World wide free shipping on orders over 100€ - PayPal and Stripe payments - Made in Finland

Crawl Space Humidity: Unveiling the Hidden Threat Below Your Home

When it comes to maintaining a comfortable and healthy living environment, homeowners often focus on aspects such as temperature control, indoor air quality, and insulation. However, there’s a hidden area of your home that might be silently affecting all of these factors: the crawl space. Beneath your feet, this often overlooked space plays a crucial role in the overall well-being of your home, and one of the most insidious culprits that can wreak havoc within it is crawl space humidity.

In this comprehensive guide, we will delve deep into the realm of crawl space humidity – its causes, effects, and the array of solutions available to combat this seemingly invisible threat. By understanding the mechanisms at play and implementing the right strategies, you can ensure that your crawl space remains dry, structurally sound, and contributes positively to the health of your home.

From here you can read more about the problems a crawl space can impose.

Cracking the Code: The Causes of Crawl Space Humidity

To comprehend the challenge of crawl space humidity, it’s essential to first grasp the various factors that contribute to its emergence. The crawl space, often a dark and confined area beneath the main living areas, is uniquely susceptible to moisture-related issues. Here are some common causes that can lead to crawl space humidity:

Moisture Infiltration

Water has a tenacious way of finding its path into your crawl space. This can occur through foundation walls, the crawl space floor, or even from leaky plumbing pipes. Heavy rainfall, improper drainage systems, or grading problems around your home can exacerbate moisture infiltration, turning your crawl space into a damp haven.

Ventilation Woes

Traditionally, crawl spaces were designed with vents that were intended to promote air circulation and prevent moisture buildup. However, these vents can sometimes introduce more humid air from the outside, especially during hot and humid weather. Paradoxically, this can worsen the humidity problem rather than alleviate it.

The Condensation Conundrum

A significant temperature difference between your crawl space and the rest of your home can lead to condensation forming on surfaces within the crawl space. This can include pipes, ducts, and even insulation materials. As droplets accumulate, they create a fertile breeding ground for mold, mildew, and other moisture-related issues.

A wireless sensor monitoring basements temperatuer and humidity
RuuviTag in a crawl space.

Damp Soil Dilemma

The location and composition of the soil beneath your crawl space can play a pivotal role in moisture management. If your crawl space is built over damp or poorly drained soil, moisture can easily migrate through the floor and walls, adding to the overall humidity levels.

Unaddressed crawl space humidity can have far-reaching consequences that extend beyond the confines of this concealed area. In the following sections, we will explore the effects of crawl space humidity on your home’s structural integrity, indoor air quality, and your family’s well-being. Additionally, we will delve into a range of effective solutions that can help you regain control over this crucial yet often underestimated aspect of home maintenance.

The Ripple Effect: Unveiling the Effects of Crawl Space Humidity

The impacts of crawl space humidity are not confined solely to the crawl space itself; they can radiate throughout your entire home. Understanding these effects is paramount in realizing the urgency of addressing crawl space humidity. Let’s take a closer look at the potential consequences:

Mold and Mildew Onslaught

Excessive humidity creates an ideal environment for mold and mildew to flourish. These unsightly and potentially harmful microorganisms not only degrade building materials, but their spores can also become airborne, circulating through your home’s ventilation system and compromising indoor air quality. Prolonged exposure to mold spores can lead to respiratory issues, allergies, and other health concerns for your family.

Undermining Structural Integrity

Crawl space humidity can have a detrimental impact on your home’s structural integrity. Wood rot, a natural consequence of high moisture levels, can compromise the stability of floor joists, beams, and subflooring. Over time, this can weaken the overall structure of your home and necessitate costly repairs.

Inviting Pests and Critters

Damp environments are an open invitation to pests such as termites, rodents, and insects. These unwelcome visitors can cause further damage to your home’s structure, exacerbating the issues caused by crawl space humidity.

Energy Efficiency Takes a Hit

Your crawl space’s condition can affect the overall energy efficiency of your home. Damp insulation loses its insulating properties, and condensation on HVAC components can decrease heating and cooling efficiency, leading to higher energy bills.

Indoor Air Quality Challenges

The air in your crawl space doesn’t stay confined there – it can infiltrate the living areas above. Poor crawl space air quality can introduce musty odors and potentially harmful particles into your home’s breathing air, exacerbating allergies and respiratory problems for occupants.

What Are Acceptable Humidity Levels Inside a Crawl Space?

Acceptable levels of humidity inside a crawl space are approximately from 35% to 65% of relative humidity. In these conditions, the least amount of harmful things can happen. Keep in mind that relative humidity is relative to temperature. This means that if the space heats up or cools down quickly, it can have quick effects on relative humidity. Relative humidity can rise to harmful levels especially during summer, as warm air is entering the space and it’s cooled down due to the cooling effect of the ground.

