Damp in 20ft and 40ft Shipping Containers

Damp (also known as ‘container sweat’ or ‘condensation’) is a natural process that can occur in shipping containers of all sizes, or any metal box left out in the elements, and is not just limited to the larger 20ft and 40ft units. Mainly, condensation forms on the roof or ceiling of the container. Condensation can be caused by storing damp or wet goods inside the the container or by climactic conditions such as a change in temperature and higher levels of humidity.

There are a number of solutions and products that can be used to minimise the damage to goods caused by condensation or damp inside the container, including products such as Grafo-Therm, SeaDry Hooks, Absorpoles and insulation kits.

SeaDry Hooks

Interior of a shipping container. Lining the walls are long strips of yellow packets.SeaDry Hooks, also known as SeaDry Sticks, provide a temporary but effective solution to prevent the build-up of condensation in your container. These sticks can absorb up to 1.2 litres of water per stick and should last for up to 12-weeks depending on conditions, such as the climate in your area, the weather at the time and the goods being stored. The sticks are simply hung from the cargo hooks within the shipping container and fit snugly within the corrugations.

Although they work similarly to the packets of silica gel desiccant you might get with a new pair of shoes, they are much more effective than Silica Gel or Desiccated clay. They contain a mixture of salt and modified starch, are non-toxic and can be disposed of in normal waste.

The sticks are manufactured in Germany under ISO 9001:2008 certified manufacturing conditions. The manufacturer advises using 10 SeaDry hooks in a 20ft container and about double the amount in a 40ft unit.

Absorpolesthe interior of a corrugated shipping container - thin rectangular metal rods line the side of the container, snugly nestled in the indents of the corrugations

Absorpoles, like the SeaDry Hooks, are environmentally friendly and contain no hazardous or toxic materials. Also known simply as Shipping Container Moisture Traps, they are made from recycled plastics and can themselves be recycled after use. They have a wide temperature range working from -20 degrees C to +80 degrees C and hold some 2 litres of captured moisture. In a 20ft shipping container, the manufacturer advises that 4 x Absorpoles are used and 8 in a 40ft container.

They last just as long as the SeaDry Hooks, between 6-12 weeks depending on the amount of moisture in the air and can be drained into sewage and disposed of in your regular waste. They are made with a grey 100% recycled plastic casing that matches they typical lighter grey colour of a shipping container interior, making them a handsome, environmentally friendly choice of desiccant for your shipping or storage container.

Insulation Kits

an empty shipping container lined in insulated material.Insulation kits, also known as lining kits, are an excellent way to prevent condensation build up and moisture damage in your shipping container. They typically come in made-to-measure rolls for a range of container and flat pack sizes and can easily be cut down to fit the tricky in-between sizes. They can be easily installed or taken down at home by yourself and a friend in about half an hour and sticks to your container with a thermal bonding tape which, once your container warms it in the sun, should last a good few years.

We recommend this option as a good alternative to the longer-lasting permanent insulation options such as Grafo-Therm or ply lining and insulation, for when you already own a container and might not want to pay a workman to come over and modify your container or take it away for modifications. They also come in cheaper than a polystyrene alternative, and they look far prettier, too.

Grafo-Therm Container Condensation Treatment

Grafo-Therm is a long term solution for preventing damp and mould in your container, typically lasting around 6-7 years. It’s a spongy substance that we can spray onto the ceiling of your shipping container interior – it comes out in thin white/light grey layer which will match most shipping container interiors and can be sprayed on at one of our depots before your container is sent out, or in some circumstances we can send a “man with a van” out to spray it at your site.

Not only does it trap and absorb any moisture coming through your container’s ceiling, it also incorporates a fungicide into its mixture, that prevents fungal growth and mould from forming.

While Grafo-Therm is only applied to the ceiling and doesn’t prevent moisture from forming on the sides of the container, simply ensuring that any more delicate items such as clothing, cardboard or wood are being stored away from and not touching the sides of the container should prevent any moisture from seeping in and causing mould. It is also not recommended to have your goods touching the ceiling when Grafo-Therm is applied, as it works best when there is air flowing around/across it.

Lining and Insulation

The inside of a shipping container. The walls and ceiling are both lined with plywood.As it says on the tin, container lining and insulation consists of two major components – an insulated material, typically rockwool or a similar material, overlayed with a lining, typically made of plywood or melamine, which can be wiped clean.

It is usually installed on all three sides of the container, the ceiling and on the backs of the cargo doors and is entirely customisable – from the panelling used to the type and thickness of insulation inside. A frame is built inside the container out of of 2×2 or 4×4 wooden batons and fixed to the inside wall, then the cavity spaces in the frame are filled with your choice of insulation, such as rockwool, and panelled over the top with ply wood, melamine or another material.

This is very much a premium option and is most popular in containers that are to be made into units such as office spaces or kiosks, but it still works perfectly for just storing goods, and when built well will not only reduce the rate at which heat will escape your container, but will also prevent condensation from forming, therefore removing the risk of mould.

As a premium choice, this is one of the more expensive options available. However, it is also the most effective option and one we highly recommend, especially for a container modified into a unit you will be spending a lot of time in.

Budgetshippingcontainers.co.uk offer the UK’s largest online range of shipping containers for sale with a nationwide network of storage and conversion yards and crane equipped delivery vehicles.

If you need a shipping container feel free to browse our online range of shipping containers for sale. You can also call us on freephone 0808 1234 215 any time 9am – 5pm weekdays and our team will be happy to discuss your requirements. Alternatively, you can use our online shipping container quote form or request a telephone callback. In both cases we aim to get back to you within 1-2 working hours (may take longer for more detailed quotes).

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