Indoor Pool - Unable To Control Excess Moisture In The Building

by Melina
(Hanover, PA )

We recently had the heater replaced in the indoor pool and the humidity is out of control. I do not remember it being this bad several years ago. The room has 3 sliding doors that we try and open when we are home, but the water pools by the doors and drips off the roof when we are unable to open the sliding doors. We have started turning off the heater because we are nervous that the excess moisture is going to cause serious damage.

I am not sure who to contact to find out what we need to do to improve this moisture content. Where we live we have several pool contractors that deal with outdoor pools but I do not see too much info on contractors dealing with indoor pools and the specific problems that can arise with indoor pools. We are getting desperate as we really want to enjoy the pool all year round. Any help and advice is really appreciated.

Hi Melina. This is a huge problem with many indoor pools. Condensation is a pool owner's worst nightmare. I've only dealt with one indoor pool, at the YMCA in Oregon when I was the pool operator there. It was a 100k salt pool. We had a situation exactly like yours and it cost them about $35k to fix. I learned alot by working with the guys for 10 days to fix the problem. I'm not saying this will fix your issue but it's a start.

Many times it's an issue of lack of engineering or installation errors. The Y issue was the pool area was getting old and was really not set up for an indoor pool.

Next is the vapor barrier which are sometimes not installed correctly. It's a thick plastic sheet that must surround the entire room(s). You want the heaviest polyethylene sheeting you can get. Yours might be too thin, not fitted correctly,
coming loose, splitting, etc... Check for those areas.

Cedar is a good wood to cover the vapor barrier. It's water resistant and repels water. Many homes are built with cedar closets, especially in humid areas. If you go the drywall route it must be an oil-based greenboard. This can withstand moisture.

Next are the doors and windows. They must be double or triple paned to reduce condensation. Single pane windows will guarantee condensation.

Then we have air distribution and dehumidification systems. They must be aimed the correct way toward the pool surface, not the walls. The air comes back and the dehumidification won't work. But the air can't be blown directly onto the water. This will cause more evaporation. Good air flow for a home indoor pool would be 10 - 40 feet per minute of airflow.

There's a balance between the water temp and air temp. This is normally a 2 degree difference. If you keep the air temp at 82 then keep the water temp at 80. Any larger spread than that and the evaporation rate increases and dehumidification calculations need to be revised to accommodate the difference.

And last is the fresh air/exhaust which is basically the opposite side of the same coin of dehumidification. Many times the duct work is too small to accommodate the moisture. The moisture might be destroying the duct system. If it's not exhausting the moisture out it's staying in the room. Also, some duct work may need to be high and at the floor to exhaust the out-gassing of chemicals. This is the "chlorine smell" you smell at many commercial indoor pools.

As for indoor pool contractors in your area, I have no clue. Perhaps you can start at your local indoor pool and ask the manager or pool operator if they know of or can recommend anyone. Someone in the area built the indoor pool.

Good luck and hope this helps.


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What Size Air Exchanger Do I Need

by Ryan
(Minneapolis )

We just purchased a home direct from the bank that has an indoor pool. The city inspector has told us that we need to get the pool house vented. How do we figure out what we need ? Can we just use world birds or do we have to get an exchanger? He just said as long as he sees a calculation from someone that is correct he is happy but don't know where to start.

I have been told I need a commercial HVAC company but i have read commercial exchangers are around $10k surely this is high for an indoor residential pool.

Pool itself is 15 x 27
Room is 24 x 42
Pitched roof

Hi Ryan. A good question that I've answered can be found here:

Indoor Pool Moisture

It goes into much detail about this issue.

Concerning your air exchangers, you would need one large enough to turn the air over 4 - 6 times. This comes from ASHRAE which stands for the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. The one that I'm most familiar with is Dectron Dry-O-Tron. They're the company the YMCA used when I was the pool operator there. We had to do a complete overhaul of the heating and exhaust system for the pool room a few years back and I learned alot working with those guys.

You can start with Dectron about your detailed questions. My understanding is commercial exchangers are considered for spectator facilities and need a turn-over rate of 6 - 8 times per hour. You shouldn't need that. With the information provided, I would think someone is trying to up-sell you something you might not need.

I always say that if I don't know the specific answer to your specific question, I can point you in the right direction to get your questions answered by the right people.


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