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Shipping container condensation causes rust and other issues.

How to Stop Condensation in Shipping Containers

Shipping container condensation prevention and moisture control

As you can imagine, shipping containers are incredibly sturdy structures, designed to withstand long journeys by steamship lines, trains, and trucks so they can endure significant wear and tear and last longer than 35 years while still keeping their cargo safe.

Whether you are transporting or storing goods in a shipping container or live in a shipping container home, it’s important to be aware of the dangers of condensation and how to prevent it. 

Below we offer some advice on how to improve the airtight quality and prevent condensation in your shipping container. 

Why is shipping container condensation a problem?

No matter how you use your shipping container(s), moisture can lead to structural damage to the container, such as rust and corrosion. This can weaken its lifespan and make the container more vulnerable to the elements and daily wear and tear. 

If you are using a shipping container for transportation or storage purposes, condensation problems can cause damage to the cargo or goods inside the container. For nearly any item, condensation can lead to rust, mold, and mildew. Meanwhile, moisture-sensitive items such as electronics, paper products, and textiles can be ruined completely by this exposure to moisture.

Lastly, if you live in a shipping container home, it is particularly important to be aware of the potential health hazards. Moisture in shipping containers can create a breeding ground for mold and bacteria, which can pose health hazards to anyone who comes into contact with the container or its contents.

What causes condensation in shipping containers?

Condensation in shipping containers is caused by a combination of temperature, humidity, and air circulation.

Condensation often occurs when the inside content of a container (goods or the air itself) is warm and/or humid, and that container is placed in colder conditions. Think about your car in the winter: when your warm, humid breath hits the cold glass of the windshield, it begins to “fog up” with condensation. This is essentially what happens in a container.

The walls of shipping containers are built from steel to be strong and durable, but this material typically takes on the temperature of its surroundings quickly, as well. This means that even if the air and cargo inside your container are at a “normal” temperature, if moved suddenly to a colder location, the air can no longer contain its moisture (dew point) and condensation begins to form on the shipping container walls. 

Condensation can also be caused by poor air circulation. If the air inside the container is stagnant, the moisture in the air will not be able to evaporate, and it will instead accumulate on the surfaces of the container interior.

Are shipping containers water/wind & airtight?

The majority of shipping containers are not entirely watertight or airtight. They have small vents and the doors have rubber seals to stop water from entering, but not air. This keeps the circulation at its best to protect your goods. 

Typically, containers are manufactured with 8 x 2 x 1” vents that are covered with mesh to prevent bugs and insects from getting in and out of the container. You typically will get 2 vents on a 20ft container and 4 vents on a 40ft container. These vents must be small to ensure that no water enters the container during overseas transport, but condensation can still occur.

Reefer (refrigerated) containers are insulated units that are void of openings as circulation inside the box will disrupt the cooling or heating mechanism.

The condition of a container can also affect how water & wind tight the container is, with damage to older used containers compromising the container’s integrity. 

Container Sales Group inspects all of our used shipping containers to ensure that the vents are intact and that our containers are water & wind-tight for storage. 

4 ways to keep moisture & condensation out of your shipping container

While it’s impossible to completely prevent moisture buildup, there are ways to control condensation in your shipping container.  

  1. Ventilation: The simplest and most cost-effective way to control moisture & condensation is ventilation. This will ensure air is circulating through your container and help reduce or prevent condensation. Ventilation also helps equalize the temperature of the container compared to the outside environment. Be sure no cargo is completely obstructing the shipping container vents and stopping this critical airflow. 
  2. Insulation: As we mentioned, the metal used to build shipping containers is extremely sensitive to taking on temperature changes, which can contribute to condensation. Insulating your shipping container will keep the temperature warmer than the dew point, therefore preventing condensation from forming.  You’ll need proper material depending on the climate, so reach out to a home improvement professional. Some of the materials include supaloft, spray foam, and therma fleece. 
  3. Dehumidifier: Adding a dehumidifier to your shipping container can also help prevent condensation. These units take water out of the air and could be a good option to protect your goods if you can run electricity to your storage container. They’re affordable and easy to set up. 
  4. Desiccants: Desiccants are a low-cost option that absorbs excess moisture from the air, thus reducing the condensation inside of the shipping container. They can be on your wall, in bags on the floor, or as paint on the roof interior and walls of your shipping container. You can even purchase a spray applicator to apply the desiccants to your shipping container. 

Here is a link to a product that some of our customers use to keep moisture out of their containers.

Work with the best in the shipping container business.

Container Sales Group buys containers directly from the steamship lines to offer our customers the highest quality containers at the most competitive prices. We’re a women-owned business, established in 1998, and have locations throughout the US.

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