Specifications

15
2.6.4 Exhaust Air. ASHRAE recommends
the room be maintained at 0.05-0.15” WC
negative pressure relative to surrounding spaces.
Ten percent more exhaust air than
outdoor air is a good
rule of thumb.
Figure 16 illustrates how the location of the
exhaust fan can also significantly improve the air
quality in the space. A spa or whirlpool should
have the exhaust air intake grille located directly
above it. This extracts the highest concentration
of pollutants before it can diffuse into the space
and negatively impact the room air quality.
Figure 16 – Exhaust Air Intake recommendation
2.6.5 Supply Air. ASHRAE
recommendations for proper volumetric air
changes per hour are important to ensuring that
an entire room will see air movement. Stagnant
areas must be avoided, as they will be prone to
condensation and air quality problems.
Short-circuiting between supply and return air
must also be avoided as it significantly reduces
the actual air changes within the space.
ASHRAE recommends:
 4-6 volumetric air changes per hour in a
regular natatorium.
 6-8 volumetric air changes per hour in
facilities with spectators
A quick calculation will determine the supply air
requirement. Nominal air flows from NE series
units are summarized in Table 3.
Supply air required (CFM) = [room volume (ft³) x
desired air changes] / 60
Model 1.0” ESP
004
2000
005
2500
006
3000
007
3400
008
3800
010
4600
012
5600
014
6400
Table 3. Nominal Air Flow Rates (CFM)
2.6.6 Cooling and Heating Loads. All
buildings should have cooling and heating load
calculations done to determine their specific
requirements. The room air temperature of an
indoor pool facility is generally 10-15 ºF warmer
than a typical occupied space. Therefore, the
heating requirement is larger than a traditional
room and the cooling needs are less.
 Rules of thumb do not apply. This is a
unique space that requires accurate load
calculations.
 Outdoor air must be included in load
calculations as it often represents up to 50%
of the heating load.
Space cooling is a free byproduct from packaged
dehumidifiers. These systems dehumidify by
cooling the air below its dew point. The
compressor heat can be used to heat the pool
water during this time or merely sent outdoors to
a condenser as is done with traditional air
conditioning systems. If the cooling load exceeds
the standard output of a dehumidification unit, a
larger unit with compressor staging is often
specified.
2.6.7 Outdoor Air. The introduction of
outdoor air is essential to maintaining good air
quality in any facility. The impact of outdoor air
ventilation on a natatorium changes with the
weather. Introducing outdoor air during the
summer adds moisture to the space and in the
winter removes moisture from the space. For
maximum dehumidification load calculation the
Summer Design conditions are considered.
Ventilation codes generally require that outdoor
air be introduced into a commercial building
during occupied hours. ASHRAE Standard 62-
1999 recommends the introduction of outdoor air
into a natatorium at the following rates:
 0.5 CFM/ft² of pool and (wet) deck area
 15 CFM per spectator.
Most designers use the larger of
the two values.
Seresco suggests that only the wet deck (a 5-6’
perimeter) be considered in this calculation, as
the purpose of this outdoor air is to help dilute
chemicals off-gassed from water. A predictably