Basement Humidity: Levels, Variations, Impacts and Controling

What is the Definition of Basement Humidity?

The definition of basement humidity is the percentage of water vapor content in the basement air space at the given temperature. Basement humidity is measured by the relative humidity (RH). The vapor water content varies with the basement environment temperature. A lower basement temperature can hold a lower amount of moisture, while a higher temperature can hold a larger amount of moisture in the air.

Basement humidity is categorized in different levels according to the related humidity level, such as lower level, ideal/correct/good or normal level, optimum level, and higher humidity level.

What Should Basement Humidity Be?

The basement humidity should be maintained between 30% and 50% relative humidity (RH) for a safe and healthy environment. This range protects both the structure and the people using the space.

• Humidity below 30% RH is considered too dry. It can cause wood shrinkage, cracking drywalls, and discomfort for humans due to dry air.
• Humidity above 60% RH is considered too high. It leads to mold growth, musty odors, paint blistering, and structural damage.

Basement humidity should not drop below 30% RH or rise above 60% RH under any condition. Both extremes lead to structural deterioration and unhealthy indoor air quality.

At Aqviz, we recommend adjusting acceptable humidity ranges based on seasonal changes:

• 30-40% RH is acceptable during cold winter months to avoid condensation on walls and windows.
• 50-60% RH may occur in humid summers, but anything above 50% should be managed with ventilation or dehumidifiers to avoid long-term moisture problems.

What is Lower Humidity Level in the Basement?

The lower humidity level in the basement is considered as between 30-40% RH . Lower humidity levels in the basement reduce the mold and mildew growth on the basement walls, floor, and fixtures. It helps avoid damage to furniture, wood, electronics, and walls from excessive moisture and wetness.

What is the Ideal Humidity Level in the Basement?

The ideal humidity level of the basements is between 30%-50% RH . The ideal humidity level in a basement refers to the most suitable relative humidity (RH) percentage that prevents mold growth, moisture damage, and poor air quality while maintaining comfort and protecting structural materials.

Optimum Humidity Level in the Basement: The optimum humidity level in the basement can be considered as 50-55% RH. The optimum humidity level in the basement is considered as the maximum humidity level without damage to the structure and health.

What is Higher Humidity Level in the Basement?

When the Basement humidity level is between 50-60% RH is considered a higher humidity level. A higher humidity level in the basement tends to grow mold and mildew, increase dust mites, and create condensation on windows. Prolonged higher humidity levels in the basement cause paint peeling, wallpaper bubbling, wood rotting, and material decaying over time.

What is Healthy Humidity Level in the Basement?

According to the National Asthma Council, the Article “Indoor humidity and your family’s health” in 2016, the healthy humidity level in the basement is recommended between 30-50% RH . This range helps to prevent dust mites and musty smells due to mold and mildew growth, which can cause many severe health problems, such as allergies, asthma, and an unpleasant breath to the user.

Correct, Normal, Good, Humidity Level in the Basement

Normal, correct, and good humidity levels are named as the same humidity level in the basement. The normal humidity level in the basement is between 40%-50% RH . A good humidity level in the basement is considered the humidity level in the basement that is good for both humans and the structure. It reduces the risk of mold growth, maintains air quality for breathing, and reduces the health impact due to dust mites.

How to Monitor Basement Humidity?

You can monitor basement humidity levels by following 3 ways.

• Use a hygrometer: Place a digital or analog hygrometer in the basement. It can measure the humidity levels and get accurate readings of basement moisture.
• Use smart sensors: Smart humidity sensors can sync with apps and give real-time humidity data and alerts if levels go beyond the ideal range.
• Use dehumidifiers with built-in sensors: Dehumidifiers have humidity sensors that can measure the humidity and automatically adjust to maintain the desired humidity.

What are the Reasons for Higher Basement Humidity?

Basement humidity level can be increased by these six factors, such as waterproof failure, basement cracks, seeping of groundwater and rainwater to the basement, poor ventilation, inadequate drainage systems, and underground pipe leakages.

1. Basement waterproofing failure: The basement humidity level can increase due to basement waterproofing failures. The basement waterproofing layer fails due to poor installation, lack of maintenance, poor quality materials, and poor surface drainage.
2. Basement cracks: Basement cracks increase the basement humidity by allowing moisture to seep in from the ground, eroding the wall’s structure. The basement cracks are formed by poor construction.
3. Groundwater and rainwater seeping into the basement: Basement humidity increases due to the seeping of groundwater and rainwater. Groundwater seeps in through cracks in the walls and floor or through thick soil settlement around the basement, especially in areas with annual rainfall over 40 inches a year.
4. Poor ventilation or lack of airflow: The basement humidity increases because of poor ventilation. The lack of airflow is caused by the lack of exhaust systems, clogged vents, neglect of maintenance, and insufficient windows, creating a lack of ways for water to escape, making the basement cool.
5. Inadequate drainage system: An Insufficient drainage system is another reason for an increase in basement humidity. Erosion of pipes, landscape issues, poor construction, and hydrostatic pressure are some reasons for inadequate drainage systems. With the lack of drainage systems, water has no way to drain away, increasing the moisture.
6. Underground pipe leaks: Underground pipe leakages increase the basement humidity. Due to clogged gutters, clogged drainage, and hydrostatic pressure, underground leaks occur. So the water accumulates in the soil around it and slowly gathers around the foundation, making its way inside the basement, creating a damp environment.

