Does Condensation Occur in Storage Containers?
Does Condensation Occur in Storage Containers? Yes. Condensation can occur inside an uninsulated steel storage container when humid air comes into contact with steel walls or a roof that have become cold enough for moisture in the air to condense.
This is one of the main reasons why all Boxed Up storage containers are insulated.
What Causes Condensation in a Storage Container?
The cold bottle shown in the picture is a simple example of how condensation forms.
The bottle is not leaking. The water droplets come from moisture already present in the surrounding air. When warm, humid air comes into contact with the cold surface of the bottle, the air next to the glass cools. If it cools below its dew point, some of the water vapour changes into liquid water and forms droplets on the surface.
The same thing can happen inside a steel storage container.
During the day, the container and its contents may warm up. When the outside temperature falls, particularly overnight, the exposed steel walls and roof of an uninsulated container can cool rapidly.
If the internal surface becomes cold enough, water vapour in the air can condense on the steel. Water may then form on the walls and roof, run down the sides or drip onto stored belongings. This is sometimes called container rain.
Why Does Insulation Reduce Condensation?
Condensation depends on two things: there must be sufficient moisture in the air and there must be a surface cold enough for that moisture to condense.
A standard shipping container has a thin steel skin separating the inside from the outside weather. Steel conducts heat well, so an uninsulated internal surface can respond quickly to changes in the outside temperature.
Insulation creates a thermal barrier between the stored contents and the external steel. This helps keep the temperature of the internal surface more stable and reduces the likelihood of it becoming cold enough for condensation to form.
Insulation does not remove moisture from the air and cannot guarantee that condensation will never occur. It does, however, address one of the main reasons condensation occurs inside steel containers.
Where Does the Moisture Come From?
A container does not need to have a leak for moisture to be present. Water vapour is naturally present in the air, and additional moisture can be brought into the container within the items being stored.
Common sources include:
- Furniture, fabrics and clothing stored while damp
- Washing machines, refrigerators and other appliances containing residual water
- Wet garden, camping or sports equipment
- Damp cardboard, timber and other absorbent materials
- Humid outside air entering when the doors are opened
- Belongings being loaded during wet weather
Keep Moisture Out of Your Storage Container
The simplest way to reduce the amount of moisture inside a container is to make sure belongings are dry before they go into storage.
- If possible, avoid loading during heavy rain
- Make sure furniture and soft furnishings are dry
- Dry clothes, bedding and mattresses thoroughly
- Empty and dry washing machines, refrigerators and freezers
- Remove wet mud and grass from garden equipment
- Dry tents, inflatable boats and sports equipment before storing them
If belongings go into storage damp, the water they contain can gradually evaporate into the air inside the container.
What If Your Belongings Are Already Damp?
Sometimes it is not practical to ensure that everything is completely dry before it goes into storage. Furniture, fabrics and other absorbent materials can contain moisture even when they do not feel particularly wet.
Boxed Up Storage will loan customers a dehumidifier free of charge for up to two weeks to help remove excess moisture from belongings when they are first put into storage.
A dehumidifier removes water from the air as moisture gradually leaves the stored items. The collected water can then be emptied from the machine rather than remaining inside the storage environment.
Electricity is also available as an option if a dehumidifier is required for longer.
There are also passive moisture absorbers and container desiccants available. These work differently and have a much smaller moisture-removal capacity than an electric dehumidifier.
For more information, see Dehumidifiers or Moisture Absorbers for Storage?
Does Ventilation Stop Container Condensation?
Ventilation can help by allowing moist air inside a container to escape, but it is not a complete solution.
Its effectiveness depends on the temperature and humidity outside the container. If the outside air is already humid, introducing more outside air will not necessarily make the inside of the container drier.
The small vents fitted to standard shipping containers provide only limited air exchange. They should not be relied upon to remove significant amounts of moisture from damp furniture, equipment or other stored belongings.
What About Mould and Musty Smells?
Persistent moisture can increase the risk of mould and musty smells, but this is a separate subject from condensation itself.
For information about why mould develops, which stored items are most vulnerable and how to reduce the risk, see our guide to Preventing Mould & Storage Odours.
Why Boxed Up Insulates Its Storage Containers
Many container storage sites use standard uninsulated shipping containers. At Boxed Up, our containers are insulated because controlling the temperature of the internal surfaces helps reduce the conditions in which condensation forms.
Insulation also helps reduce the temperature extremes that can occur when a steel container is exposed to direct summer sunshine or cold winter weather.
For more information about heat and storage containers, see Do Storage Containers Get Too Hot?
Keeping belongings dry before storage, reducing unnecessary moisture and using an insulated container all help reduce the risk of condensation. Where additional moisture control is required, a dehumidifier provides a further level of protection.