Drying Systems

An open drying system uses drier outdoor air to reduce indoor humidity levels.

Ventilation method

Open doors, windows and fireplace flues, and turn on exhaust fans to allow outdoor air to circulate indoors.

Humidity principle

Effective when the outdoor humidity ratio is lower than the indoor humidity ratio.

Dynamic equilibrium

Because indoor temperature and relative humidity are typically higher than outdoors, moisture naturally moves toward equilibrium, reducing indoor humidity.

Benefits

Simple and low cost, requiring no complex equipment. Even a short period of ventilation can lower moisture levels when conditions are favourable.

Considerations

• Ensure outdoor air has a lower humidity ratio and dew point than indoors.
• Open systems can lead to energy loss, especially in conditioned buildings.
• Open doors or windows may pose a security risk.
• Avoid ventilating when outdoor air is warm and humid, as it may worsen indoor conditions and prolong drying.