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How to Determine The Dehumidification And Ventilation Requirements For Your Indoor Pool Or Spa

Do you know which dehumidifier to use in your indoor swimming pool or spa room?

  • How do you know the unit you choose will handle your room?
  • Do you want to risk spending money on installation of the wrong sized dehumidifier for your environment?
  • Have salespeople told you it only depends on square footage of your pool?  Keep reading to find out what salespeople have not told you…

Determining the right dehumidification and ventilation systems for your indoor swimming pool requires several calculations to accurately find a solution to pool room humidity.  Trying to explain this process would take several thousand words and may leave you more confused than when you started.  Refer to the charts and calculation sheet below to help you understand the methodology of determining what your individual requirements are.

Isn’t there an easier way to determine dehumidification your indoor pool or spa area requires?

No, But… Click the orange button… and we’ll figure it out for you.  Answer as many questions as you can.  An engineer will review your answers and contact you.

Click for FREE consultation from an application engineer who will calculate your dehumidification requirements and help you choose the proper equipment.

Water Evaporation Chart

The chart below serves as a guideline to help determine the moisture load and dehumidification requirements for your pool room.  The chart is based on low pool activity and splash.  It is important to remember that during times of high pool activity, up to two times more moisture may be generated.

Pounds Of Water Per Hour Per Square Foot Of Water Surface

Pool Water Temperature

Air Temp RH% Dew PT 76 78 80 82 84 86 88 90 92 94 100
68°F 50% 49 0.028 0.031 0.037 0.038 0.041 0.045 0.049 0.054 0.058 0.063 0.079
60% 54 0.024 0.027 0.031 0.034 0.038 0.042 0.046 0.050 0.055 0.060 0.076
70°F 50% 51 0.026 0.030 0.033 0.036 0.040 0.044 0.048 0.052 0.057 0.062 0.075
60% 55 0.023 0.027 0.030 0.033 0.037 0.041 0.045 0.049 0.054 0.059 0.075
72°F 50% 53 0.025 0.058 0.031 0.035 0.039 0.042 0.047 0.051 0.055 0.060 0.076
60% 57 0.022 0.025 0.028 0.032 0.035 0.039 0.043 0.048 0.052 0.057 0.073
74°F 50% 54 0.024 0.027 0.031 0.034 0.038 0.042 0.046 0.050 0.055 0.060 0.076
60% 59 0.020 0.023 0.026 0.030 0.034 0.038 0.042 0.046 0.051 0.055 0.072
76°F 50% 56 0.023 0.026 0.029 0.033 0.036 0.040 0.044 0.049 0.053 0.058 0.074
60% 62 0.017 0.020 0.024 0.027 0.031 0.035 0.039 0.043 0.048 0.053 0.067
78°F 50% 53 0.025 0.028 0.031 0.035 0.039 0.042 0.047 0.051 0.055 0.060 0.076
60% 63 0.016 0.019 0.023 0.026 0.030 0.034 0.038 0.042 0.047 0.052 0.068
80°F 50% 60 0.019 0.022 0.026 0.029 0.033 0.037 0.041 0.045 0.050 0.054 0.071
60% 65 0.014 0.017 0.021 0.024 0.028 0.032 0.036 0.040 0.045 0.049 0.066
82°F 50% 62 0.017 0.020 0.024 0.027 0.031 0.035 0.039 0.043 0.048 0.053 0.069
60% 67 0.012 0.015 0.018 0.022 0.025 0.029 0.033 0.038 0.042 0.047 0.063
84°F 50% 64 0.015 0.018 0.022 0.025 0.029 0.033 0.037 0.041 0.046 0.051 0.067
60% 68 0.011 0.014 0.017 0.021 0.024 0.028 0.032 0.037 0.041 0.046 0.062
86°F 50% 65 0.014 0.017 0.021 0.024 0.028 0.032 0.036 0.040 0.045 0.049 0.066
60% 71 0.007 0.010 0.013 0.017 0.021 0.024 0.029 0.033 0.037 0.042 0.058
ASHRAE Recommended Conditions

Ventilation Chart

This chart can be used as a guide to determine the ventilation impact in your pool room.  The chart is based on an average 80% outside relative humidity.

