Why is my house so humid even with AC running?

High humidity with AC running usually indicates your air conditioning system isn't properly removing moisture from the air, which can happen for several reasons including an oversized unit, dirty components, or ductwork issues.

The most common cause is an oversized air conditioning system. When your AC is too powerful for your home, it cools the air quickly but shuts off before running long enough to remove humidity. Air conditioners dehumidify by running the warm, humid air over cold evaporator coils, causing moisture to condense and drain away. If the system cycles on and off too frequently, this dehumidification process gets cut short.

Dirty or clogged components can also prevent proper dehumidification. A dirty air filter restricts airflow, while a dirty evaporator coil can't effectively remove moisture from the air. Similarly, a clogged condensate drain means the moisture your AC does remove can't exit properly, potentially backing up into your home. Low refrigerant levels will also reduce your system's ability to cool and dehumidify effectively.

Ductwork problems in Ottawa homes can contribute significantly to humidity issues. Leaky ducts allow humid outdoor air to enter your system, while poor insulation on ducts running through unconditioned spaces can cause condensation. Many older Ottawa homes have ductwork challenges that affect both cooling efficiency and humidity control.

In Ottawa's climate, summer humidity levels can be particularly challenging, especially during those muggy July and August days when outdoor humidity regularly exceeds 70%. Your AC should maintain indoor humidity between 30-50% for optimal comfort and to prevent mold growth.

Safety considerations include monitoring for mold growth in high-humidity areas and ensuring your condensate drain isn't backing up, which could cause water damage. If you notice musty odors or see condensation on windows even with AC running, these are signs that need immediate attention.

Next steps include checking and replacing your air filter, inspecting visible ductwork for obvious leaks, and ensuring your condensate drain is flowing freely. However, issues like refrigerant levels, coil cleaning, and system sizing require professional diagnosis. For a comprehensive humidity assessment and solution, consider having Ottawa HVAC Pro evaluate your system's performance and ductwork integrity.

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