Considerable cooling effects can be achieved with the use of a dehumidifier in certain situations. Often found in basements (because of the cooler temperatures and higher humidity levels), dehumidifiers have a bucket or pan that can be periodically emptied. Most have an automatic shut-off when the container is full. Many units also allow for the attachment of a hose that can be run to a floor drain.

One downside of a dehumidifier is that it pumps out heat as a result of the dehumidification process. Generally this is minimal, and the dryer air offsets the additional heat gain.


Relative humidity and humidistats

Relative humidity (RH) is the amount of water vapor actually present in the air compared to the greatest amount of water vapor the air can hold at that temperature. The optimum RH level for a building is generally considered to be between 30% and 50%. Anything above this range may promote bacteria growth. For example; In Minnesota’s climate, during the heating season, humidity levels should be in the range of 30% to 40% RH to prevent window condensation.)

Many dehumidifiers include a built-in humidistat, a device that allows you to set the desired RH level that you would like for the room. Once the room reaches the desired RH level, the dehumidifier will cycle on and off automatically to maintain the level.

Energy Factor Related to Efficiency

The energy efficiency of dehumidifiers is measured by the energy factor (EF). In general, a higher energy factor means a more efficient dehumidifier. ENERGY STAR® models have an EF of at least 1.85 for units that remove less than 75 pints/day and 2.8 for units that remove from 75-185 pints/day.


Why is humidity bad?

High humidity in a home will cause the occupants to feel much warmer, due to simple laws of physics. The higher the humidity in the air, the harder it is for sweat on our bodies to evaporate, which is how we cool ourselves in warm conditions. Even a cooler environment, with high humidity, will feel clammy and uncomfortable – think of a cool, damp basement.

Additionally, high humidity coupled with warm temperatures contributes to the growth of mold and mildew, especially on cooler surfaces such as tile or foundation walls.

Controlling humidity through proper sizing and use of air conditioning equipment, along with use of dehumidifiers, can reduce the impact of humidity on occupants and their homes.


How do dehumidifiers work to achieve cooling effects?
Dehumidifiers work by removing excess moisture from the air, which can lead to a perceived cooling effect. As the air is dried, the heat energy is transferred from the air to the dehumidifier, resulting in a cooler air stream. This process is particularly effective in humid environments, such as basements, where the air is already cooler. By removing the excess moisture, dehumidifiers can make the air feel cooler than it actually is, providing a cooling effect without actually lowering the temperature.
What is the purpose of a humidistat in a dehumidifier?

A humidistat is a built-in sensor that measures the relative humidity (RH) of the air and controls the dehumidifier’s operation. It ensures that the dehumidifier turns on and off automatically to maintain a set RH level, usually between 30-50%. This prevents over-dehumidification, which can lead to dry air and discomfort. By regulating the RH level, the humidistat helps to optimize the dehumidifier’s performance, reduce energy consumption, and provide a comfortable indoor environment.

How often should I empty the bucket or pan of a dehumidifier?

The frequency of emptying the bucket or pan of a dehumidifier depends on several factors, including the humidity level, air flow, and dehumidifier capacity. As a general rule, it’s recommended to check the bucket daily, especially during periods of high humidity. Most dehumidifiers have an automatic shut-off feature when the container is full, but it’s still important to regularly empty the bucket to ensure continuous operation and prevent water overflow.

Can I connect my dehumidifier to a floor drain?

Yes, many dehumidifiers allow for the attachment of a hose that can be run to a floor drain, eliminating the need for manual emptying. This is particularly useful for applications where the dehumidifier is located in a remote area or where frequent emptying is not feasible. However, it’s essential to ensure that the hose is properly connected and secured to prevent water damage or leaks. Additionally, check the dehumidifier’s manual to confirm compatibility with floor drain connections.

How much heat does a dehumidifier typically produce?

The amount of heat produced by a dehumidifier varies depending on its capacity, efficiency, and operating conditions. Generally, a dehumidifier produces a minimal amount of heat, typically around 1-2 watts per liter of water removed. This heat gain is usually offset by the cooling effect of the dehumidified air, making the overall impact on the indoor temperature negligible. However, in extremely humid environments or during prolonged operation, the heat gain may become more noticeable.

What are some common applications for dehumidifiers in HVAC systems?

Dehumidifiers are commonly used in HVAC systems to control humidity levels in various applications, including basements, crawl spaces, and areas with high humidity. They are also used in industrial processes, such as food storage, pharmaceutical manufacturing, and data centers, where precise humidity control is critical. Additionally, dehumidifiers can be used in conjunction with air conditioning systems to improve indoor air quality, reduce energy consumption, and enhance overall system performance.