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What is the Best Humidity Level for a Basement?

What is the Best Humidity Level for a Basement?

According to the Cambridge dictionary, a basement is a  building’s floor partly or entirely below the ground. Basements have humidity issues that may affect your structure and your health. This invisible threat can lead to several effects like mold, fungal infestations, respiratory problems like asthma. Therefore, it’s so critical to understand the ideal basement humidity levels. 

The healthiest humidity level in a basement is around 50% though this changes with seasons 30-50%. The level can go much lower in winter than summer, and you even require a humidifier. So, depending on the season, there are ways of regulating the levels for your health benefits. 

Unfinished Basement Humidity Level

For a finished basement, the ideal humidity range is 30-50%. Thus, it’s in excess if the levels go beyond 60%. A building with 60 levels and above is too humid and will feel damp. The house will develop mold, mildew, and other fungal infestations if you take no action.

The rule for ideal humidity levels applies for both finished or unfinished basement levels. So, it’s best to understand the seasons and the humidity level present.

Ideal Basement Humidity Levels in Winter and Summer

 So, what is the basement humidity level in winter? Finished basements tend to dry out in winter, as humidity lowers below 50%. In cold areas where temperatures fall to zero, the level goes 30-50%. However, humidity drops to 20-30% in places below zero degrees. 

In areas with these low temperatures, the high humidity leads to ice formation in window sills and ventilation holes. This icy situation can damage your structure.

In summer,  humid levels should be 50%, but they can go higher depending on your location. The higher the temperatures, the higher your humidity level rises. However, if you live in areas where summer is hot and dry, the humidity levels get low than usual. Again, in summer with wet monsoons, the humidity may rise than average. 

That’s why there is a threshold level to guide you, depending on the season. For instance, if the level gets lower than 50 in summer, you have skin discomfort and a dry cough. But, again, it’s tricky to achieve 50% in summer, and you need to use some control measures like insulation. 

Lowering the humidity in the basement

Before learning how to lower this humidity, let’s find out the sources of this moisture. There are three sources where this humid comes from;

  • Water from rain or underground 
  • Interior humid from unvented clothes dryers, bathrooms, cooking.
  • Moisture from outside that enters and condenses the basement.

Ways of Lowering Humidity 

There are various ways to lower humidity; some are cheap and readily available. The main methods of regulating the humidity include;

  • Use a dehumidifier in the basement. It’s a portable tool and comes in handy in reducing humidity levels. The equipment pulls moisture from the air and turns it into droplets that you pour. Other cheap products that act as dehumidifiers are silica gel, rock salt, etc. 
  • Seal gaps or cracks on the walls and around windows using window caulk. Sealing will help reduce the moisture getting inside the rooms.
  • Have basement insulation, which minimizes heat transfer. This technique maintains a more constant temperature, and this reduces humidity. 
  • Evaluate the gutters, downspouts, and surface grading. These are the leading cause of excess moisture in the basement, so assessing them can permanently fix the excess humidity.
  • Reduce moisture creation. You should limit all the humidity activities like showering and cooking in the basement. Also, you can opt to use vented fireplaces instead of gas as it creates water vapor. 

Other methods that you can apply are as follows;

  1. Use of plants. There are unique plants you can use to lower the excess humidity in the room. These plants are as follows;
    • Peace lily- the plant removes moisture from the basement using leaves. It requires less sunlight for growth thus can survive in the basement. 
    • Reed palm originates from humid areas and does well in low light. 
    • Boston fern – it’s best in removing moisture though ideal in natural light. 
    • Cactus- best plant for any harsh condition and in removing excess moisture
  2. Damprid contains calcium chloride crystals. The crystals absorb the excess moisture in the air. However, it’s not best for all situations, and you should follow the given instruction carefully. 
  3. Silica gel contains silicon dioxide that absorbs moisture. You can place a few packets in a room to lower the humidity levels.
  4. Use a container desiccant. The desiccant applies the same concept as silica gel but now on a larger scale, especially during the shipment of containers. Place one in your basement and keep replacing it when full. 
  5. Charcoal briquettes can act as a natural dehumidifier. In addition, these briquettes can help absorb excess humidity and are affordable. 
  6. Use baking soda and keep replacing it after every 3-4 weeks. Then, place the powder in bowls and put them in the room. 
  7. Use rock salt and place it in an open container to fully expose it to the air.
  8. Install a fan—a fan won’t help lower moisture levels but can be of great use. Setting the fan at low speed improves airflow and moves wet air out of the room. So, this is best for use with another absorbing method. 
  9. Improve ventilation to help fix the humidity issue. These include the following;
    1. Opening windows
    2. Using portable fans
    3. Install ventilation fans, especially in wet zones in the room like bathrooms, laundries, or sinks. 

What Happens if Your Basement is too Humid?

High humidity in the basement can lead to the following issues;

  • Water trickling out of walls.
  • Standing water on the floor.
  • Saturated base basement walls; a ring of dampness
  • Damp, humid air, which is called musty
  • In summer, condensation on cold walls and floors occurs when warm air hits the cool walls in the basement, especially in bathrooms. 
  • Odor, mold, and mildew
  • Deterioration of carpet or wood.
  • Due to excess moisture, the rot and decay of wood headers, sill plates, and columns.
  • Staining and blistering of wall covering.
  • Efflorescence, spalling of concrete. Though it’s harmless, a white substance forms on the concrete, brick, or stone. 

The damp conditions aren’t healthy for your fabric and occupants. It causes the growth of mold and bacteria. The fungus causes the most significant problem as it releases spores that cause sneezing, coughing, itchy eyes or skin, wheezing and respiratory infections, as per the CDC. In addition, prolonged exposure to the fungus causes a weakened immune system, allergies, and asthma.


Humidity levels are very critical in the basement. If you think the room is getting too humid, it’s best to purchase a hygrometer to monitor the levels. Again, regularly cleaning your basement will eliminate the high growth of mold. However, the required solution is controlling the activities leading to excess moisture in the basement.

If possible, evaluate the basement gutters, downspouts, and the general drainage system in the structure. Moisture may be accumulating from external sources or internal and leading to the high humid conditions.