the air and collects it in a tank or drains it away. This can be especially helpful in:

• Basements and crawl spaces
• Rooms with little sunlight and poor airflow
• Homes with many occupants or high moisture activities

Place the unit in the dampest area, keep doors open so air can circulate, and set the target humidity around 40% to 45% in most seasons. Empty the tank regularly or connect a hose to a floor drain if the unit allows.

Adjusting humidifiers

If you use a whole-house or portable humidifier in winter, it may be set too high. While adding some moisture can make dry winter air more comfortable, too much leads directly to condensation on windows.

• Turn down the humidifier setting if you see regular window condensation.
• Use your hygrometer to keep humidity in the recommended range.
• Turn off portable humidifiers in rooms where windows stay wet.

Step 6: Make Your Windows and Frames Less Prone to Condensation

While humidity and airflow are the main levers, the windows themselves also matter. Colder glass attracts more condensation. Improving insulation and sealing air leaks can help keep the glass surface warmer.

Check and improve window seals

• Inspect caulk around the outside of window frames and repair any cracks or gaps.
• Check weatherstripping around sashes and replace worn or missing sections.
• Seal gaps where air leaks in, especially at the bottom and sides of windows.

Add temporary insulation

If replacement is not in the budget, you can make existing windows more comfortable:

• Use clear interior window film kits during the coldest months to create an insulating air layer.
• Add insulated curtains or cellular shades, but open them during the day to let warm air reach the glass.
• Use draft stoppers or weatherstripping along window sills where you feel cold air.

When to consider new windows

If your windows are very old, damaged, or have failed seals between panes, they may stay much colder than the room air, making condensation hard to control. Newer, well-insulated windows can reduce condensation, improve comfort, and lower heating and cooling costs. However, even with upgraded windows, you will still need to manage indoor humidity for the best results.

Special Situations: Condensation in Different Seasons

Winter condensation on interior glass

This is the most common situation. Cold outdoor temperatures cool the glass, and warm indoor air deposits moisture on the inside surface.

What helps most:

• Lowering indoor humidity to around 30% to 40%
• Using bathroom and kitchen exhaust fans consistently
• Improving airflow around windows and adding temporary insulation

Summer condensation on exterior glass

On hot, humid days, you may see moisture on the outside of cool windows, especially if your home is air conditioned. This is usually harmless and a sign that the glass is cooler than the outdoor air.

What helps most:

• Letting the sun or breeze dry the outside naturally
• Trimming plants that block airflow around windows
• Making sure exterior screens and storm windows are not trapping moisture

Condensation between window panes

Moisture between panes indicates a failed seal on an insulated glass unit. This is not caused by your indoor humidity level and usually cannot be fixed with ventilation or dehumidifiers.

What helps most:

• Contacting a window professional to discuss repair or replacement options
• Checking if the affected window is under any form of coverage

Protecting Your Home from Moisture Damage

While you work on controlling condensation, take steps to protect your home from existing moisture. Even small amounts of water can cause gradual damage if they sit on surfaces day after day.

Daily and weekly checks

• Wipe window sills and frames dry when you notice moisture.
• Look for peeling paint, soft wood, or discoloration near windows.
• Check for musty odors or visible mold on caulk, trim, or nearby walls.
• Clean any mold or mildew with an appropriate cleaner and let the area dry fully.

When to seek professional help

Consider contacting a professional if you notice:

• Persistent mold growth that returns quickly after cleaning
• Soft or rotting window frames or sills
• Condensation problems that continue even with lower humidity and good airflow
• Signs of water damage spreading into walls or floors

Putting It All Together: A Simple Action Plan

To stop condensation on windows, focus on steady, practical changes rather than one big fix. Here is a straightforward plan you can start this week:

1. Measure humidity with a small indoor gauge and aim for 30% to 40% in winter and around 40% to 50% in other seasons.
2. Use exhaust fans in bathrooms and the kitchen every time you create steam or moisture.
3. Reduce moisture sources by covering pots, shortening showers, venting dryers outdoors, and fixing leaks.
4. Improve airflow by opening blinds, moving furniture away from windows, and using fans on low settings.
5. Ventilate briefly but effectively by opening windows on opposite sides of your home for short periods.
6. Consider a dehumidifier in damp rooms or basements if humidity stays high.
7. Seal and insulate windows with fresh caulk, weatherstripping, and seasonal window film if needed.

With consistent attention to humidity and airflow, most homes can significantly reduce or eliminate annoying window condensation. The result is clearer glass, a more comfortable living space, and better protection for your home over the long term.

If you want to explore more ways to keep your indoor air comfortable and healthy, including tips on ventilation and temperature control, visit the main air and comfort hub for additional guides and resources.