How to Size a Dehumidifier

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Are you a bit confused on how to size a dehumidifier for your house? You’re not alone. You’re not alone. Even HVAC professionals often rely on calculations to determine the right size.

Managing your homes humidity levels is a crucial step in indoor air quality and comfort. Knowing the right formula or ‘rule-of-thumb’ before making that purchase on your dehumidifier key. You don’t want to miss the mark when it comes to buying one of these systems.

Now, there isn’t a strict formula how to size a dehumidifier since various factors will influence the capacity you need. The Association of Home Appliance Manufacturers (AHAM) provides some good general guidelines I’ve used over the years.

how to size a dehumidifier for your home

Below is a simple table and steps to use when selecting a dehumidifier capacity based on both the size of the area and the dampness level. Here is the simplified guide:

How to Size a Dehumidifier

Step 1: Determine the total square footage of the area you want to dehumidify.

Step 2: Assess the dampness level of the space:

  • Moderately damp: The space feels damp and has a musty odor only in humid weather.
  • Very damp: The space always feels damp and has a musty odor, and damp spots are visible on walls and floors.
  • Wet: The space feels and smells wet, and walls or floors sweat or have visible seepage.
  • Extremely wet: The space has wet floors and surfaces or standing water.

Step 3: Use this table to find the necessary dehumidifier capacity in pints per day (PPD):

Area (sq ft)Moderately DampVery DampWetExtremely Wet
50010 PPD12 PPD14 PPD16 PPD
100014 PPD17 PPD20 PPD23 PPD
150018 PPD21 PPD24 PPD27 PPD
200022 PPD25 PPD28 PPD31 PPD
250026 PPD30 PPD34 PPD38 PPD

Since these are approximate values, this is a spectrum you should aim for when shopping for a dehumidifier. It’s always a good idea to consult with a professional or manufacturer to ensure the dehumidifier you choose is appropriate for your specific needs.

Other factors like the number of occupants in the space, the presence of appliances generating moisture, rate of air change and the local climate will also influence required capacity. For an average homeowner looking to buy a small space or room dehumidifier, this should give you a clear target to start from in your buying search.

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