Shipping Container Condensation – How to Help Protect Yourself

So you’re just about to order a shipping container for storage and you’re wondering if you need to take any added steps to protect your belongings from condensation damage.

What causes shipping container condensation?

Before we start to consider solutions for shipping container condensation prevention it’s useful to understand what causes condensation in the first place.

Simply put condensation is a phenomena caused by a combination of internal and external temperature differentials, together with high humidity levels reaching what is known as ‘Dew Point’ – which leads to condensation.

When condensation within freight containers does occur it’s normally most prevalent on the roof and top six inches of the side-walls.

The main keys to condensation control are ventilation and/or de-humification.

Container storage – my personal experience.

Almost 2 years ago my apartment in London became a little overcrowded with things I had collected along the way.

As someone working in the shipping container business I naturally turned to the idea of using a container for storage to solve the problem.

Storage boxes ready to be loaded into a shipping container

My excess belongings included quite a few boxes of clothes as well as many old books which I was a little reluctant to get rid of – but they had to go.

With that in mind I went ahead and picked out a new 20 foot storage container just in from the factory.

How low cost vents worked well for me in preventing condensation.

When you see a typical storage container fitted with vents you will usually notice the vents are located on each side of the unit.

The problem with this is that when containers are placed next to each other air flow can be restricted.

The great thing about Adaptainer’s new build units is that they are specially manufactured with ventilation at each end (rather than the sides).

storage container vents internal

Placement of vents on doors of Adaptainer units allow airflow even when containers are adjacent to each other

Storage container anti condensation vents

External view of container door vents

This minor but important alteration means that if you’re placing containers adjacent to each other the vents are not obscured.

As a result you’re able to benefit from increased air flow through end to end ventilation.

With this reassuring knowledge in mind I finished loading the container up,  the doors were shut and I happily went back to my newly spring cleaned home.

The end result.

This all happened around two years ago and I’m glad to report that only last week I re-entered the container to see that all my belongings were in the same condition as I had left them – despite not having taken any additional anti condensation measures.

What if you need more vents after the containers have been purchased?

If you find yourself needing further airflow in the container after taking delivery of the box you can buy extra vents very inexpensively for DIY installation.

These are normally separate plastic components with labyrinth baffles and a gasket to prevent ingress of water when riveted to (customer installed) holes on the container side/end wall.

Other anti-condensation solutions.

In my experience the small ventilation points at the end of the container proved to be adequate, but would container vents alone be adequate for you?

Since every container storage case is different there isn’t a straight yes or no answer that I can give to this question unfortunately.

But let’s review some other anti-condensation options available and it’s up to you to make up your own mind about what might work best in your case.

De-humidifiers.

Since we’ve already considered vents next up is de-humidification equipment – which is available to buy from a variety of suppliers.

Water extracted by the humidifier should be dumped through pipework supplied to the exterior of the container, this is to prevent re-circulation.

The number of times an access door is opened, thereby allowing the entry of humid air (particularly during winter months) is a crucial contributing factor.

Although, this type of equipment may have automatic on/off features utilising sensors to detect moisture.

Moisture absorb poles.

Alternatives to de-humidifiers are the likes of the relatively inexpensive moisture absorbing poles which are non-mechanical.

Moisture absorb poles are profiled to the shape of a container’s typical corrugated side-wall and the pole can be fastened by hanging it to one of the container’s upper lashing hoops.

The advantage of this convenient placement is that the interior cubic loading capacity of the container is not reduced.

How do moisture absorb poles work?

Contained within the pole are salts which absorb moisture when a silver protection foil is peeled off, thereafter permanently dumping the collected moisture in the form of a gel into it’s built in “tank” for evacuation and replacement when the salts are depleted.

Each pole typically lasts for a few months at a time but lifetime is dependent upon humidity levels combined with the number of times the container doors are opened.

The advantage of this particular product over the likes of silica gel desiccants (which absorb but also release moisture) is that the process is one-way only.

Grafotherm.

Another solution to help fight against condensation is Grafotherm.

This anti condensation coating is typically applied to the container roof and top six inches of the side-walls using spray applicators.

Shipping container condensation prevention - Grafotherm

Roof of a shipping container coated with Grafotherm

 

The coating once applied acts as a partial insulation which can also retain some moisture within it’s structure.

Since it’s introduction Grafotherm has been recognised as being a worthwhile solution and is used by some mini-storage container compounds throughout the UK for example.

Container lining.

Lined shipping / storage container

Shipping container with lining

The addition of thermal lining inside of a container is our final option to help reduce condensation.

Some types of lining can be very economical, resembling gigantic sheets of bubble wrap with foil coated on one side and installed using double sided industrial adhesive tape.

Whilst this can be a good way of reducing condensation do bear in mind that lining will not remove the risk entirely as condensation is an airborne element and not exclusively controlled by temperature differentials alone.

This slight flaw is frequently proven in refrigerated container bodies and even domestic fridges which often exhibit ice crystals inside.

Shipping container anti-condensation summary.

As few or as many of these suggestions can be employed in combination to calm any fears you may have of potential condensation damage to goods stored.

Do bear in mind that factors causing the phenomenon are variable depending on elements such as location, season and usage.

As a result there isn’t a ‘one size fits all’ anti condensation procedure that we can recommend.

The possible solutions outlined above are to be chosen at your discretion but have all been proven to satisfy specific requirements by various customers over the years.

In summary many of our customers have used shipping containers with vents fitted for storage purposes and not noted any condensation problems whatsoever, I am one of them.

However to present a fair and balanced picture others have.

I hope these tips have helped you to understand some of the anti condensation solutions available to you, often at extremely low cost.

 

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