What Happens if The Humidity Is Too High?

Mold and air pollutants can grow in humid spaces and you want to make sure not to give them a chance to spread around your crawl space. In most homes, the air inside crawl space ends up in the living quarters imposing problems to the indoor air quality.

Phone in front of ventilation hole oh a crawl space. Ruuvi's app is open on the phone displaying the temperature and air humidity of a crawl space.
Reading crawl space conditions on your phone is convenient.

Solutions That Stand the Test of Time: Battling Crawl Space Humidity

Given the far-reaching consequences of crawl space humidity, it’s imperative to take proactive steps to address and mitigate the issue. Here are some effective solutions that can help you regain control over your crawl space environment.

Crawl space encapsulation involves sealing the area with a durable vapor barrier and insulation. This prevents moisture from infiltrating the space, creating a dry and controlled environment. Additionally, a dehumidifier can be installed to maintain optimal humidity levels. 

Also, depending on your specific situation, you may consider sealing or closing crawl space vents to prevent the introduction of humid outdoor air. This strategy can be especially beneficial in humid climates. Proper grading around your home’s foundation and the installation of effective drainage systems can divert water away from the crawl space, reducing the risk of moisture infiltration.

Investing in a high-quality crawl space dehumidifier can be a game-changer. These units are specifically designed to handle the unique challenges posed by crawl spaces, ensuring that humidity levels remain in check. Tho keep in mind that regular inspections of your crawl space can help catch potential issues before they escalate. Promptly addressing leaks, water intrusions, or other problems can prevent long-term damage.

To be sure that everything is in good condition in your crawl space, you should install a crawl space humidity monitoring system in there. By having access to real-time data and data logs, you can rest assured that your crawl space is being monitored  constantly.

Ruuvitag: The Perfect Crawl Space Humidity Sensor

In the quest to maintain a dry, comfortable, and structurally sound home, the crawl space often remains an overlooked and underestimated area. Yet, this concealed space plays a vital role in the overall health of your living environment. One of the most effective tools for combating crawl space humidity is the RuuviTag – a versatile and reliable sensor that has proven itself as an ideal companion for crawl space humidity monitoring.

Understanding the RuuviTag Advantage as a Crawl Space Humidity Sensor

RuuviTag is a small, compact sensor designed to provide accurate and real-time measurements of various environmental parameters, including temperature, humidity, air pressure, and acceleration. This unassuming device has gained significant popularity in the realm of crawl space humidity monitoring, and for good reason.

The RuuviTag boasts impressive accuracy when it comes to measuring humidity levels. Its sensor technology ensures that you receive precise and reliable data, enabling you to make informed decisions about the moisture content in your crawl space.

Crawl spaces are often tight, confined spaces that require unobtrusive and space-efficient solutions. The RuuviTag’s compact design allows it to fit seamlessly into even the most cramped crawl spaces, ensuring minimal disruption to the area.

Installing the RuuviTag is a straightforward process. Its simple setup and configuration make it accessible to both tech-savvy homeowners and those less familiar with technology.

Three view from Ruuvi Station application.
These are some screenshots from the free Ruuvi mobile application.

RuuviTags features make it a solid guardian of a crawl space

One of the standout features of the RuuviTag is its wireless connectivity. Equipped with Bluetooth technology, the RuuviTag can transmit data to your smartphone or other compatible devices. This means you can conveniently monitor crawl space humidity levels from the comfort of your living room, providing real-time updates without the need for constant physical presence in the crawl space.

Crawl space monitoring often requires devices that can withstand extended periods without intervention. The RuuviTag’s long-lasting battery life ensures that you can rely on continuous monitoring without frequent battery replacements.

Receive alerts and examine history graphs

RuuviTag offers the flexibility to set up customizable alerts. When crawl space humidity levels deviate from your desired range, the sensor can send you notifications, enabling you to take timely action and prevent potential issues before they escalate. The RuuviTag’s ability to log and store data over time allows you to track humidity trends and fluctuations. This historical data can be invaluable when assessing the effectiveness of moisture control strategies and making informed decisions about crawl space maintenance.

When compared to other professional crawl space monitoring systems, the RuuviTag offers an affordable alternative without compromising on functionality or accuracy.

Take the Data With You to Wherever You Go

Ruuvi Gateway is a device making RuuviTags measurement data to the internet. More specifically to our cloud service, making the data accessible over the internet. If you want to receive alerts even though you go on for a trip, Ruuvi Gateway makes sure to let you know if something is not running smoothly.

