What Size Dehumidifier Do I Need For My Crawl Space?

Small crawl spaces can get stuffy quick because of the condensed air. Luckily, a good way to disperse some of that air and make the space more comfortable is by using a dehumidifier.

A dehumidifier cools down the air in the room to make it less stuffy. But there are certain sizes of dehumidifiers needed for different sizes of spaces.

A good rule of thumb for picking out a humidifier for a crawl space is the smaller the space is, the smaller the dehumidifier should be. For a crawl space that’s about 300 square feet, you’ll want a 20-30-pint sized dehumidifier. For a 500 square foot space, you’ll want a 25-40-pint dehumidifier. For an 800 square foot space, get a 35-50-pint dehumidifier. Finally, for a 1,200 square foot space, get a 50-60-pint dehumidifier. 

To determine which size humidifier is right for you, a short guide is provided below. 

Sizes of Dehumidifiers 

The size of a dehumidifier directly correlates with how big the crawl space being dehumidified is.

The typical size of a dehumidifier can range anywhere from twenty pints of water, to ninety pints of water.

You also want to consider the type of condition your crawl space is in while choosing the right humidifier. 

The smallest space size considered for humidifiers is about 300 square feet. This limits your size range to about 20 to 30 pints.

You’ll want to choose a dehumidifier that’s about twenty pints to thirty pints if your crawl space is either 200 square feet or slightly damp, at only about 50-60% humidity.

A twenty to thirty-pint dehumidifier is also a good choice for a crawl space that’s moderately damp, measuring at about 60-70% humidity.

If your crawl space is closer to 500 square feet, you’ll want a dehumidifier that’s closer to forty pints. 

But if you feel that you need something a little bigger, a fifty-pint dehumidifier is a good option for crawl spaces that are 800 square feet or have 70-80% humidity.

If your crawl space is either 1,200 square feet or flat out wet, which is about 80-100% humidity, a full-sized dehumidifier of sixty pints is the best option. 

As for the rest of the room sizes, the pint size goes up by about five or ten pints for every 200 square feet the room grows by.

That’s the simple rule to live by, but there is a more thorough way to find the right-sized humidifier. 

Dehumidifier and Room Size Calculations

The following are the main factors that should be considered when taking measurements of the room to find the right dehumidifier.

It’s a good idea to take these calculations to a professional, and they can also help you find the right-sized humidifier

The Volume of The Room Above the Crawl Space

The volume of the room above the crawl space is easier to get than the crawl space’s volume itself.

A lot of the general dehumidifier size versus room size charts are inaccurate in that they only have a few measurements of common sized rooms.

This might present a problem or two. For example, when you select the humidifier and you find that it isn’t filtering through all of the air fast enough, so the result is that the room still feels stuffy. 

To solve this problem, , find the volume of your chosen room based on the shape of it, and using the volume formula for that shape.

So, if your room is square shaped, use the formula for volume of a square.

To find the measurements, you can use a measuring tape that you can get at any hardware store and record the measurements.

You can then just use the chart to help guide you in picking the right sized dehumidifier.

You can use this method to find the size of the crawl space way more easily, since you don’t have to go on your hands and knees to find the volume. 

Room Square Feet 

To find the square feet measurements of the room, you only need to find how long it is and how wide it is.

Again, you can do this with just any standard tape measure and write down the measurements you get.

The amount of square feet in the space is the most important factor when deciding on a dehumidifier.

This is because of the rate of moisture that’s being taken out of the room.

Which is basically the amount of moisture the dehumidifier subtracts from the air in the crawl space within a 24-hour period.

The rate of this is more accurate and consistent if the dehumidifier is in the rightly sized crawl space.

If you aren’t sure if the dehumidifier will work fully in a crawl space, then always go for a bigger sized dehumidifier. 

Humidification Load 

The humidification load describes the amount of moisture that should be added to the air in the room to achieve a healthy level of relative humidity.

Humidity is caused primarily by building related factors. These can include everything from porous walls to structural dampness.

The level of humidity that’s considered normal is about forty to sixty percent humidity. 

Differences Between Crawl Space and Other Dehumidifiers 

While all dehumidifiers basically do the same thing, there are a few key differences between crawl space dehumidifiers and regular dehumidifiers. These include: 

They Come with Hygrometers

A hygrometer is what measures the current humidity levels of the room. This extra feature will help you monitor the air quality in the room. It will also help you evaluate your dehumidifier’s daily performance once you get it set up. 

Continuous Gravity Drainage 

Most dehumidifiers have a collection tank already installed in it to collect old water that you must empty regularly. But with a smaller dehumidifier, they usually come attached with a hose to the back that transfers the old water into the nearest drain. All you have to do is connect the hose yourself and make sure the dehumidifier sits above a drain so the water will flow downwards, letting gravity do the work for you. 

Internal Condensation Pump

An internal condensation pump is another option for continuous drainage. This option allows water to be drained anywhere with an ejection pump that comes with it. You can hook it up so that the water drains into any sink, no matter how far the crawl space is from the nearest sink.

Built-in Adjustable Humidistat 

The built-in adjustable humidistat will let you fully customize how your humidifier performs. For example, if you set the humidifier to reach a certain humidity level, which is usually about 30 to 40 percent, the humidistat will shut off automatically. 

Automatic Shut Off 

The automatic shut off system on crawl space dehumidifiers is designed to shut off once it senses that your water collection tank is full. This is to prevent overflow, and it alerts you when the tank needs to be cleared. 

Air Purification System

Finally, the air purification system is a filter that cleans the air as it passes through the humidifier. This will help you get cleaner air for your crawl space, which is especially important if it’s underneath the house. This is because air from these spaces tends to rise up to other parts of the house. So, if you have good air quality downstairs, you’re more likely to have good air quality upstairs as well.  

Final Thoughts 

Choosing the right sized humidifier for your room or crawl space will be a worthwhile investment for fresh, clean air in the long run.

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