Pounds Of Water Removed/Hour/100 CFM Of Ventilation

Outside Air Temperature

Air Temp RH -10 0 10 20 30 40 50 60 70 80
68°F 50% 3.0 2.9 2.7 2.4 1.9 1.3 0.5 -0.6 -2.3 -4.6
60% 3.6 3.5 3.3 3.0 2.6 2.0 1.1 0.0 -1.6 -3.9
70°F 50% 3.2 3.1 2.9 2.6 2.1 1.5 0.7 -0.4 -2.1 -4.4
60% 3.9 3.8 3.6 3.3 2.8 2.2 1.4 0.3 -1.4 -3.7
72°F 50% 3.3 3.3 3.1 2.8 2.3 1.7 0.9 -0.3 -1.9 -4.2
60% 4.1 4.0 3.9 3.6 3.1 2.5 1.6 0.5 -1.1 -3.4
74°F 50% 3.7 3.6 3.4 3.1 2.7 2.1 1.2 0.1 -1.5 -3.9
60% 4.5 4.4 4.2 3.9 3.4 2.8 2.0 0.9 -0.8 -3.1
76°F 50% 4.1 4.0 3.9 3.6 3.1 2.5 1.6 0.5 -1.1 -3.4
60% 4.9 4.8 4.6 4.3 3.9 3.3 2.4 1.3 -0.3 -2.7
78°F 50% 4.2 4.1 3.9 3.6 3.2 2.6 1.7 0.6 -1.0 -3.3
60% 5.1 5.1 4.9 4.6 4.1 3.5 2.7 1.5 -0.1 -2.4
80°F 50% 4.5 4.5 4.3 4.0 3.5 2.9 2.1 0.9 -0.7 -3.0
60% 5.5 5.4 5.2 4.9 4.5 3.9 3.0 1.9 0.3 -2.1
82°F 50% 4.8 4.8 4.6 4.3 3.8 3.2 2.4 1.2 -0.4 -2.7
60% 5.8 5.7 5.6 5.3 4.8 4.2 3.3 2.2 0.6 -1.7
84°F 50% 5.2 5.1 4.9 4.6 4.2 3.6 2.7 1.6 0.0 -2.4
60% 5.8 5.7 5.6 5.3 4.8 4.2 3.3 2.2 0.6 -1.7
86°F 50% 5.6 5.5 5.3 5.0 4.5 3.9 3.1 2.0 0.3 -2.0
60% 6.7 6.6 6.4 6.1 5.7 5.1 4.2 3.1 1.5 -0.9
88°F 50% 5.9 5.8 5.7 5.4 4.9 4.3 3.4 2.3 0.7 -1.6
60% 7.2 7.1 6.9 6.6 6.2 5.6 4.7 3.6 2.0 -0.3
90°F 50% 6.3 6.3 6.1 5.8 5.3 4.7 3.9 2.7 1.1 -1.2
60% 7.7 7.6 7.5 7.2 6.7 6.1 5.2 4.1 2.5 0.2
92°F 50% 6.8 6.7 6.5 6.2 5.7 5.1 4.3 3.2 1.5 -0.8
60% 7.8 7.7 7.5 7.2 6.8 6.2 5.3 4.2 2.6 0.3
94°F 50% 7.2 7.1 6.9 6.6 6.2 5.6 4.7 3.6 2.0 -0.3
60% 8.7 8.7 8.5 8.2 7.7 7.1 6.3 5.1 3.5 1.2
ASHRAE Recommended Conditions

Dehumidification and Ventilation Calculation Worksheet

Use the calculation formulas below to determine the dehumidification and ventilation needs for your indoor pool or spa room

A. Moisture load from the water surface

  1. Look up the lbs. per ft² per hour evaporation rate from the WATER EVAPORATION CHART using the desired pool water temperature, air temperature and relative humidity (RH) %______ lbs. of moisture load/ft²/hr x ____ ft² area of pool surface = ______ lbs./hr moisture load
  2. Covered Pool (pools that are uncovered less than 2 hours/6 hours______ lbs./hr moisture load x _____hrs/6 hours pool uncovered/ 6 hrs/day = _______ lbs. hr (average)

B. Exhaust ventilation to prevent moisture penetration of the structure and remove chemicals

  1. Calculate the natural air leakage
    1. Volume of pool space _______ ft length x ______ ft width x _______ ft ceiling height = _______ ft³ pool room volume
    2. Estimate natural leakage, air changes per hour (ACH)_______ ft³ pool room volume x _______ ACH natural leakage /60 min/hr = _______ ft³/min natural air leakage
  2. Exhaust air flow required to prevent moist air penetration of the pool room insulation.Recommended air exhaust rate 1.5 (minimum) times greater than the natural leakage rate of the structure.

    _______ ft³/min. natural air leakage x _______ (1.5) = _______ft³/min. recommended exhaust air flow rate to depressurize the pool room (prevents moisture penetration of the insulation)

  3. Indoor Pool Room Moisture Removed by VentilationLook up the lbs. of moisture removed per hour per 100 CFM of exhaust ventilation using the VENTILATION CHART at the desired room conditions.

    _______ lbs. moisture removed/100 CFM per hr of ventilation x _______ CFM of exhaust ventilation/100 CFM = _______ lbs. of moisture per hour removed by ventilation

C.  Determining the amount of dehumidification needed

  1. First method (uncovered pool or spa)Requires that the moisture removal rate equals the moisture load.  The RH is maintained with the exception of during times of high activity and pool splashing.  This may generate two times the humidity load.

    _______ lbs./hr moisture load _______ lbs./hr moisture removed by ventilation = _______ lbs./hr of dehumidifier capacity

  2. Second method (covered pool with low usage – less than 2 hours per 12 hours)Allows a rise in the RH levels when water is uncovered by providing a return to normal RH levels 2-3 hours after the water is covered.

    _______ lbs./hr average moisture load _______ lbs./hr moisture removed by ventilation = _______ lbs./hr, estimated dehumidifier capacity

If these charts and calculations leave you scratching your head, don’t feel alone.  Many individuals find it both too difficult and too time consuming.  Why risk making a mistake, when our engineers will do this work correctly for you for free… with guaranteed results.  Pick up the phone and call one of our experienced dehumidification engineers. 1-800-650-3528

One Response to “How to Determine The Dehumidification And Ventilation Requirements For Your Indoor Pool Or Spa”

  1. How to Correctly Size Your Swimming Pool Dehumidifier Says:

    [...] have contacted us, telling us things like "Wow, this seems like awfully hard work just to pick out a dehumidifier for my pool" (Tim Krieger of South Carolina). Well, it certainly can be and that’s why we are here. [...]

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