2005 : Ventilation And Air Conditioning At The Plaza Theatre

Plaza 2K Logo

Other Pages:

Plaza's Hot History
The largest single project since acquisition and renovation of the Plaza Theatre was the installation of the ventilation system in 1997. During this work the theatre was dark for several weeks whilst the auditorium was filled with scaffolding, a significant amount of infrastructure was craned on to the top of the building and the roofline altered to permit installation of ductwork. As originally built the Plaza had a basically flat bitumen roof painted with silver to reflect some of the heat from the sun. In the middle of the roof were two ventilation fan towers joined together with a wooden structure known as the 'penthouse'. The cinema auditorium ceiling featured two circular grilles below these fan towers - when the Plaza was converted to the theatre we know today, the stage proscenium arch was set forward of one of these. The Plaza has always had a slow thermal change characteristic - taking a long time to warm up on winter rehearsal days and once hot, being very uncomfortable particularly during summer productions and three-performance-pantomime days.

Ventilation and Free Cooling
The roof realignment project of 1997 analysed the heat issues in the building and observed that, since RAODS audience-oriented use of the Plaza was principally a few hours of nocturnal and weekend time, the likely hours that might demand air-conditioning could be considered as less than 1% of a year (although of course comfort for these few hours in hot weather may be critical to ticket sales for a given production). Balancing the substantial installation costs against the available funds, the 1997 project designed a ventilation (fresh air) system that could be subsequently upgraded to give air conditioning (cool air). The ventilation sought to change the entire volume of air in the auditorium around six times per hour - taking away warm, damp air from over the audience and introducing fresh air from outside the theatre via ducts over the staircases. The control system allowed for pre-heating of fresh air in winter and for some mixing of fresh and re-circulated air to prevent wasting of energy at appropriate times. By definition a ventilation system can achieve a degree of 'free-cooling' - if the fresh air is cooler than the waste air (eg after sundown), some benefit may be experienced, depending on the difference between internal and external air temperatures. Under extreme circumstances the outside air may be hotter than the inside - running a 'ventilation-only' system then may subtract from audience comfort!

Science and Maths
Unlike turning on a light which immediately fills a room, ventilation and air-conditioning are complex sciences, since both require work to be done over a period of time to achieve the desired result. Often the environment has characteristics which act against the change which we are trying to introduce - with ventilation, human respiration will consume fresh air and with air-conditioning the warming effect of body heat will counter the coolness being introduced. Careful design seeks to achieve a cost-effective balance of capability versus demand. To achieve cooling by air-conditioning, energy must be invested in processing the fresh air. The exact amount of energy depends on the heat we are trying to counter. For a simple model, each human being can be considered to generate the same heat as a 100W light bulb - a full house plus cast and theatre staff is around 250 people or 25,000 Watts. Stage lighting comprises various devices: assuming there are 50 lanterns running at an average 500Watts each - this is another 25,000 Watts of heat. Altogether, this totals 50,000 Watts - no wonder the auditorium gets hot despite fresh air!

Hampshire's Coolest Venue?
The need for improved audience comfort was recognised, so having paid off financial commitments relating to the ventilation and roof realignment project, RAODS set about strengthening its funding base and designing the solution for the air-conditioning upgrade. Air Improve of Winchester worked closely with the Society to cost and plan the complex integration of fabrication, pipework, lagging and craneage required. The cost model devised helped to seek funding over a period of months such that the vision of an air-conditioned auditorium could be fulfilled before the summer of 2005.

Air Conditioning Upgrade
Starting in the early hours of the first day of April 2005, the custom made chiller unit and two compressors were craned onto the roof of the Plaza. The whole lift operation was completed in under an hour by Romsey Crane Hire. Special thanks are recorded to all those who lease spaces in the Plaza car park for their co-operation with the period of restricted access of which they had been previously advised. During the remainder of that Friday, engineers from VES of Chandlers Ford upgraded the ventilation drive system to ensure that extra thrust was available to counter the airflow drag created by the cooling coil assembly. On Monday 4th April the pipework assembly team commenced fabrication of the network of flow, return and balancing pipes that connect between the cooling coil and the external compressors. With intermittent rain during the week it was sometimes necessary to erect a canopy to keep water off the new equipment! Installation of the three-phase electrical power and control lines was also started. By the end of Tuesday, the electrical work was complete and the pipework was charged with nitrogen gas for an overnight pressure test. Wednesday saw commencement of the ductwork lagging to ensure that the chilled air will be correctly delivered to the point of application - namely the ventilation grilles above the auditorium side-steps. The success of the nitrogen pressure test meant it was now possible to introduce the cooling gas to the system. On Thursday morning the Trend engineer arrived to program the industry-standard system control unit with the required algorithms to operate the air-conditioning part of the plant at times when the outside air temperature is such that additional cooling would be needed. While the controller was programmed, the cooling lines were topped up to working pressure with the refrigerant gas and during the afternoon the system was commissioned. We are very grateful to Air Improve of Winchester for co-ordinating the design and installation of the upgrade - the months of careful planning having paid off greatly in the swift implementation.

Thanks and Credits
RAODS gratefully acknowledge the assistance of The Foundation For Sports And Arts for a funding loan during the repayment period for the Ventilation works and Hampshire County Council and Romsey LaRonde in helping to fund the Plaza's Air Conditioning upgrade project. The installation was managed by Air Improve of Winchester with the key ventilation and air-conditioning elements being fabricated by VES of Chandlers Ford.

Photographs
The selection of photographs below depicts the original flat roof of the Plaza Cinema, through the installation of the ventilation plant during the late 1990's, to the 2005 upgrade to true air-conditioning. All photographs copyright Michael J Smith.

Other Pages:

Forthcoming Productions

Archive Shows

History of RAODS

Plaza Theatre History

Hiring The Plaza

Return to Home Page