Performance theaters are also referred to as legitimate theatres. Presentations can include dramatic productions like plays or musicals, ballets, films, operas, and concerts.
Older theaters, like movie houses, can be very elaborately decorated, and require great care in locating air distribution systems. They are different from movie theaters in several ways. Performances seldom occur one right after the other in a continuous loop like in movie theaters. Instead, performances are usually separated by several hours to allow the actors time to rest and eat in preparation for the next show. Most performances have a full or near-full house, and there are 15 to 20 minute intermissions midway through the performance for audience members to gather in the lobbies and socialize. Background noise control is also more important in a legitimate theatre than in a movie theater.
The principal areas of a theatre include the orchestra (main) seating section, balconies and boxes, the orchestra pit, lobby areas, box office and administration offices, and the stage. Other areas include the stage manager/prompter's station, the lighting and sound booth(s), the dressing rooms, the scene shop, and the wings (the areas to the immediate left and right of the stage; where actors and scenery wait for their cues to go on).
The stage itself provides a variety of unique challenges that include, but certainly are not limited to: if used, trapdoors in the floor; highly variable stage lighting; intricate, and oftentimes fragile, scenery and props; preventing curtains and visible scenery from moving when someone moves backstage; and, as always, moving sets and people around quietly in near total darkness backstage.
Because of the intermittent usage, theaters commonly experience a peak cooling load for only a few hours. A thermal, chilled water or ice storage system may be an excellent application. In addition to reducing demand, the chillers may not need to operate during performances, thus reducing noise interference. Because performances are separated by several hours, precooling may be viable, particularly for afternoon performances. Noise control in the main space is of utmost importance.
The cooling load occurring during the 10 to 15 minute intermissions, with people crowding into the lobbies for drinking and socializing, may set the design load. The density can be as much as 5 square feet per person.
The stage area presents several additional problems. The stage lighting is a major contributor to the high cooling load. Intricate, fragile, and varying scenery presents a variety of air distribution problems as well. In addition, actors can perform at widely varying levels of exertion that, when exacerbated by the heat from the unshielded stage lights, can add significantly to the already high cooling load. Lighting loads at stage level can be handled by exhausting air around the lights. Conditioned air is usually delivered, using numerous supply registers, from the low side and backstage area, with numerous return or exhaust registers at the lights. Low velocities are essential in order to keep scenery and curtains from fluttering.
Air balancing is also needed to avoid chimney effects that might cause the main curtain to billow when (if) lowered. Spot cooling may also be needed at the stage manager/prompter's station, and in the lighting/sound booth(s). Individual units are often used for the dressing rooms, if the rooms can't be supplied by the main air system and also have individual room control.
Loading docks adjacent to the stage need to be heated in cold climates. These doors may be open for long periods of time while scenery is being loaded or unloaded. Local codes should be followed regarding emergency exhausts or skylights, and for fire protection and safety requirements.
Most larger theaters use a central chilled/hot water system that serves air handling units for each zone. As a cooling load can exist all year long in many areas, air-cooled chiller packages that are located outdoors, isolated from the building and its occupants, and have no cooling tower are required. Low-ambient operation controls should be supplied. Variable speed drives on secondary water pumps further reduce operating costs. Air filtration systems of 25% to 30% pre-filters and 85% final filters are recommended.
If air supply is discharged at low velocity below people's seats, supply air temperatures below 65°F could create discomfort.
Energy Saving Recommendations
- Older and/or inefficient systems should be upgraded or replaced, particularly if CFC refrigerants are used.
- Renovate older buildings so that they have modern heating and cooling systems, and consider adding thermal storage.
- Retrofit systems with heat reclaim coils or air-to-air heat recovery devices. Such recovery devices can reduce energy consumption by transferring 40 to 80% of the sensible and latent heat between the exhaust air and supply air streams.
- Retrofit systems with a "free cooling" heat exchanger in a tower/chilled water plant system.
- Adding energy management systems with a central panel may allow individual air-conditioning systems or units to be monitored for maintenance and operating purposes.
Hot water is used for cleanup, dressing room showers, and restrooms. Hot water consumption varies significantly among individual facilities. If a restaurant is included in the building, it should be handled separately.
Water heating is not a major energy user. Most water heating is done separately from the building heating system and uses direct resistance or gas heaters, and, in some cases, point-of-use heaters.
Energy Saving Recommendations
If existing water heating systems are inefficient or inadequate, they should be promptly replaced with efficient, modern equipment. You may also wish to add timer controls and/or better insulation on storage tanks. The ASHRAE Applications Handbook chapter on Service Water Heating analyzes typical hot water use data as well as estimating procedures.
The majority of lighting tends to be incandescent, because of its dimming flexibility. Most stage lights are also incandescent for the same reason. The lobby area may have some fluorescent lighting, but most likely has incandescent spotlights.
Another reason that fluorescent lighting has is not commonly used in stage lighting is because of the strobing effect that results from the magnetic ballast. This effect is invisible to the eye, but can cause irregularities in film. However, the new electronic ballast has eliminated this effect and the use of fluorescents greatly reduces the heat given off by stage lights. A television station in Atlanta reduced their news stage lighting from slightly over 100 kW to slightly over 10 kW simply by upgrading to fluorescents.
Energy Saving Recommendations
All T-12 fluorescent lamps and magnetic ballast should be replaced with T-8 lamps and electronic ballast in the offices, restrooms, and common areas. Some of the spotlights in the office should be replaced with compact fluorescent spotlights. Replacing some of the stage lights with T-8 fluorescent lamps and electronic ballast should also be looked into.