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Vapor Barrier Placement part 3 in a 3 part technical series

Pool Design article by Kevin Ruddy, SWD Master


Place the vapor barrier as close as possible to the inside finish surface of all exterior walls and ceiling. Exact placement of the vapor barrier is critical. All materials on the pool side of the 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 (between insulation and drywall) and other areas (including ceiling) 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. Envelope the entire building interior with a continuous vapor barrier. Seams, gaps, tears, punctures, or breaches will permit moisture migration and must be avoided. Overlap (recommend overlapping 12" walls/ceiling) the material and 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, lighting fixtures should be surface mounted only if placed on surfaces that will incorporate a vapor barrier.

The effectiveness of a vapor retarder system may be greatly reduced if openings, even very small ones, exist in the barrier. Such openings may be caused by poor workmanship during application, poorly sealed joints and edges, insufficient coating thickness, improper caulking and flashing, and other factors. Air infiltration around a vapor retarder can carry considerable quantities of water vapor into the insulation, creating a condensation problem. The air finds passages through gaps in joints, tears in the barrier, or cracks where pipes or similar items penetrate the wall. Seal any necessary penetrations of the vapor barrier. To prevent moisture migration, use a suitable sealant/caulking material wherever any device (such as a nail, a screw, ductwork) unavoidably penetrates the vapor barrier. Patching - repair all tears and punctures with oversized patches of retardant materials and tape before vapor barrier is covered.

If you are not using a vapor barrier due to construction design (i.e. concrete block), then a high grade vapor barrier paint or waterproof paint must be used on the inside surface of walls and ceiling. (This paint is NOT enamel latex paint used in kitchens and bathrooms!) Ensure proper primer is used where required. Concrete block and other non-insulated type construction have little R-Value and are water permeable. If you are not using a Pool Cover, it will be imperative that you use some kind of vapor barrier paint if you cannot install this barrier between the insulation and finished wall. Also, note with concrete block, it has little insulation value. When cold outside air meets warm inside air (air infiltration through the concrete), you may have some condensation on concrete walls. With existing buildings like this, vapor barrier paint will be required to protect the surface, and no one can guarantee you may not see some "sweating" of concrete block. Ensure negative pressure is maintained within the environment.

Kevin Ruddy

Kevin Ruddy

Omega Pool Structures, Inc.
2091 Church Rd.
Toms River, NJ 08753
T (732) 255-0231 F (732) 255-2883