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Dew Point: Understanding the Impact on Your Crawl Space

Understanding the relationship between changes in season, geography, and dew point is crucial for maintaining a healthy crawl space environment. Managing moisture levels in your crawl space is important for maintaining the structural integrity and indoor air quality of your home. One critical factor that affects moisture levels in your crawl space is the dew point, which varies with changes in season and geography. Understanding the relationship between dew point and your crawl space is essential for effective moisture management. 

What is Dew Point?

Dew point is a term often used in meteorology that plays a vital role in understanding weather and climate. Essentially, dew point is the temperature at which water vapor in the air begins to condense into liquid water. When the dew point is high, there is a lot of moisture in the air. This can lead to uncomfortable and muggy conditions. Conversely, when the dew point is low, the air feels dry and comfortable. When the dew point is high, the air is saturated with moisture. This can cause problems like mold, mildew, and wood rot in crawl spaces. On the other hand, when the dew point is low, the air is drier, and it can help prevent these issues.

How Does Dew Point Feel?

ATMOX Picture of Man Standing in the Heat

The sensation of dew point varies based on its value. When the dew point is low, typically around 55°F or below, the air feels dry and pleasant. The dry air can make it easier for your body to sweat and cool down, making you feel more comfortable. As the dew point approaches 55˚F to 60°F, the air may have a hint of humidity but typically still comfortable. Dew points ranging between 60°F – 65˚F are becoming less comfortable. When it reaches 70°F or higher, the air can feel oppressive and muggy.

How Does Dew Point Change with Season and Geography?


Dew point varies with seasonal changes and geography. Seasonality plays a significant role in dew point because the amount of moisture in the air is directly influenced by temperature. In warmer months, the warmer air often holds more moisture, resulting in higher dew points. Conversely, in colder months, the air is generally drier, resulting in lower dew points. This is why summer months tend to feel more humid and stickier, while winter months are typically drier.


Geography also plays a role in dew point. Areas with higher elevations tend to have lower dew points because the air is cooler and can hold less moisture. In contrast, areas closer to sea level tend to have higher dew points because the warmer air can hold more moisture. 

In the different regions of the US, dew points typically tend to be higher during the summer months. However, there are still many days, even in the warmer months, when the minimum dew point falls below 60˚F. Even in Atlanta, GA, the minimum dew point will sometimes fall below 60˚F during the hot summer months.

These days provide an excellent opportunity to effectively ventilate crawl spaces and maintain a healthy and dry environment. By utilizing appropriate moisture control and ventilation measures, homeowners can take advantage of these beneficial conditions and effectively reduce crawl space humidity levels throughout the year. However, it is equally important to avoid ventilation in a crawl space during times with high dew points as this air can be detrimental.  

The Power of Outside Air

When air from an area with a low dew point is brought into a higher dew point area, it can be a drying agent. Similarly, an air conditioning system works by bringing in air from outside and cooling it down and extracting moisture from it. This process not only cools the air but also lowers the dew point, which makes the air feel less humid and more comfortable.

ATMOX Picture of Man Opening Window for Fresh Air

Furthermore, outside air can be a powerful tool for controlling moisture levels in crawl spaces when used at the right time. The air can act as a natural dehumidifier by exchanging out the air and reducing moisture levels. This is because when outside air has a lower dew point than indoor air, the outside air enters your crawl space and helps reduce the humidity levels inside. In these conditions, introducing outside air into the crawl space can significantly reduce moisture. It is an effective and energy-efficient way to manage crawl space moisture levels.

Combining Ventilation and Dehumidification

Dehumidifiers are a common tool for moisture control in crawl spaces. While dehumidifiers can be effective, they can also be expensive to operate and maintain. Furthermore, the dehumidifier may not be able to reach its target humidity level when temperatures are very cold. The dehumidifier must be able to cool the air in order to extract moisture from the air. In colder temperatures, a dehumidifier may struggle to achieve these targets. As a result, cooler outside air may be a preferable option for drying as it often has more effective drying power than dehumidifiers in these cold temperatures.

By combining the use of ventilation and dehumidification, homeowners can lower their moisture control expenses and tackle year-round moisture issues. Furthermore, by controlling the moisture levels in the crawl space, you can create a healthy and safe environment that promotes good air quality throughout your home.

Post Author: ATMOX TOM