What Size of Dehumidifier Do I Need?

Posted by AlorAir Alex on

The first thing that anyone interested in purchasing a dehumidifier should consider is its size or capacity. Unfortunately, most people go ahead and buy the appliance without knowing its actual size, only to go back to the store complaining that they were ripped off their hard-earned cash.

What Does ‘Dehumidifier Size’ Mean?

Ordinarily, the physical dimensions of the clamshell or size of the dehumidifier are the first thing that will ring into their minds when a discussion about size comes up. If you one of them, you need to realize that you are very far from what is meant in this case.

Size or capacity is used to refer to how many pints of water the device can extract in a specified time duration. Often, it is measured in terms of Pints per Day (PPD). It follows that the referenced time interval is 24 hours.

Steps in Determining the Appropriate Size:

Determine the Relative Humidity of the Room

You can purchase a hygrometer or even rent one from a home improvement store to measure the actual humidity level in your room. While this first step is overlooked, at times you may perceive that the humidity levels are high, which may not be the case in real sense.

However, if a hygrometer may be inaccessible, you can observe the room for signs of dampness

If the room has puddles of water, it should be considered to be extremely wet. In such cases, the relative humidity may range between 90% and 100%.

Signs of mold, mildew or a musty smell may also be used as an indicator of high humidity

Measure the Square Feet of the Room

For this exercise, you will need to have a steel tape or a tape measure. Record the dimensions of length, width, and height. Using these dimensions calculate the area of the room.

Estimate the Air Changes Per Hour (ACH)

Air changes per hour, (ACH) are used to refer to the rate of air that is added or removed from a room as a function of the volume space. While the definition may seem rather complex, the process of determining the values is relatively simple.

For humidity levels between 90% and 100%, the ACH value of 6 is used in subsequent computations.

For humidity levels between 80% and 90%, use an ACH value of 5.

For damp areas (Humidity levels between 70%- 80%), ACH= 4.

If the humidity levels fall below 70%, ACH= 3.

Quantify the Amount of Airflow in Cubic Feet per Minute (CFM)

The airflow is determined by multiplying the volume of the room by the estimated value of air change per hour. The result is then divided by 60 minutes to obtain the amount of moisture that has to be removed

Need A Simpler Technique?

Association of Home Appliance Manufacturers developed a dehumidifier sizing table, which can assist buyers in estimating the right dehumidifier that can satisfy their needs. These capacities have been tabulated below

AHAM Dehumidifier Sizing Table
The condition of the Space

500 Sq. Ft.

1000 Sq. Ft.

1500 Sq. Ft.

2000 Sq. Ft.

2500 Sq. Ft.

Moderate damp space with a musty smell in humid weather

10 pints

14 pints

18 pints

22 pints

26 pints

Very moist space with smells and damp stains on walls and floors

12 pints

17 pints

22 pints

27 pints

32 pints

Very wet space with wet walls and seepage

14 pints

20 pints

26 pints

32 pints

38 pints

Extremely wet with wet floors and high-load conditions

16 pints

23 pints

30 pints

37 pints

44 pints


AHAM Measurement Corrections

It is important to realize that the measurements are an estimate according to AHAM calculations. However, real-life conditions may require different dehumidifier capacities. For instance, a 2000 square feet room may need a 30-pint dehumidifier if it has moderate dampness. However, if this very room is a basement, a larger dehumidifier may be required. That is because conditions such as temperature and humidity levels may slightly differ from the rest of the room.

Still Not Sure What Is Best For You?

The best way to determine the capacity that suits your needs is to consult a reputable dehumidifier dealer. Some reputable companies such as Alorair are always open to giving consultation, and they actually respond to queries. You can find them by sending an email to slaes@alorair.com for reliable information regarding dehumidifier capacity and any other relevant questions you may have.


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