How to Lower the Humidity Level of Your Basement

Are there musty smells, condensation, or visible dampness in your basement? This is a clear, practical guide on how to lower the humidity level in your basement.

1. Identify the Source of Moisture

Before trying to dehumidify, find out where the humidity comes from:

Leaking walls or floors → rainwater seeping through cracks.

Condensation → warm, humid air hitting cold basement surfaces.

Groundwater infiltration → poor drainage around the foundation.

Appliances or pipes → laundry, water heaters, or uninsulated cold pipes.

Fixing the source first is crucial — otherwise, dehumidification will only be temporary.

2. Improve Ventilation

Open vents or windows (if outdoor air is drier).

Install exhaust fans in laundry or utility areas.

Use a basement ventilation fan to increase air exchange.

Connect to HVAC ducts if your central system allows it.

Good airflow helps reduce stagnant humid air and prevents mold buildup.

3. Use a Basement Dehumidifier

The most effective way to lower basement humidity.
Choose a dehumidifier for basement according to the size:

Tips for optimal use of the home dehumidifier:

Set target humidity around 45–55% RH.

Keep doors and windows closed during operation.

Ensure proper drainage or continuous hose connection.

Clean air filters monthly for efficiency.

4. Seal and Insulate

Seal cracks in walls and floors with hydraulic cement or epoxy.

Apply waterproof coatings (like Drylok or cementitious sealant).

Insulate cold-water pipes to stop condensation.

Install vapor barriers on walls or under flooring if necessary.

These steps block external moisture and prevent humidity from rising again.

5. Manage Indoor Air and Heat

Keep the basement temperature above 18°C (65°F) when possible.

Run HVAC or space heaters occasionally to improve air drying.

Avoid drying clothes or storing damp items in the basement.

Warm air holds more moisture and promotes steady evaporation when combined with dehumidification.

6. Improve Outdoor Drainage

Sometimes, humidity is caused by external water infiltration:

Ensure gutters and downspouts direct water at least 3–4 feet away from foundation walls.

Grade the soil to slope away from the house.

Check for leaking window wells or poor waterproofing.

7. Maintain and Monitor

Use a hygrometer to monitor humidity levels regularly.

Keep RH between 40–55% year-round.

Inspect the basement dehumidifier performance and drainage every few weeks.

Summary Table