What are the Impacts of Basement Humidity?

The negative impacts of basement humidity rise when the humidity level drops below 30% RH and increases more than 60% RH.

Impact of Basement Humidity less than 30% RH

If the humidity level drops below 30% RH, it causes wood to dry out by cracking, shrinking, and splitting in floors, doors, and trim. And also it causes to form hairline cracks, shrink sealants, and inefficient heating due to dry air. As well as lower basement humidity affects negatively on humans by increasing respiratory issues, dry skin, scratchy throat, allergies, and asthma.

Impact of Basement Humidity more the 60% RH

If the basement humidity is increased more than 60% RH, it causes to increase the mold and mildew growth, wood swells, warps, or rots, paint peeling, blistering, drywall softening, efflorescence, surface water droplets, fast corrosion and respiratory issues, allergies, asthma, sinus issues, and other health issues to the humans.

Does the Finished Basement have Less Humidity than the Unfinished?

Finished basements have less moisture than unfinished basements. A finished basement consists of minimum cracks, a waterproof system, possessing an inside drain system, which means ensuring there is no excess water in the soil around the foundation. But an unfinished basement does not consist of these functions. Therefore, it is necessary to implement moisture control measures in the unfinished basement.

Can Basement Waterproofing Stop the Humidity?

No, only basement waterproofing does not stop the basement humidity problem. You should use other methods, such as installing sump pumps, installing French drains, using dehumidifiers, maintaining gutters and downspouts, and maintaining the grading of the land to stop the basement humidity.

Read more: How to Waterproof the Basement? Interior, Exterior, and Drainage

How to Control Basement Humidity?

To control basement humidity, you can waterproof the basement, install a dehumidifier, install a ceiling fan, improve basement ventilation, insulate the basement, and use moisture-absorbing materials in the basement.

Use moisture-absorbing materials in the basement: Basement humidity can be reduced and controlled by using moisture-absorbing materials in the basement. Using moisture-absorbing materials in the basement can reduce the growth of mold and mildew and prevent condensation. Moisture-absorbing materials like “humydry, silica gel, calcium chloride, baking soda, and activated charcoal” are placed in small open containers or distributed throughout the basement to reduce the humidity level.

Waterproofing the basement: Basement humidity can be controlled by waterproofing the basement. Basement waterproofing can prevent mold growth, increase usable space, and preserve the property value. You can use both liquid and sheet waterproofing membranes to waterproof the basement.

Install a dehumidifier in the basement: Installing a dehumidifier in the basement is another way to control the basement humidity. Using a dehumidifier improves the air quality, preventing musty odours. To install a dehumidifier, first choose a location that is easily accessible to a power outlet, then set the humidity level to 40-50%, which is the best setting that feels comfortable.

Install a ceiling fan in the basement: Basement humidity can be regulated by installing a ceiling fan in the basement. It is a cost-effective solution that improves the overall ventilation of the basement. Install a ceiling fan to keep the environment ventilated as less humid air blows onto the basement, quickly diffusing the rising moisture.

Improve basement ventilation: Improving the basement ventilation manages the basement humidity as it regulates the temperature level, making the environment comfortable for the occupants by getting rid of the musty smell. You can improve the basement ventilation by installing windows, ceiling fans, and exhaust fans.

Insulate the basement: Basement insulation helps to control the basement humidity. Insulation also absorbs sound, which results in reducing noise, and it promotes a comfortable environment with stable temperature and humidity, preserving the structural integrity. Insulating the interior walls with materials like rigid foam, installing vapour barriers along with insulation, and sealing air leaks are the methods used to insulate the basement.

Can Basement Humidity Affect the rest of the House?

Yes, higher basement humidity can affect the rest of the house. When the basement humidity is high, it produces mold and mildew growth that causes to musty odor. It can spread over the house and feel unpleasant in the house. As well as it cause to dust and mites, which can lead to respiratory problems and allergies. More than that, higher moisture can damage the structure by rotting, deteriorating, and decaying over time, which can reduce the structural integrity.

Related: Humidity and House Maintenance: Levels, Impact, and Control

Is 30% humidity too low for a basement?

Yes, 30% RH humidity is too low for a basement. The humidity level drops to 25-30% during the cold winter months. It helps to prevent mold or corrosion in the basement. But it is not good for the humans who live in the basement.

Is 50% humidity ok for a basement?

Yes, 50% RH basement humidity is ok for both humans and the basement structure. 50% RH basement humidity can prevent mold and corrosion in the basement and maintain the proper air quality in the basement for both humans and the structure.

Is 57 Humidity in the Basement High?

Yes, a 57% RH humidity level in the basement can be considered as a higher humidity level, but it is not extremely high. 57% RH will not be alarmed. But moisture-related issues can be visible when it is prolonged.

Is 60% humidity too high for a basement?

Definitely yes, 60% is considered too high for a basement. It tends to increase the mold growth, material deterioration, condensation, and musty odor in the basement. To prevent this, you should use a proper ventilation system, a dehumidifier, and seal cracks and damages in the basement that can leak water into the basement.

What is the Ideal Temperature in the Basement?

The ideal temperature for the basement is in the range 60-75˚F(15-24˚C), which is different with the country and the location. There are many advantages of having the basement at an ideal temperature, such as preventing moisture and Mold by keeping the ideal temperature consistent, offering a comfortable living environment, protecting structural integrity, and contributing towards the overall energy efficiency of a house.