The Invisible Flood: Condensation in Steel Buildings

The roof doesn't leak, but the floor is always wet — that's condensation. In humid plants, solve it at design stage.

In food plants, farms and textile workshops, a strange thing happens on humid days: the roof doesn't leak, yet purlins and sheet undersides drip. That's condensation — warm humid indoor air meeting cold steel surfaces.

Fix it at design stage with three measures: size insulation to the local dew point (for high-humidity buildings, don't go below 75mm glass wool); add a vapor barrier on the liner side (aluminum foil or PVDC film) to stop moisture entering the insulation; and organize ventilation — ridge ventilators plus wall louvers to exhaust humid air.

For buildings already suffering condensation, adding liner insulation and ventilation costs far less than ignoring it — dripping condensate accelerates purlin corrosion.