Should I keep my thermostat fan on or auto for humidity?

Author: Viviane Murray MD  |  Last update: Friday, December 12, 2025

Leaving your AC fan set to ON allows the moisture in your home to accumulate and reach mold-growing levels of humidity. To ensure that you and your family stay cool and healthy this summer, keep your AC thermostat fan setting to AUTO.

Should I set my thermostat fan to on or auto?

"ON" keeps the fan running continuously, which can help with air circulation and filtration but may consume more energy. Choose "AUTO" for energy savings and "ON" if you want constant air circulation or improved air filtration. Temperatures can soar or plummet depending on the time of year.

Does leaving an AC fan on increase humidity?

The indoor humidity increases because the air flowing from the fan re-evaporates the water remaining on the cooling coil after the air conditioner shuts off. This water, known as condensate, forms when humid house air passes over the cold cooling coil; the cold coil condenses the water vapor in the air to liquid form.

What should I set my thermostat to reduce humidity?

Thermostat - Automated Humidity Settings in Cold Climate
  • If outside temperature is greater than 20 degrees, humidity setting indoors should be set to 35 percent
  • If outside temperature is 10 to 20 degrees, humidity setting indoors should be be set to 30 percent

Is it better to have a fan on an auto or on?

Keeping your fan on AUTO is the most energy-efficient option. The fan only runs when the system is on and not continuously. There is better dehumidification in your home during the summer months. When your fan is set to AUTO, moisture from cold cooling coils can drip and be drained outside.

Should I set my thermostat fan to on or auto

Should the fan be on auto or on in winter?

When it comes to whether you should set your furnace fan to “on” or to “auto” in winter, the answer for me is “auto” because it's the move that has the most to do with energy efficiency. It is not, however, the only thing you can do this winter to bolster your HVAC system's energy efficiency.

What are the disadvantages of auto mode in AC?

AUTO Setting Disadvantages
  • Hot and Cold Spots. The air distribution throughout the house may be uneven, leaving some areas colder than others. ...
  • Limited Air Circulation. ...
  • Blower Fan Wear and Tear.

Which mode is best for humidity?

Dry mode is ideal for humid climates, offering enhanced comfort without the energy costs associated with complete cooling.

Is 75% humidity too high for house?

It is recommended to keep indoor relative humidity between 30 to 50 per cent, if possible. People typically find a relative humidity between 30 to 60 per cent most comfortable.

Does running a fan reduce humidity?

Turn on the ceiling fans: Keeping the air moving is an essential part of keeping excessive moisture away. Using ceiling fans, pedestal fans and other air-moving appliances can make a big difference and suck excess moisture out of the indoor air.

Does fan mode help with humidity?

Humidity Control: In conditions where the room feels stuffy but not hot, running the fan mode can help circulate air and manage indoor humidity levels.

What is the best AC setting to dehumidify?

Dry mode helps dehumidify your home, making it more comfortable and reducing the exhaustion and perspiration that come with high humidity levels. By drawing out excess moisture, this feature creates a cosy living space that's easy on the body. Say goodbye to the discomfort of a humid environment.

What is the best temperature to remove humidity?

Set the thermostat to a consistent temperature, even at 78°F, to keep humidity levels in check. Invest in a dehumidifier. Dehumidifiers are designed to extract excess moisture from the air. Place one in areas like bathrooms, basements, or laundry rooms for best results.

Is it OK to leave thermostat fan on?

If your system's fan is running without a break, the distribution of cool or warm air in your home will be more even. This lessens the likelihood of rooms without a thermostat being too cold or too hot.

Why is my AC constantly running on auto?

The Short Answer Is: When your air conditioning system keeps running and never seems to shut off, the problem could be linked to a number of malfunctioning components – frozen evaporator coils, a clogged air filter, a bad electrical relay switch that needs to be replaced, the fan blowing constantly, dirty condenser ...

Does auto mode in AC save electricity?

Yes, Auto mode is intended to save energy. The air conditioner can conserve energy and save you money on your energy bills by automatically adjusting the temperature and fan speed based on the ambient conditions and the presence of people in the room.

Why is my house always 70% humidity?

In a house, high humidity can be caused by poor ventilation, excess moisture from cooking or showers, leaks, or insufficient air conditioning.

Will mold grow at 75% humidity?

Mold requires both moisture and a food source to grow. When ambient relative humidity remains at or above 75% RH for a sustained period, conditions become ideal for mold growth. This elevated RH can result from extended periods of low temperatures or high moisture levels within the building.

Does opening windows reduce humidity?

Appropriate Ventilation

Ensure your house has enough airflow by opening doors and windows to allow a cross-breeze, installing ceiling fans, or employing exhaust fans in bathrooms and kitchens to reduce dampness. This maintains ideal humidity levels by letting damp air escape and allowing fresh air to flow.

How to set a thermostat to reduce humidity?

Keep the Right Temperature

During the summer, your thermostat should be between 72 and 78 degrees. If your thermostat has an “auto” setting, it can help cool your system's evaporator coils and dehumidify the air.

Does a fan dehumidify a room?

Although fans don't have any direct effect on humidity when it comes to removing it but do they provide proper and lot of circulation. The type of fan that is paired with dehumidifiers is called 'air mover' as they are very effective when it comes to removing or eliminating moisture.

Which mode in AC removes humidity?

By activating "Dry Mode", the AC system dehumidifies the air, removing excess moisture and creating a more pleasant and breathable indoor environment. Enhanced Comfort: High humidity can negatively impact the perception of temperature, making it feel warmer than it actually is.

Is it better to leave the fan on or auto?

AUTO is significantly more energy efficient between the two modes since the fan is only running when your AC is going through its cooling cycle. This takes less power, which is more budget-friendly, with some estimates showing you can save as much as $50 per month just by keeping your AC on AUTO.

Should I run my AC fan on auto or circulate?

Setting your thermostat to auto will allow your system to be more energy-efficient since the fan only runs when the system cycles on, not continuously.

Is it better to set AC to cool or auto?

In conclusion, auto mode in air conditioning not only helps save energy and reduce costs in the long run, but also improves indoor air quality, offers greater control and customisation, and can be more comfortable for the user.

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