Condensation inside shipping containers — known as “container rain” — is the single biggest problem faced by container owners across Ireland and Northern Ireland. When warm moist air inside the container meets the cold steel walls and ceiling, water forms and drips onto everything below. This guide explains why it happens and how spray foam insulation eliminates it permanently.
Why Do Shipping Containers Get Condensation?
Shipping containers are made from single-skin corrugated steel with zero insulation. Steel conducts heat rapidly, so when external temperatures drop at night or in winter, the internal steel surface becomes a cold condensation magnet. Any moisture in the air inside the container condenses on the cold steel and drips down — soaking stored goods, causing corrosion, ruining electronics and creating mould.
This happens in every uninsulated steel container in Ireland, regardless of whether it is used for storage, as an office, workshop or any other purpose. The Irish climate — mild, wet and humid, with frequent temperature swings between day and night — makes it particularly severe.
How Spray Foam Stops Container Condensation
Closed-cell spray foam (Nexseal LE) eliminates container condensation by solving both causes simultaneously:
- Thermal barrier — the foam raises the internal surface temperature above the dew point, so moisture in the air never reaches a cold enough surface to condense
- Vapour barrier — the closed-cell structure prevents moisture migrating through the insulation to reach the cold steel behind
- Seamless coverage — spray foam bonds directly to the corrugated steel walls and ceiling with zero gaps, unlike rigid board which leaves air spaces at every corrugation
A 25mm application of Nexseal LE is typically sufficient for anti-condensation protection in storage containers. For container conversions (offices, workshops, habitable spaces), 50-80mm provides full thermal insulation, with the final thickness set by the TGD L 2022 requirements that apply to the conversion.
Other Methods vs Spray Foam
| Method | Stops Condensation? | Notes |
|---|---|---|
| Desiccant bags | Temporary only | Need constant replacement, do not solve the root cause |
| Ventilation | Partially | Lets in more humid air in the damp Irish climate, can make it worse |
| Anti-condensation paint | Partially | Absorbs some moisture but saturates quickly |
| PIR rigid board | Partially | Gaps behind corrugations allow cold bridges and condensation paths |
| Spray foam (Nexseal LE) | Yes — permanently | Bonds to corrugated profile, integral vapour barrier, no gaps |
How Much Does It Cost?
Anti-condensation spray foam for 20ft and 40ft shipping containers is priced by specification as a fixed quote. Full conversion insulation (50-80mm for habitable use) costs more. Duratite provides free surveys and fixed-price quotations — email info@duratite.ie.
Read our complete guide to shipping container spray foam insulation for full details on specifications, use cases and the installation process.
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