Specifications

16
Natatorium DesigN maNual
Condensation Control
You only have to enjoy a cold drink on a summer day
to experience dew point and condensation firsthand.
Condensation occurs because the surface temperature
on your glass is below the ambient dew point
temperature. While 50-60% relative humidity levels are
ideal for bather comfort and health they much higher
than people than what people are used to seeing in
traditional spaces in winter. In northern climates it is very
common to humidify in order to get the humidity levels
up to 30-40%. An indoor pool and humidified space can
experience condensation problems and serious damage
to the building structure in cold weather if they are not
designed properly.
Condensation is a major concern for all types of building
construction. Condensation triggers a destruction
process and allows mold and mildew to grow. If allowed
to occur inside the building walls or roof, condensation
will cause deterioration and can devastate the structure
by freezing in winter.
As previously mentioned, off-gassed chloramines have
a strong attraction to the airborne humidity and will
combine with moisture in the air. Consequently any
condensation in a pool, in addition to being destructive
on its own, could also be corrosive. It is critical that
condensation be avoided at all costs.
The building design and construction must be
appropriate to house an indoor pool. The envelope
design and construction must be suitable for 50% to
60% relative humidity year round.
A successful design will identify and blanket building
elements low R-values (typically exterior windows) with
warm supply air to prevent condensation. Window
frames and emergency exit doors must also be
thermally broken to avoid condensation.
Dew Point Temperature
The first step in condensation control is to establish the
space dew point temperature based on the owners
desired space conditions. With that information the
designer can establish potential condensation spots
in the building. A pool’s indoor design dew point will
typically range from 62-69°F (82-84°F 50-60%RH).
Contrast this to a typical space in winter that might be
70°F 40%RH which has a 45°F dew point.
Pools have a much higher likelihood of
condensation because of both an elevated
space temperature and slightly higher relative
humidity adding up to a very high dew point.
These are building elements with low R-values that
will have an inside surface temperature below the dew
point at winter design condition. Most importantly, the
dew point also establishes where to locate the vapor
retarder in the wall. Figure 6 shows that a typical pool
design of 82°F 50% RH has a dew point of 62°F.
Figure 6 – Dew Point Temperature