What It Takes To Produce a Condensation Resistant Swim Room.
Many people are interested in building an indoor pool for recreation, exercise, training, therapeutics, and just plain fun.  Although an indoor pool is beneficial to the human body and spirit, the environment it creates can be harmful (if steps are not taken) to the building envelope. As pool water evaporates, interior humidity levels rise significantly.  Not only is the resulting moisture uncomfortable, but also, if left uncontrolled, it can destroy most standard building materials. Latent moisture disintegrates gypsum materials, rots wood, rusts metal,
efflorescence and leaching of concrete and promotes the growth of unhealthy and unsightly molds. Highly specialized materials and methods of construction must be used to protect against deterioration of building components.  Before you begin the design of an indoor pool building, you should consult a licensed professional with experience in the design and construction of indoor pool enclosures especially in cold environments.  Careful planning, early trouble-shooting and proper building techniques and material usage should result in many years of enjoyment - free from the problems most commonly found at indoor pool spaces. I have been to many a space that was well intentioned to be nice but lacked the knowledge to deal with these factors. Some wound up in court disputes and inexperienced players payed. Here are some concerns and techniques we use in our indoor pool construction.



Proper dehumidification and ventilation are essential to both ensure that the indoor pool space is comfortable for its inhabitants, and to inhibit growth of mold and mildew.  As the air in an indoor pool becomes saturated with humidity from the evaporation of pool water, moisture will begin to condense on interior surfaces and will cause discomfort to those using the indoor pool.  Mechanical dehumidification and ventilation equipment should be used to remove this moisture from the indoor air and thus maintain desirable and comfortable levels of humidity.

There are different methods available to provide mechanical dehumidification.

One method is to use refrigeration, such as a heat pump, to wring the moisture from the air.  In this case, as the humid air is drawn across chilled pipes, the moisture condenses on the coils and is removed from the air.

Another method is to provide an air exchange.  This method exchanges moisture-laden indoor air with drier outdoor air.  A heat exchanger is used to recover the lost heat from the exhausted air.


Warm, humid air inside a pool building naturally migrates to the cooler, drier air outdoors.  As it does so moisture condenses in the exterior wall cavity, causing mold, rot, and deterioration of the exterior wall materials.  This effect is especially pronounced in colder climates, where the contrast between the humid indoor air and the dry exterior air is greater.  Proper selection, placement, and installation of a suitable vapor barrier can minimize this unwanted moisture migration.


Select and specify a vapor barrier with a permeance rating of 0.1 or less.
A vapor barrier inhibits moisture migration.  The permeance rating (perms) measures the amount of moisture that can migrate through a particular vapor barrier.  A vapor barrier with a permeance rating greater than 0.1.....the kind typically used in standard construction.....will allow too much moisture through it and is not recommended for use in indoor pool construction.


Place the vapor barrier as close as possible to the inside finish surface of all exterior walls and ceilings.
Exact placement of the vapor barrier is critical.  All materials on the pool side of a vapor barrier are highly susceptible to moisture damage.  Use only waterproof or highly moisture-resistant materials on the pool side of the vapor barrier.

Place the vapor barrier between the pool area and other areas of the building.
When adjacent areas without humidity control share interior walls with the pool enclosure, unwanted moisture may migrate to those areas and cause problems.  Incorporate the vapor barrier into the pool side of the walls or ceilings separating those areas.  Also, provide weather-tight passage doors between those areas.


Install a continuous vapor barrier.
Envelop the entire building interior with a continuous vapor barrier.  Seams, gaps, tears, punctures, or breaches will permit moisture migration and should be avoided..  Overlap the material or positively seal vapor barrier joints.

Avoid penetrations of the vapor barrier.
Design the building to avoid penetrations of the vapor barrier.  For example, electrical boxes and conduit for wiring, switching, and lighting fixtures should be surface mounted if placed on surfaces incorporating the vapor barrier.

Seal any necessary penetrations of the vapor barrier.
To prevent moisture migration, use a suitable sealant material wherever any device (such as a nail, a screw, or ductwork) unavoidably penetrates the vapor barrier.




Provide a direct flow of warm, dry air across all areas of glass.


Because the temperature differential is most extreme at exterior glazed areas, windows and glass doors are particularly prone to excessive condensation.  As part of the heating and ventilation system, all exterior windows and glass doors should be bathed in a flow of warm, dry air.  This will inhibit fogging of windows and deterioration of window and door frame materials. We have implemented better glazing techniques that increase the condensation resistance on them and eliminate the need to HVAC every window.


Maintain pool/air temperature differential.


Maintaining the indoor air at 2 degrees above the pool water temperature reduces evaporation of water from the pool.  Reduced moisture in the air will allow the dehumidification system to work more efficiently.


Pool Cover

Even apart from safety, a pool cover offers significant benefits.  When in use, a cover minimizes evaporation of pool water and reduces the need to operate costly mechanical dehumidification equipment.  It also allows the indoor air temperature to be set lower to reduce heating costs.  And, because a cover also reduces the heat loss from the pool water, less energy is expended heating the water.


Without proper installation, the best quality materials will go to waste.  Quality of workmanship is critical.  Most construction workers are not familiar with the specialized materials and techniques required for an indoor pool building.  Before construction begins, fully explain to each worker the extreme importance of these materials and their proper installation.  Carefully coordinate the work of different trades where they overlap.  Review construction and installation of materials every day, if possible, to find problems before they become hidden from view. Our experience is building a swim space in cold environments.


NJ Home Improvement Lic. #13VH05465000

© 2020