What Size Crawl Space Dehumidifier to Get?

When a room has high levels of moisture, this becomes a breeding ground for milder or mold which may even lead to water damage occurring. Dehumidifiers reduce the moisture in the room’s air which protects electronics, clothing and wallpaper from being effected by moisture. It also helps avoid the musty smell that damp rooms tend to take on. Depending on the size of a room, a different size dehumidifier may be required. We will look at how to select the correct dehumidifier for your house with a nifty guide.

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How Do Dehumidifiers Work?
Dehumidifiers draw moisture from the air, this process regulates the humidity in the air. A fan will allow moist air to be pulled into the dehumidifier and pass through cooling coils. These coils will draw dampness out of the air via condensation. The dehumidifier then uses a heating system which then push dry air into the room to circulate. The water which was formed through condensation is then collected in a drip pan which is removable. Some higher end dehumidifiers have a tub which allows the water to be pulled outside or into a drain.

Air Changes per Hour and Humidity Level
The initial phase when selecting a dehumidifier is to determine the humidity level of the space you are planning on installing your dehumidifier. You should determine the air changes per hour that will be required based on the level of moisture in the room. The best and most accurate way to do this is by using a hygrometer which is relatively affordable. Most consumers go with a rule of thumb test.
The levels are as follows:
1) Moderate Dampness Level – The air has a musty smell and feels damp during humid weather – this requires 3 air changes per hour.
2) High Dampness Level – During any weather, the air will contain a musty smell and feel damp – this requires 4 air changes per hour.
3) Wet Dampness Level – mold or water damage is evident – this requires 5 air changes per hour.
4) Extremely Wet Level – Water is visible in areas – this requires 6 air changes per hour.

Crawl Space Cubic Feet
After the required air changes and the humidity levels have been determined, measuring the cubic feet that the dehumidifier is aimed at covering is the next step. In order to do this, you will need to multiply the length of the space by the height and then multiply it by the width.

Determining Air Flow
The cubic feet of air required to move every minute to ensure the space is dehumidified is known as air flow. The correct crawl space dehumidifier will ensure that there is enough power – without running 24-7 to maintain the correct cubic feet per minute of air flow, known as CFM.
The method for determining the CFM your crawlspace requires is as follows: multiply the air changes by the cubic feet of the space and divide that amount by 60. An example would be a space that requires 3 air changes hourly and is 3000 cubic feet would require and airflow of 150 cubic feet per minute.

Dehumidification
The job of the dehumidifier is of course, to remove sufficient moisture from the air in the room. This is measured by counting the number of pints of water it is able to remove from the air in that day, known as PPD. The range of PPD can be as low as 10 for a very low damp level in a small square foot spaces. The range can also hit high PPE levels of 51 for areas that are classified as extremely wet and have massive square foot spaces. The household habits, location of the home and climate are all factors in determining the PPD required for your dehumidifier.

Dehumidifier Types
A humidistat is something that many dehumidifiers come equipped with. A humidistat is able to set and measure the relive humidity – or rh – in a room. The rh fluctuates during seasons with 30 percent being ideal in winter and 50 percent being ideal in summer.
If high humidity is a problem throughout your entire house, then a whole-house dehumidifier is likely required. Many whole-house dehumidifiers can operate within your HVAC system whilst other dehumidifiers are portable.

An alternative to removing moisture through condensation is by using chemicals. Desiccant dehumidifiers use chemicals to dehumidify the air. These systems tend to have a scent in the air and are not as economical as the condensation systems. They do however, create lower humidity levels and are relatively more silent than condensation dehumidifiers.

Check the Moisture Level in the Room
A room that as a musty smell or is often plagued with damp surfaces would likely require a dehumidifier. A dehumidifier will work more effectively in a room which is mildly damp compared to one that is very wet. The best way to determine a room’s moisture is a humidity meter, however there are “rule of thumb” criteria which can be used.
Damp – in humid weather conditions the space feels clammy and smells musty.
Very damp – the space always smells musty and feels damp.
Wet – The space will regularly have visible condensation either on the walls or the ceiling.
Very wet – The space will constantly contain visible condensation on the walls/ceiling or have standing water.
It is important to note that if you identify moisture in the room, you should remove the water or repair the issue. This could be through cleaning the dryer’s lint flint or repairing any leaks you identify.

Room Conditions vs. Room Size
Merely identify the size and capacity of your space is not enough information needed to select the perfect dehumidifier for you. Considering the room’s actual conditions is a vital step in identifying the best solution for you.
The first thing you should do is determine how damp your space is, if your space is slightly damp then you could get away with just using rated capacity for your square footage. If you have determined that your space is extremely wet, you will need to look carefully into large capacity units and

T look at it from a logical perspective, a dehumidifier that is able to remove 50 pints of water from a room with less saturated air is not as powerful as a dehumidifier which can remove the same 50 pints of water in a room with standard conditions such as 60 percent humidity and 65 degrees Fahrenheit.

Additional Room Conditions to Consider
You will need to look at higher capacity units if any of the following factors apply to your space:
If there is a washing machine / dryer in the space, add 5 pints of water.
If the space has multiple people living in it, add 5 pints of water.
If the climate the room is located in is humid, add 10 pints of water.
If the space has many doors and windows, add 5 pints of water.

Other Factors in Choosing Dehumidifier Size
When selecting the size of the dehumidifier, consider these factors:

• If the climate the room is located in is humid, add 10 pints of water to the recommended capacity.
• If the space has many doors and windows, add 5 pints of water.
• If there is a washing machine / dryer in the space, add 5 pints of water.
• If the space has multiple people living in it, add 5 pints of water.

If you are considering a dehumidifier which may seem to exceed the requirements of your room, there are some advantages in doing so. If you select a more powerful dehumidifier, you can reduce electricity usage by running it on a lower level. If it is running on lower levels, it usually means that the dehumidifier will be quieter.
If your space continues to be humid, it becomes a breeding ground for mold, mildew as well as certain pests like spiders, roaches and other insects which enjoy moist conditions. In order to be the master of the humidity levels in your space, a correctly seized dehumidifier is all that you need.
Final Words
The best recommended way in fighting milder and mold is installing a crawlspace dehumidifier. When selecting a crawlspace dehumidifier, it is important to select the right capacity, if your capacity is too low, you will not be able to remove sufficient moisture from the air or prevent mold. The article explains the uses of a crawl space dehumidifier and assists in guiding you towards purchasing the perfect dehumidifier for your space.

Choosing the Unit
Chose the best crawl space dehumidifier based on the CFM and PPD. CFM is the movement of air in terms of cubic feet per minute. The PPD is the pints of moisture which can be removed from the air daily. The best dehumidifier will have CFM and PPD levels perfectly matched to your space requirements.
Some vital things to ensure are that the dehumidifier can operate in all temperatures and weather conditions as well as being energy efficient. It should fit correctly in your space and have drain capabilities.

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What Size Dehumidifier For a Crawl Space


300 sq. ft.500 sq. ft800 sq. ft.1,200 sq. ft.
Slightly Damp 50-60% Humidity
Air Feels Slightly Heavy
20 pint25-30 pint35-40 pint50 pint
Moderately Damp 60-70% Humidity
Occasional Musty smell
20 pint25-30 pint35-40 pint50 pint
Very Damp 70-80% Humidity
Wet spots on walls or floor
25 pint30 pint45 pint55 pint
Wet 80-100% Humidity
Seepage on walls & floor
mold may be apparent
25-30 pint35-40 pint45-50 pint60 pint

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