No matter what anybody else tells you, if you are storing any items in a standard shipping container that is placed outside and exposed to the common European elements, you are susceptible to condensation occurring inside the container, which will more often than not collect on the ceiling.
How to prevent this
The very best method is using a powered dehumidifier…but that is only if you have power available. Without power, the next best option is a disposable dehumidifier. There are many types available, but of them all, a Dampstick is the best.
Why? Well it aggressively captures about 2.5 to 3 litres of moisture, and it is sealed preventing re-circulation in the container, it does not spill, they require no attention so that you can leave for months on end, and they are not expensive, see www.dampstick.com.
Many others will allow re-circulation and require emptying or reloading with crystals, or if a gel in a bag they can leak.
Grafo another product to control condensation, sprayed onto the ceiling is a material that absorbs moisture preventing condensation but does not remove moisture from the container, it has its uses, but it’s not a 100% moisture remover just a condensation preventer. Your supplier may be able to supply a container pre-Grafoed. see www.grafoproducts.co.uk.
Reducing the risk. This can be done by ceiling and wall insulation especially sides that get direct sunlight.
See Insulating a container cheaply.
What causes this? A standard shipping container is just a metal box which is quickly affected by ambient temperature changes. When the container is warm, so the atmosphere inside the container warms and can become humid. This humidity can materialise from a variety of sources for example…water trapped in the 27mm ply container floor, ( most common within Used Shipping Containers ), or water trapped in the items being stored, Like bedding, soft furnishings, dishwashers, washing machines, books, paper and more surprisingly “cardboard cartons” especially used cardboard boxes! All of these hold moisture to some degree. Also, air coming inside when you open the doors and you:- “your breath creates moisture”.
This humid atmosphere
When cooled during the evening, will form water droplets, usually on the ceiling, which can then, when the droplets are large enough drip onto your stored items. If this is not attended to, you will get over a period, a micro rain cycle, causing mould and water damage, which can wreak your stored items.
Some suppliers offer more vents and yes circulation of air is a good thing but not if it’s from outside and its damp air.
Also, no vents are fitted at ceiling level; they are all below the top rail which 90% of the time is a 50 or 60mm box section. So as humid air rises it is trapped in this space with nowhere to escape. Being the warmest place inside the container, it is not surprising that when the outside ambient air cools down, it’s the ceiling and that humid air that is always affected first.
Shipping lines that import clothing from the Far East always blank off all the vents and then control the air that is locked in, by using bag dehumidifiers that they throw onto the floor under the rails of clothing. 90% of your clothing is imported into the UK ! so they must know what they are doing.
Stay condensation free!
- Control what is going into your container.
- Control the ingress of damp air.
- Capture damp air in a Dampstick.