Condensation and mold in shops and offices: how to prevent humidity problems during periods of heavy rain

The recent weeks of persistent rain, high humidity, and snowfall across much of Spain are causing an increasingly common problem in shops and shopping centers: condensation buildup and mold growth on ceilings, ducts, fan coil units, and poorly ventilated areas.

Beyond being an aesthetic issue, excessive humidity can affect thermal comfort, indoor air quality, and the proper functioning of air conditioning systems.

Why does condensation appear in commercial premises?

Condensation occurs when humid air comes into contact with cold surfaces, such as:

• Diffusers and indoor units

• Poorly insulated ducts

• Glass facades

• Raised ceilings near the roof

During periods of continuous rain, the relative humidity outside rises, and if ventilation and dehumidification are not properly adjusted, the water vapor transforms into droplets that eventually generate:

• Damp patches

• Drips

• Damage to suspended ceilings

• An environment conducive to the proliferation of mold and bacteria

Risks of condensation and mold in shops and offices

The presence of condensation and mold in shops not only affects the image of the premises, but also causes:

• Health problems for employees and customers (allergies, irritations, respiratory problems)

• Persistent bad odors

• Damage to materials and equipment

• Potential regulatory non-compliance in indoor air quality inspections

How to prevent condensation and mold Mold in Commercial Air Conditioning

1. Relative Humidity Control

Maintaining humidity between 40% and 60% is key. To achieve this, it is essential to:

• Properly adjust ventilation systems

• Incorporate dehumidification equipment when required by the use of the premises or the climate

2. Insulation Inspection

Ducts, cold water pipes, and indoor units must be properly insulated to prevent cold spots where condensation occurs.

3. Maintenance of Condensate Trays and Drains

Clogged trays and dry traps are one of the main causes of:

• Dripping

• Odors

• Biofilm and mold growth

4. Adequate Ventilation

Insufficient ventilation increases the concentration of water vapor and CO₂. The use of heat recovery systems allows for air renewal without increasing energy consumption.

5. Monitoring During Periods of Extreme Weather

During prolonged periods of rain or damp cold, it is recommended to:

• Adjust setpoints

• Check airflow rates

• Verify proper condensate drainage

• Monitor indoor humidity

The Role of Preventive Maintenance in Retail

In chain stores and commercial spaces, a small humidity issue can recur in multiple locations if not addressed promptly. A preventive maintenance plan allows you to:

• Detect critical areas before mold appears

• Avoid complaints about leaks or unpleasant odors

• Protect your brand image

• Ensure compliance with the RITE (Spanish Regulation on Thermal Installations in Buildings) and indoor air quality standards

A well-designed, properly insulated, and maintained air conditioning system, along with adequate ventilation and humidity control, is the best way to keep your business in optimal condition.