Dehumidifier Sizing

Written by Shannon Ward on . Posted in Guide

Dehumidifiers are useful units to keep at hand whenever the air humidity levels start to go off the charts and you start dealing with mold spores that rapidly spread in humid areas. Although this mostly happens in extreme changes of temperature and in rooms where condense is a common issue, like basements or bathrooms, you could also notice mold and mildew in the bedroom or living room. In order to get the best results, you need to know how to choose the right dehumidifier size because it’s essential to pick the one that can handle a particular room size or a certain level of humidity. The size doesn’t necessarily mean how large the dehumidifier needs to be but how much water it can absorb and how well it will handle a certain room area. Take a look at our dehumidifier sizing guide and keep this in mind next time you want to buy a dehumidifier.

Types of dehumidifiers

As you already know, the refrigerative dehumidifiers are by far, the most common types of dehumidifiers available in today’s market. They are most effective at high ambient temperature and high humidity. However, their effectiveness can be greatly reduced in colder climates. There are also the desiccant dehumidifiers which can do a great job of keeping a space dry and nice. These models pull in air and pass it over a desiccant material, such as silica gel which naturally absorbs moisture. Thanks to this technology, they don’t need to cool air before dehumidifying it. Since they are using an advanced technology, dehumidifiers mostly vary in size and strength. For example, most portable models are very lightweight and relatively affordable, being made from plastic. In fact, this is the type of dehumidifier that you will usually see in small places, such as a bedroom or kitchen. However, there are also some heavy-duty units, such as restoration dehumidifiers which are usually used to repair and improve heavy water damage caused by some natural disasters. Additionally, several manufacturers have built specially sized crawlspace dehumidifiers to address the humidity in storage areas and powerful dehumidifiers which are targeted toward the high humidity designed by some indoor pools and spas. Therefore, when it comes to types of dehumidifiers, it’s important to know that each one of these models will make your home healthier.

Measure the room

First things first, you need to calculate the surface of the room with mold problems to get an idea of how large the dehumidifier needs to be. Once you determine the size of the room, you must pair it with the capacity of a certain unit, which is measured in pints. The number of pints of water a dehumidifier can collect refers to its capacity to hold a certain amount of water collected from a room of a certain size. To measure the room, you need to multiply the length and width values which will result in square feet.

Monitor the air humidity

Another essential aspect in choosing the right size of the dehumidifier is how moist the air is so you will be able to find one that can handle that level of moisture. While some rooms might feel slightly damp, there are others with a high level of humidity hat exceeds the regular standards. The air humidity is measured in percentage and a normal level would be somewhere around 45-50% for you to feel comfortable and away from any mold risk. A room with an air humidity level above 50% will feel damp while levels over 70% are critical and improper for living. You can easily measure the air humidity with a device called hygrometer then use our guide to pick the right dehumidifier size.

  • For rooms of up to 300 sq.ft. and a humidity level between 50% and 70%, you must choose a dehumidifier with a 30-pint capacity;
  • For rooms of up to 500 sq.ft. and a humidity level between 50% and 70%, you must choose a dehumidifier with a 40-pint capacity;
  • For rooms of up to 700 sq.ft. and a humidity level between 50% and 70%, you must choose a dehumidifier with a 50-pint capacity;
  • For rooms of up to 1000 sq.ft. and a humidity level between 50% and 70%, you must choose a dehumidifier with a 60-pint capacity;
  • For rooms of up to 1500 sq.ft. and a humidity level between 50% and 70%, you must choose a dehumidifier with a 70-pint capacity;
  • For rooms of up to 300 sq.ft. and a humidity level between 75 and 100%, you must choose a dehumidifier with a 40-pint capacity;
  • For rooms of up to 500 sq.ft. and a humidity level between 75 and 100%, you must choose a dehumidifier with a 50-pint capacity or more;
  • For rooms of up to 700 sq.ft. and a humidity level between 75 and 100%, you must choose a dehumidifier with a 60-pint capacity or more;
  • For rooms of up to 1000 sq.ft. and a humidity level between 75 and 100%, you must choose a dehumidifier with a 70-pint capacity;
  • For rooms of up to 1500 sq.ft. and a humidity level between 75 and 100%, you must choose a dehumidifier with a 90-pint capacity or more;

Determine the air changes per hour in the room (ACH)

The air changes per hour refer to how many times the dehumidifier will have to collect all the air in the room and pass it through the filters in order to remove all the excess water vapors. If the dehumidifier is too small, it won’t be able to absorb all the air and remove all the moisture, so you should check its ACH level. In rooms with a humidity level between 90 and 100%, the ACH will be 6, in rooms with an 80% humidity the ACH will be 5, in rooms with a level lower than 70% it will be 4 and in rooms with a level under 60%, the ACH will be 3.

Calculate the cubic feet per minute (CFM)

The CFM level of a dehumidifier is related to how much air the dehumidifier is able to cycle. To determine this number, you will have to first multiply the height of the room by the number of square feet, which is the air volume in the room. Then, the resulted number will have to be multiplied by the ACH and divided by the number 60, which are the minutes in an hour. For example, if your room is 120 sq. ft. and the height is 8 ft., the air volume will be 960. Then, let’s say the room has an ACH of 5, meaning you will multiply 950 by 5, resulting in 4,800. Divide it by 60 and you will get an 80 CFM airflow for the dehumidifier. If you can’t find a dehumidifier with a CFM to match the needs of your room, you can always install more than one for the best results. Also, if the one chosen has a higher CFM than needed, it will run less in order to achieve the desired humidity level.

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Comments (6)

  • Jean

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    If my basement measures approximately 1000 square feet and it’s usually extremely humid, what is the ideal pint capacity for me to go with?

    Reply

    • June Spencer

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      We advise you to go with a model like the GE APEL70LT that has a generous 70-pint capacity. In case you want to see what other models would operate great in your basement, check out our article about the best dehumidifiers for basements.

      Reply

  • Edgar

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    How can I measure the humidity level to see which dehumidifier size I need?

    Reply

    • Shannon Ward

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      If you never had a dehumidifier before, it’s advisable to get a hygrometer that measures air humidity. This device is the most accurate help in monitoring air moisture and depending on its readings, you will be able to choose the proper dehumidifier size.

      Reply

  • Thelma

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    I have a 90-pint model I used for the basement but I no longer need it there for a while. Can I place it in the kitchen?

    Reply

    • Shannon Ward

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      In my opinion, the size is too large for a kitchen but this depends on how big your kitchen is. If the dehumidifier is too powerful and has a large capacity, chances are it will waste power because there will be little moisture for it to draw.

      Reply

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