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Calculation
Example:
Pool surface area 16’ x 32’ (512 sq ft)
*Indoor design air temperature 83 ˚F
Pool water temperature 81 ˚F
Relative Humidity 50 %
*Outdoor design air temperature 15 ˚F
* Always use design temperatures for indoor and outdoor air temperatures. Outdoor design temperatures
are published by organizations such as ASHRAE. Do not us day to day temperatures for this calculation.
1. From Table 1, select the appropriate evaporation rate based on the room air temperature,
water temperature, and relative humidity.
Evaporation Rate = 0.052
2. From Table 2, select the corresponding flowrate factor depending on the indoor air temperature,
outdoor temperature, and room relative humidity.
Flowrate Factor = 21.70
3. Multiply the values obtained from step 1 and step 2 to obtain the minimum CFM
required per square foot of pool surface area.
Evaporation rate X Flowrate = CFM / square foot of water surface area
0.052 X 21.70 = 1.12
4. Multiply the value in step 3 by the area of the pool
Area of pool X Value for step 3 = CFM
512 X 1.12 = 573
System Installation
It is necessary to design and size the duct distribution system for both the supply and the exhaust
air streams.
Proper duct design will
• Minimize air flow requirements
• Ensure a comfortable environment by using reheat if required
• Optimize humidity control, including eliminating condensation on windows by
blanketing the windows with airflow
Please refer to sketch 1 and 2 for typical duct layouts.
Note:
As a general rule, if the water temperature is maintained at
80˚F and the pool room air
temperature is maintained at 82˚F, use a factor of 1 cfm/sq ft of pool surface or .5 cfm/sq ft of room
area (whichever is greater) to determine amount of ventilation required.