Book - School of Science and Technology

434 Air distributionenergy consumption and maintenance costs are usually less than when compared tohigh level supply systems.. Mechanical ventilation ± high level supply and extract. This system is usually selectedwhere a flexible space is required, seating is removable or where it is not feasible or costprohibitive to provide under seat plenums.. Natural ventilation. Supply inlets are usually provided by attenuated builderworkducts at low level and extracted by attenuated outlets at high level, relying on stackeffect to ventilate and cool the area. This approach has potentially the lowest runningcosts but may require a number of provisions to ensure adequate air flow rates and tolimit peak summertime temperatures. Particular considerations include providing suitableair paths, inlets and exhaust positions, solar protection, thermal mass exposureand night cooling.Control strategies include:. demand controlled ventilation and cooling depending on occupancy or carbon dioxidelevels. space temperature and humidity. time control. night time purging of the space and possible pre cooling of the structure.Television studiosThe general requirement is to provide a comfortable environment within the constraintsimposed by the production of television programmes. Specific issues that need to beaddressed include:. high lighting loads in studios. high occupancies for shows with audiences. rapid changes in load. variable operation times and periods. sensitivity to air movement and noise. high equipment loads in technical areas. critical areas requiring a high degree of reliability. multiplicity of studio arrangements. adaptability to respond to changing requirements.Air distribution strategies include:. Systems need to be able to cope with high loads and rapid changes in load. All airsystems are preferred because of concerns over water in the space and central plant ispreferred to local units because of maintenance access restrictions.. Whilst variable air volume systems may provide an energy efficient solution for studios,constant volume systems provide an even air flow and at a constant noise level whichmay be critical.. Blow through coils with airside damper control is preferred to waterside control torespond to rapid load changes. Steam injection is used for fast response to meethumidity requirements.. High reliability for critical area is normally provided by redundancy on individual unitsand/or the number of units provided. Dual power supplies and generator back-up arealso provided.