LIGHTING indoor
swimming spaces has never been the easiest part of natatorium
design-although frequently, and with regrettable results, it has been
treated that way. With today's multipurpose aquatic centers frequently
accommodating diverse programming activities in a shared environment,
it has become an even greater creative challenge to get the light
right. But with proper foresight - including careful consideration of
the planned uses of the facility-aquatic facility designers can avoid
the glaring mistakes of the past and make certain people see
natatoriums in the best light possible.
Natural Light is
an increasingly attractive option for indoor aquatic facilities. Large
windows or open fenestration can be energy-efficient ways to supplement
artificial heat and lighting, and they add visual interest for users
and a much-appreciated connection to the outside for employees who work
all day in an enclosed environment. With all its advantages, however,
natural light can be accompanied by an undesirable partner-glare. Both
an aesthetics problem and a significant safety issue, glare from poorly
positioned window openings can turn competitive swimmers into
unidentifiable, anonymous silhouettes in front of coaches, spectators
and television cameras. Severe glare can make it difficult or even
impossible for officials to see beneath the surface to judge strokes,
turns, starts and finishes (this was a problem at the 1956 Olympics
venue in Melbourne, Australia). Far more seriously, recreational
swimmers beneath the impenetrable screen of a mirrored water surface
can disappear altogether from lifeguards' view.
Reflections occur when light rays hit a surface
and bounce off. The angle at which the ray hits the surface is equal to
the angle at which it bounces off. This angle is known as Brewster's
angle, and represents the point of maximum reflectance off the surface
of the object. We perceive the glare because of the highly reflective
nature of water and the sharp contrast between the light from the
windows or artificial light source and the relative darkness of the
surrounding walls, ceilings and floor.
The worst-case glare problems occur when viewers
-spectators, lifeguards or coaches-are positioned opposite windows,
wall openings or artificial lighting with the pool in between. The
light bouncing off the water surface causes viewers to squint and
strain to make out the silhouetted objects moving through the silver
reflections on the water.
Glare doesn't just occur, however, when the light
source is opposite the viewer. Contrasting elements of light and dark
can shed unwanted reflections on the water's surface any time the light
source is within the field of vision of the viewer.
Solving glare problems is frequently simple. If
light can be provided without the viewer experiencing light and dark
contrasts in his or her field of vision, the most objectionable glare
will be eliminated. The most common architectural solution in
constructing new competitive venues is to place the windows or other
fenestration behind the spectator sands so light washes over the
ceiling to the far wall and down to the pool deck (See Illustration 1).
By positioning the light source behind the viewers, out of their line
of vision, intense reflections and glare problems are avoided.
This is all well and good for new facilities, but
what about existing natatoria? Must they brick up their old windows and
blast new holes in the walls to resolve glare problems? Not at all.
With some creative cover-ups, almost any glare problem can be
significantly reduced and even eliminated.
Windows and open fenestration on opposite walls
can be controlled by constructing opaque walls, partitions (see
Illustration 2), facades, soffits or baffles (see Illustration 3) to
block the direct light, allowing indirect, deflected light to bounce
off the structure and spill into the natatorium space. In designing
these features, careful consideration should be given to wall coloring,
using combinations of light and dark surface areas to maximize the
effectiveness of the indirect natural light.
Glare caused by end-wall lighting is not as
severe as that created by opposite-wall lighting, but it can be a
problem, particularly for competitive swimmers performing the
breaststroke, backstroke or butterfly. An attractive solution to
end-wall lighting problems is a wall design using saw-tooth panels to
direct light away from the water (see Illustration 4).
Skylights are usually not problematic, since the
angle of reflection from an overhead source is normally not great
enough to be an issue (see Illustration 5). If glare compromises the
view from high spectator seating, however, a recessed clerestory can be
installed to achieve top-lighting with the same indirect benefits as
achieved with baffles (see Illustration 6).
If large, open windows are preferred for the
majority of the facility's programming, movable shades, shutters or
blinds can be an attractive alternative to permanent baffles. These
features allow direct natural light to brighten up the natatorium
during periods of daytime recreational swimming, while providing the
flexibility to shut out that light and any resulting glare during
competitive events.
No natatorium is
a natural beauty. In fact, many indoor aquatic facilities are
completely illuminated by artificial lighting, and all require some
kind of supplemental lighting for nighttime and special-even
programming. The proper choice and placement of artificial lights will
help lower maintenance and utility costs, and can both add to the
atmosphere of the facility and reduce or eliminate glare problems
caused by natural light.
While glare can be a problem with powerful,
improperly placed artificial lights, a more frequent concern is shadows
cast onto and beneath the water surface. Light fixtures suspended from
the ceiling over the deck are easier to relamp, but frequently cast
dark shadows from the pool edge that darken the walls of the pool
shell. Improperly placed overhead lights can also cast distracting
shadows from obstructing ductwork, structural beams and other objects.
The preferred positioning, then, for overhead
lighting in a competitive pool environment is directly above the water
surface. This is particularly important for pools without underwater
lighting. Light deteriorates in water at a rate of 50 percent in the
first foot; at a depth of 6 to 7 feet, the level of illumination has
dropped to as little as 10 percent of its intensity at the water''
surface. Casting light straight down penetrates the deep water most
efficiently and creates a minimum of shadows. At greater angles, more
light is reflected off the water surface, casting bigger shadows from
the pool edge and causing the bottom of the pool to appear darker.
