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We are a senior community with an indoor pool , when not in use covered by a bubble roll-up when not in use. The room temp is 84 degrees and the water temp is 86 deg. we have window condensation and what I suspect is early mold in spots on the walls. The temp used to be 82-84 deg., but some members wanted it warmer. Can you give some guidance on the relationship between water temp. and air relative to condensation?
Thanks, Mike Courtney - 253-838-1475

Your problem is that the dewpoint of the air is higher than the temperature of the windows and walls. The dewpoint is high because the spa keeps evaporating water due to its high temperatue. Covering the water helps reduce evaporation a lot, but in a closed room, any evaporation builds up. The solution is to provide some ventilation bringing in dry air and exhausting the high humidity air. If it is cold outside, this can be a significant energy drain. You can reduce the energy loss with a heat exchanger.

BAF

One way to help reduce the humidity problem is to raise the air temperature a couple degrees above the water temperature. This will reduce the evaporation significantly. It is also usually cheaper to heat the air than it is to heat the water above the air temperature, thus a small savings on the heating bill.

Remember heat wants to move from the warmest object to the less warm. Water does this by evaporation. If the air is warmer, the heat will move from the air to the water... reduced evaporation.

Steve Keifer

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Steve Keifer

Stephen, Thank you for your reply, and advice.
Mike Courtney