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Window condensation - where the water vapour comes from

Window condensation, a perennial problem for homeowners, moves through the seasons, leaving its mark on both the beauty and comfort of our houses. In this investigation, we will uncover the secrets of window condensation, diving into the many components that contribute to this phenomena. Join us on a trip as we explore the nuances of humidity, the influence of insulation, and the unsuspected culprits that might be quietly creating havoc in your house.


What is condensation?

The transformation of a gas or vapour into a liquid is called condensation. When a gas or vapour's temperature falls below its "dew point," something happens. This is what causes morning dew on the grass: during cold nights, the earth releases heat skywards, causing the ground's temperature to drop below that of the air, allowing water vapour to condense on it as dew.

When it's chilly outside, you can see your breath because the water vapour in your exhaled air is hotter than the air you inhale, causing it to condense and create a mist.


Condensation happens due to three major factors: humidity, temperature, and ventilation.

  • Humidity - Humidity is a major source of moisture in the house. Everyday activities generate a lot of moisture, which sits in the air. Taking a warm shower and boiling water are both wonderful examples.

  • Temperature - Temperature is another factor. When interior and outdoor temperatures differ, it provides an excellent setting for condensation on windows.

  • Ventilation - The last aspect is ventilation. Allowing air to flow around helps to keep humidity levels low. Proper ventilation allows you to remove damp air and replace it with dry air.

Condensation occurs on windows because their surface is cooler than the surrounding air. Condensation occurs when heated air comes into contact with cold glass. It is especially frequent in the winter when windows remain colder owing to the chilly temperatures outside and warm air within.

With that stated, condensation on windows may occur at any time of the year. In the summer, you may chill your house to create a same condition as in the winter, but with hot air outside and cold air inside.

Temperature disparities in windows occur regardless of how costly or well-made they are, due to their materials and design.

Humidity may readily spread throughout your house, no matter where it originates. For example, if you take a hot, steamy shower, the humid air may pass through the porous materials in the walls and doors to neighbouring rooms, causing condensation on the windows.

Condensation is particularly common in recently constructed houses due to their energy efficiency. A well-built house prevents air leakage from inside to outside and vice versa, which is beneficial to fuel and electric expenses but offers the ideal setting for window condensation.

The Intricacies of Humidity:

Humidity, which is sometimes overlooked, plays an important role in the window condensation drama. It extends beyond exterior weather conditions, since our everyday activities have a significant impact on interior humidity levels. The act of cooking in the kitchen, taking a hot shower, or just breathing emits water vapour into the air. The aggregation of these apparently benign activities may raise interior humidity, setting the scene for unwanted condensation to form on your windows.

Ventilation, the often-overlooked hero, emerges as a critical component in the fight against window condensation. A well-ventilated house functions as a conduit, allowing excess moisture to leave. In places prone to moisture accumulation, such as the kitchen and bathroom, installing exhaust fans or just opening windows may make a huge impact. Avoid allowing your house become a sealed chamber; instead, bring fresh air in to maintain a healthy balance and prevent condensation.

The Role of Insulation:

Windows, seen as the protectors of interior comfort, might accidentally contribute to condensation if not properly insulated. Single-paned windows or older versions are more prone to temperature swings, providing a perfect setting for condensation to thrive. Weatherproofing, whether achieved via the use of weatherstripping or the installation of double-glazed windows, serves as a protective barrier against temperature differentials that cause moisture.

Unexpected Moisture Contributors:

Indoor Plants:

It is crucial to recognise the wetness that indoor vegetation brings in, despite the fact that it provides a literal breath of fresh air with its presence. When plants go through a process called transpiration, they emit water vapour into the atmosphere, which contributes to the overall humidity levels. Think about strategically relocating or grouping them in order to lessen the effect they have.

Appliances at Play:

There is a cost associated with modern conveniences that is wetness. There is a major contribution made by home appliances such as dishwashers and laundry dryers to the production of moisture. It is necessary to ensure that these appliances have enough ventilation and that they undergo routine maintenance in order to prevent the accumulation of surplus water vapour.

Furniture Placement:

It is surprising to learn that the placement of furniture might have an effect on condensation. The placement of furniture against external walls may result in the formation of pockets of stagnant air, which in turn can lead to temperature variations and, as a cause, condensation. It is important to keep a watchful eye on the arrangement of your furniture in order to promote good ventilation and prevent condensation.

Taking Action:

Dehumidifiers as Allies:

In order to effectively combat window condensation, it is necessary to take preventative measures as well as proactive ones. By removing excess moisture from the air and ensuring that the humidity level remains at an acceptable level, dehumidifiers have emerged as reliable companions. When dehumidifiers are strategically placed in locations that are prone to condensation, it is possible to drastically minimise concerns that are connected to moisture.

Smart Window Upgrades:

Making an investment in windows that are energy-efficient and have coatings that have low emissivity is a strategic step that may be taken against condensation. Not only do these windows provide several advantages in terms of insulation, but they also control the temperatures inside, so reducing the likelihood of condensation happening.


Window condensation may seem like an enigma, but armed with knowledge, you can turn the tide. Addressing the intricacies of humidity, fortifying your home with proper insulation, and identifying unexpected contributors can transform your living space into a condensation-resistant haven. The battle against window condensation is not merely about maintaining clear glass; it's about cultivating a comfortable, healthy, and moisture-balanced home. Armed with strategic measures and a comprehensive understanding, homeowners can reclaim their living spaces from the clutches of window condensation.

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