Of course, lights placed over the water surface
can present a maintenance headache, since they can't be accessed easily
from a deck ladder or lift. This problem can be addressed by mounting
the lights on catwalks or providing access above the ceiling. Another
maintenance and liability headache-the potential for broken glass from
an exploded bulb to fall into the pool or onto the pool deck-is solved
by providing a lens covering on all fixtures. This creates a more
evenly distributed light and looks nicer, and also provides a barrier
between the lamp and the pool should the bulb break.
Underwater lights, required by code in some
jurisdictions, are helpful in brightening up the deep waters of a
competitive pool-but they can do much more than illuminate the water.
Underwater lights can reduce and even eliminate some moderate to severe
glare problems. If the physics behind this are difficult to see,
consider what a glass-front office building looks like at night. When
the lights are off inside the building, windows reflect the city lights
and structures nearby. But in those offices where the lights are on,
the reflections disappear, allowing us to see who's working the night
shift.
The same principal allows pool designers to
"bleach" out surface reflection by countering it with underwater
lighting, although glare can't be completely eliminated in this manner.
Glare reduction is dependent upon the intensity of the light above the
water and the relative strength of the underwater lights.
In contemporary free-form leisure pools, water is
generally much shallower-usually from zero to 3-1/2 feet. The light
placement issue in leisure pool environments is, therefore, not
penetration of deep water, but rather the creation of a mood. Thus,
underwater lighting in leisure pools is frequently tinted or positioned
to add character to the otherwise flat characteristics of the water.
Hand in hand with the issue of placement in the
light intensity required for various programming needs. Competitive
events will generally require a much greater intensity of light than
recreational or lesson programming. Among their rules and regulations,
governing bodies of various competitive organizations usually include
precise specifications for venue standards, including lighting
requirements. One hundred foot-candle (107 lux) illumination is
required at the water surface for U.S. Swimming and collegiate
championship events. For World Championships and Olympic Games, FINA
rules stipulate 500 lux illumination.
Obviously, to maintain these light levels at all
times would be a needless utility expense and an undesirable
environment for nighttime recreation programming and other
non-competitive events. Consequently, lighting is frequently designed
to perform a variety of functions. A flexible lighting system might
provide both indirect and direct lighting to be chosen alternatively or
in combination according to event requirements.
Lighting competitive events for television
coverage is a significant challenge, according to Steve Uline, director
of Bud Sports, a television production company that has covered
national and international sports competition for more than 15 years.
The company's typical lighting arrangement for indoor aquatic events
includes "quartz vapor lighting the full length of the pool on both
sides, so we can shoot 360 degrees without any shadows," Uline says.
"We block all windows and place our own lights high enough so we don't
have glare problems." The good news for facility owners planning to
host such events is that most television crews will have their owner
requirements and will therefore be prepared to provide their own
portable lighting to cover specific needs.
In leisure environments, opportunities exist for
much more flexibility and creativity in lighting design. Light
intensity at the water and deck surface is typically much more muted,
usually in the range of 20 to 50 foot-candles, and frequently consists
of a variety of spotlights, indirect lights and underwater lighting in
color ranges that provide more interest and excitement to the interior
environment. However, with the need for safety still paramount, family
aquatic center managers must keep on the lookout for "hot spots" and
"blind spots" that these lights can cause.
The final decision to make when lighting an
indoor aquatic space is the type of light source to specify. In leisure
settings, lighting choices may run the gamut from incandescent to
fluorescent, halogen and any of the high-intensity lighting choices.
For competition pools, however, high-intensity discharge (HID) lamps
are the preferred choice.
There are several types of HID lamps, all of
which operate on the same principle (light is produced from gas or
vapor inside an electrically charged arc tube). All are relatively
long-lived compared to other lamp choices, making them preferable for
difficult-to-access locations. But each has other advantages and
disadvantages that should be considered during the selection process.
Mercury vapor lamps, the first HID lamps
produced, feature low initial cost and a long lifetime, and produce a
white light that they retain well over time. While more efficient and
cost-effective lamps have since been developed, mercury vapor lamps
remain an option for locations where lamp replacement is difficult.
Metal halide lamps have a very high light output
and are considerably more efficient than mercury vapor lights. The
quality of the light is also typically very good, usually a clean white
light that delivers good color accuracy. Among their most significant
disadvantages are the long cool-down and warm-up time require between
start-ups. Metal halide lamps also must be shielded against UV
radiation emission and their color accuracy can shift over time.
Despite those drawbacks, the light quality and efficiency of metal
halide lamps continue to make them a preferred choice in many
applications.
High-pressure sodium lamps are also highly
efficient and long-lived, some lasting in the range of 10,000 to 40,000
hours. The conventional sodium lamp, however, produces a very warm,
golden light that may not be desirable in some applications. Newer
versions are being produced that create a whiter light, but these are
not as efficient as conventional high-pressure lamps.
Pool lighting
options are numerous and programming requirements, utility and
maintenance considerations, local codes and user-group stipulations all
have to be taken into account when deciding the positioning and type of
lighting components in a natatorium. A challenging job when the
facility is designed for a single category of users, it's an even
greater challenge when the mix becomes more broad-based, as is usually
the case with today's multipurpose facilities. And if there's one place
you don't want to skimp, it's in the lighting systems. It's not that
lighting system shortcuts will adversely affect the entire facility.
They'll just cast a bad light on everything the public sees.
Scot Hunsaker of Counsilman Hunsaker