How to Prevent Condensation in Shipping Containers

Condensation can be a challenge to manage in any space, but shipping containers and other non-ventilated buildings can be a magnet for condensation. If left unchecked, condensation can even cause mould, damaging furnishings, flooring and more in shipping container conversions.

In this guide, we cover how to stop condensation in a shipping container with a few key tips to help you keep your container clean and dry.

What Causes Condensation in Shipping Containers?

When utilised for their original purpose, shipping containers are designed to be watertight, and in rare cases, airtight too. These features enable containers to remain weatherproof, protecting their contents against the ingress of rain or sea spray. This means that, unlike traditional extensions or garden rooms, they do not have the benefit of strong ventilation to prevent condensation.

This lack of ventilation is further worsened by ‘container sweat’, where warmer, moist air hits the cold steel of the container and creates a wet surface, typically on the roof. A container that is utilised as a living or gym space, for example, will have a great deal more moisture in it than in a container that is utilised as a simple and effective solution for extra storage space. In combination, these two factors can lead to a problem that, if unmanaged, can cause the growth of mould on items in your shipping container.

Why is Condensation in Shipping Containers a Problem?

Condensation in shipping containers is problematic in the same way it would be for any structure. When shipping containers are in active use, condensation can cause spoilage or damage to items being shipped. This is why many shipping containers have a venting system that helps with condensation for non-human occupation.

For retired containers that are used for secondary purposes, such as gyms, offices or living spaces, condensation can be directly harmful to your belongings. For example, soft furnishings or wooden items may become damp, which can cause mould. Condensation can also be dangerous, making the floor or equipment wet and slippery, and potentially causing injury. Electronics can also be at risk of breakage due to condensation.

Insulation Options for your Shipping Container

Plywood Lining

A plywood lining offers protection against condensation by physically creating a space between the outside of your container walls and the inner space that you use. Plywood is used to line the container in sheets, with a cavity that can be filled with insulation materials. By preventing the significant difference in temperature, a plywood lining can reduce the amount of condensation that occurs.

Plywood is cost-effective and can even be attempted at home as a DIY project. However, the roof in particular needs to be installed correctly, and failure to do so can render your efforts ineffective. Prices vary considerably with this method, depending on your choice of materials.

GrafoTherm Paint

GrafoTherm is often considered the industry standard method to prevent and treat issues with condensation. This coating absorbs moisture directly, helping to reduce the overall water content within the shipping container by effectively trapping and holding any condensation. GrafoTherm is relatively cheap as a solution and is long-lasting.

The main downsides to this condensation prevention method are how difficult it is to apply and how long it takes to set, often far longer than the 10–12 hours suggested. GrafoTherm is solely applied to the roof, which makes it even messier for DIY purposes and best left in the hands of professionals where possible.

Insulation Kits

An insulation kit is a pre-built solution for insulating your shipping container at home. Typically, these kits include both an insulation material like polystyrene, in addition to thick sheets of laminated foil, helping to prevent condensation. One of the key benefits is that insulation kits are pre-cut to size, enabling you to install them quickly and easily.

Insulation kits require little skill to install and often include a sticky back to apply directly to the wall and roof. However, to ensure insulation kits do not fail, the interior walls need to be thoroughly cleaned and free of any pre-existing condensation, otherwise the sticky parts of the panels may come unstuck.

Additional Vents

Installing additional vents can be a viable way to prevent condensation in shipping containers, similar to how you’d ventilate rooms in your home to prevent condensation on windows. There are two types of vents you can choose for shipping containers: standard container vents or louvre vents.

While the smaller vents are less obtrusive, they are also not as effective in preventing condensation. A louvre vent is significantly larger but provides much better airflow, though small insects may be able to gain access through this type of vent. Additional mesh can help to prevent this problem, though it’s worth noting that you’ll likely want a professional to install your vent rather than DIY-ing it.

Melamine Lining

Melamine offers a wipe-clean alternative to plywood with many of the same benefits. The hygienic nature of melamine makes it well-suited for catering and food preparation, in addition to its use in toilet blocks and changing rooms. Like plywood, melamine is layered with insulation to prevent condensation.

While melamine has a clean look, its wipe-down surfaces can also feel quite clinical for personal use. This material typically comes in stark white and requires additional steps and preparation if you would like to paint it, as it is a smooth and shiny surface. This material is a good fit for commercial applications over residential ones.

Dehumidifying Units

A dehumidifying unit offers a cost-effective method for the removal of moisture from the air. These units are available in a range of sizes from retailers, though in most cases, you will want a plug-in electric dehumidifier for best results instead of the smaller, disposable dehumidifiers with silica gel beads.

The two biggest problems with dehumidifying units are powering them and emptying them. You will need a power outlet to plug in your dehumidifier and ideally leave it running throughout the night, so the container is dry during the day. Dehumidifiers also usually need to be manually emptied, though some have attachable hoses for direct draining.

Absorpoles

Absorpoles are similar to disposable dehumidifiers but on a larger scale, holding up to 2 litres of water. These containers are filled with calcium chloride, a highly absorbent desiccant, that absorbs moisture in the air. The number of poles you need will depend on the size of your shipping container, with a rough estimate of one pole per ten feet of container.

As a disposable resource, these poles require replacement when they are full, which means that they will be a continual cost to keep condensation low. They are highly cost-effective and easy to use, making them a simple and easy choice for keeping your container condensation-free.

Refrigerated Containers

A non-operational refrigerated container has the benefit of a high standard of insulation built directly into the walls and roof, requiring no additional work to achieve a condensation-free space. These non-operational units are rare, as they require the container to have received a specific type of damage that renders the engine non-repairable.

If you go for this option, it’s vital that you choose a container that is in good condition. Any hole in the exterior will allow water to ingress into the cavity, waterlogging the structure inside. It’s also very difficult to modify the insides of these containers, though these units are already food-grade, making them suitable for food or catering use.

Shipping Containers at KH Containers

Taking the necessary steps to protect your shipping container from condensation helps to protect your belongings while improving the usability of the unit. KH Containers has more than 10 years of experience in container conversions. We offer a wide range of units in different sizes, including 10ft, 20ft and 40ft containers for many different applications.

We can work with you to create a bespoke shipping container that suits your goals, with full protection against condensation. Call us on 0333 577 3191 or get in contact directly to discuss your shipping container requirements and get a quote for a new or used shipping container.