Why Condensation Is Worse in Cold Weather
By Ruth MacEachern
Product Manager
Feb 12, 2025
During the winter months, you are much more likely to wake up to see condensation on your windows in the morning. During cold weather, condensation can also form elsewhere in your home such as on walls and woodwork where it can cause bigger problems like mould that can negatively affect your health.
Understanding more about how and why condensation is worse during cold weather can help you to prevent it from becoming a problem in your home.
Where condensation comes from
Condensation is formed when air cools and can no longer hold as much water vapour. This usually happens when warm, moist air meets a cold surface.
The amount of water vapour that air can hold decreases as the temperature drops. At 20°C, a cubic meter of air can hold up to 17.3 grams of water vapour. However, when the temperature drops to 10°C, the same cubic meter of air can only hold about 9.4 grams of water vapour. This reduction in capacity explains why colder air is less able to retain moisture, leading to an increased likelihood of condensation.
The point at which condensation starts for form is known as the dew point. This is the temperature at which water vapour begins to condense into liquid water and is dependent on the humidity level.
In an average sized bedroom, if nighttime temperatures fall by 10°C, around 300ml of water will form as condensation on any cold surfaces.
Why condensation is more common on cold nights
As temperatures drop, we tend to heat our homes. Warm indoor air can hold more moisture, but at night when the heating is normally off and the house cools, the air temperature close to walls and windows will fall fastest to reach its dew point and condensation will start to form.
Condensation on walls is most commonly seen in houses with inadequate insulation. Such properties will experience much more significant temperature differences and lead to much colder surfaces.
Poor ventilation also contributes to increased condensation. During the winter, it is unusual to open windows as often, which means that the airflow is limited, and humidity will rise due to the air being trapped in the house for longer, meaning that the dew point will often be reached at a higher temperature than during a summer night when you might have open windows, or have allowed fresh air from outside to circulate during the day.
Why high levels of condensation are a problem
Condensation itself is not a major issue for householders. It is after all just water, however if it is not dealt with, it can lead to other problems for your home and family.
When condensation soaks into porous surfaces like walls, it will create damp patches which provide the perfect environment for mould to grow. Household moulds spread with microscopic spores which can be an allergen and cause respiratory and skin problems for people with weaker immune systems such as small children and the elderly.
In some cases, if damp patches from condensation are not dealt with, they can damage the plasterwork in your home which may require expensive repair.
Reducing condensation during the winter
Reducing the humidity level in your home is the most effective way to prevent condensation. Ensuring that you have extractor fans fitted in your kitchen, bathroom, and around other sources of steam such as washing machines and tumble dryers will help to remove moisture from the air before it has a chance to spread around your home. Modern extractor fans may incorporate a humidity sensor that means that they work automatically when the moisture levels in the air rise above a desirable level.
Whole house ventilation systems such as EnviroVent ATMOS can be fitted in most homes. Positive Input Ventilation systems draw air into your home at roof level and then distribute it around the house. This filtered air displaces the humid and stale air and reduces the likelihood of condensation forming.
Get help to reduce condensation in your home
Your local EnviroVent ventilation specialist can visit your property to carry out a free home survey that will identify the sources of moisture in the air and then provide you with advice about the best solution for your needs. Enter your postcode below to find an expert near you.