Ruuvi Web App Dashboard for monitoring temperature online
From sensors, through Gateway to the cloud.

In Conclusion

The RuuviTag stands out as an exceptional tool for crawl space humidity monitoring. Its precision, reliability, compact design, wireless connectivity, and long battery life make it a well-rounded choice for homeowners looking to combat crawl space humidity effectively. By partnering with the RuuviTag, you can gain valuable insights into your crawl space’s moisture levels, take proactive measures to prevent issues, and ultimately contribute to a healthier, more comfortable home environment.

Buy a crawl space humidity sensor
RuuviTag helps you to monitor crawl space wirelessly

Buy a crawl space humidity sensor

RuuviTag helps you to monitor crawl space wirelessly


Tax 24% | 0%

Ruuvi is based in Finland. If you’re an EU consumer, VAT is included. If you’re a non-EU customer, you don't pay VAT. If you're an EU business, insert your VAT ID at checkout.

In stock

Add more for quantity discount!
Show bulk discount pricing table

Total: 39,90 + shipping


Add more for free shipping!

View shipping options

Made in Europe, Finland.
Worldwide free shipping on orders over 100 €.

RuuviTag is a Bluetooth sensor that monitors environmental conditions and sends the data directly to your mobile device. The Ruuvi Station mobile app allows you to view real-time accurate measurements and historical graphs. The app also provides customisable alerts to notify you of critical conditions, such as a melting freezer, excessively high bedroom temperatures that could disrupt sleep, or elevated humidity levels in your basement.

Onboard Sensors (4-in-1)

Temperature: °C, °F, K; typical accuracy ±0,2 °C @ 5-60 °C (±0.36 °F @ 41-140 °F).
Air humidity: RH-%, g/m3, dew point; typical accuracy ±3 RH-% @ 20…80 %. Range: 0-95 %.
Air pressure: Pa, hPa, mmHg, inHg; typical accuracy ±1 hPa. Range: 500-1155 hPa.
Motion: Movement counter. Counter is incremented when acceleration exceeds the threshold on any axis.

Operational Conditions

Operating temperature (with stock battery): -20 °C to +70 °C (-4 °F to 158 °F).
Absolute maximum operating temperature: -40 °C to +85 °C (-40 °F to +185 °F).
Housing: IP67, splash-proof, non-condensing location.
Battery: User-replaceable CR2477 (included). Supports extended operating temperature range battery CR2477T.
Battery lifespan: Estimated 12 to 24 months.
Bluetooth range: 5-20 meters (indoor), 20-100 meters (outdoor). The sensitivity of the receiving mobile device’s antenna, obstacles and wall materials affect the range. For increased range, use the Ruuvi Gateway router as a receiver.

App Features

Free and easy: User-friendly free app, signing in is optional.
Android and iOS.
Alerts: Configurable Bluetooth push alerts with customisable messages.
Real-time measurements: Track data in real time.
Historical data: Detailed historical graphs available for up to 10 days (offline).
History export: 10-day history export.
Dashboard: See all your sensors at a glance.
Personalise sensors: Use custom backgrounds and names.
Multilingual: Available in English, Finnish, Swedish, French, and German.


Integrations: Victron Energy, Home Assistant, Homey, and more.
Remote monitoring: When not within Bluetooth range, online remote monitoring is available with the Ruuvi Gateway and Ruuvi Cloud, both sold separately.

Technical Specifications

Data sheet: Download (pdf)
Read more info below:

What is an acceptable humidity for a crawl space?

An acceptable humidity range for a crawl space is typically between 35% and 65%. This helps prevent mold, wood rot, and pest issues while maintaining structural integrity and indoor air quality.

Is 70% humidity too high for crawl space?

Yes, a humidity level of 70% is too high for a crawl space. High humidity levels in the crawl space can lead to mold growth, wood rot, pest infestations, and other moisture-related problems.

Featured Products

Find the right products for your measuring needs
  • RuuviTag sensor measures temperature, air humidity, air pressure and motionIn stock
    Made in Europe, Finland. Worldwide free shipping on orders over...
    Read more

    RuuviTag Sensor (4in1)

  • Ruuvi KitIn stock
    Every Ruuvi Gateway product is shipped with...
    Read more

    Ruuvi Sensor Measurement Kit

  • Ruuvi GatewayIn stock
    Note! Every Ruuvi Gateway product is shipped with a...
    Read more

    Ruuvi Gateway Router

  • RuuviTag Pro 3in1 measures temperature, air humidity and motionIn stock
    Choose your model (2in1, 3in1 or 4in1) depending on...
    Read more

    RuuviTag Pro Sensor

    This product has multiple variants. The options may be chosen on the product page