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Zone 5 – Vapor Retarder on ceiling of indoor swimming pool

VerK9bECF6 | Posted in GBA Pro Help on

I an an insulator and a little confused on the subject of vapor retarders for ceilings. Normally we do not put a vapor retarder on the ceiling for Zone 5. But we are doing a job for someone that is enclosing their swimming pool and I am concerned that with that much humidity it might be necessary. They are installing an air-exchange unit of some kind but I do not have any details on that at this time. If this question has already been answered, can you please direct me to that thread?

Thank you

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  1. GBA Editor
    Martin Holladay | | #1

    Indoor swimming pools fall into a special category. Many of these buildings end up with condensation, rot, and litigation.

    Most building science experts, including Joe Lstiburek, have concluded that there is only one way to enclose an indoor swimming pool: put all of the insulation on the outside of the structure. In other words, build a PERSIST building. That'll keep you out of court.

    Here's an article on PERSIST: Getting Insulation Out of Your Walls and Ceilings.

  2. fpsco | | #2

    Also, they should provide a true pool room dehumidficaiton system like we do on commercial/instittutional pools. 6 ac/hr airflow rate. The unit should be capable of maintaining a room temperature 2 deg above pool water temperature and 60% RH on a degree day. You can get compressorized or ventilation only units. We have had good luck with ventilation only units with heat recovery. Also, they should take great care how the airflow where the airflow is directed, especially with windows and doors. Dectron has a decent guideline for an indoor pool. However, thier building wall descriptions are very weak. I would not use them for the wall design, strictly for the airflow/unit design.

    Also, make no mistake there is NOTHING green about having an indoor pool. At best, it's an energy pig that smells bad. If it is not designed, installed and maintained by people who know what they are doing, it can cause a host of indoor enviromental problems and destroy the building that encloses the pool.

  3. VerK9bECF6 | | #3

    Thank you for the input. All very interesting! We are not the builder on this project, we are just doing the insulation. The enclosure has already been built, but I do know they are still in the process of choosing a dehumidification system. I will pass this information on. Thanks again!

  4. wjrobinson | | #4

    Lisa, make someone else write the spec and guarantee the work. Best bet is to not take the job.

  5. user-1131006 | | #6

    I am working in zone 6 to prepare a room for an "endless pool" in a 150 year old asbestos shingled farmhouse "ell" between the house and barn. The existing room (2400cu ft) is below an unheated bedroom. . The walls are rough sawn 2x4 16oc. The concrete floor was removed (no insulation or vapor barrier underneath and too weak to support 3000 gallons of water) to prep for pouring new slab over 2" score board (1200 psf foam) with a vapor barrier on top of the insulation. One of the 2x4 walls was recent denseppacked with cellulose and two of the exterior walls have some fiberglass in them. Currently, the plan is to densepack the ceiling( 8"-10") and add 1" of foil faced polyiso (taped of course) to the existing drywall on the ceiling and wall and then cover all with Densearmour plus with latex paint over it. We will also be removing the FG and densepacking the other walls before the polyiso is applied. To control humidity, I am thinking of a ventilation only fan set to run continuously at 30cfm ( to keep pool negative wrt house) with a humidity sensing switch to run at full speed when the pool is in use. (pool is covered at other times) As there is no way to follow Joes recomendations in the referenced article I am wondering if this is workable or is there is a better way for this circumstance. The room has its own zone of HWBB heat.
    I contemplated using Panasonic' s ERV but don't think it is right for this climate. I don't think an HRV will suit our needs either as the room is small and wouldn't keep the room negative wrt house. I do not want to kill this house but the lady wants her pool. Recommendations are appreciated.

  6. GBA Editor
    Martin Holladay | | #7

    Good luck! I wouldn't take this job unless I could afford to hire a consultant from the Building Science Corporation to review and OK the plans.

    The walls and ceilings of indoor swimming pool rooms can rot very, very fast. A room above the pool? Cellulose insulation? I would run away from this job very quickly.

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