Why Are Container Houses Damp

The heavy dampness in container houses is mainly related to factors such as the characteristics of metal materials, temperature variations, ventilation design, cargo packaging, and container body damage. Here are the specific reasons and analyses:

'Container Rain' Caused by Metal Materials and Temperature Variations

Most containers are made of metal materials with high thermal conductivity, and the internal temperature changes rapidly with the external environment. In areas with maritime transportation or large temperature differences between day and night, when the temperature rises during the day, seawater evaporates, increasing the air humidity. At night, when the temperature drops sharply, the water vapor in the air condenses into water droplets on the inner walls of the container, forming 'container rain'. This repeated temperature variation causes continuous accumulation of water vapor, leading to increased dampness inside the container.

Ventilation Design Flaws and Poor Air Circulation

If the ventilation design of the container house is unreasonable, such as long-term closure of doors and windows or obstruction of ventilation openings, it will hinder air circulation. The water vapor generated by daily activities (such as cooking and bathing) cannot be discharged in a timely manner, further exacerbating the accumulation of dampness. In addition, although the airtightness of the container can prevent rainwater from entering, it also restricts the natural diffusion of moisture.

Cargo Packaging and Residual Moisture in the Container Body

Cargo with high water content (such as textiles and agricultural products) or packaging materials with strong moisture absorption (such as cardboard boxes and wooden pallets) can indirectly release water vapor. If the container is not thoroughly dried before loading (such as not being air-dried after cleaning) or if damp wooden dunnage is used, the residual moisture inside the container will evaporate with temperature changes and re-condense into dampness.

Container Body Damage and Infiltration of External Moisture

During long-term use, containers may develop cracks, holes, or aging of sealing strips, allowing external rainwater or moisture to directly seep in. Especially in humid climates or coastal areas, where the air humidity often exceeds 70%, moisture infiltrates through gaps and is difficult to discharge, further worsening the dampness problem.

Prevention and Improvement Measures

• Moisture-proof packaging: Use waterproof plastic bags, aluminum foil films, or vacuum packaging to seal the cargo and isolate external moisture.
• Application of desiccants: Hang calcium chloride or mineral desiccant rods inside the container to continuously absorb moisture from the air.
• Ventilation optimization: Open windows regularly for ventilation and install exhaust fans to enhance air circulation and prevent the accumulation of water vapor.
• Container body maintenance: Before loading, check whether the container is dry and clean, repair damaged parts, and ensure that the sealing strips are intact.
• Material selection: Use insulation materials such as EPS boards and rock wool boards for the exterior walls to reduce the formation of condensed water caused by temperature variations.