Ventilated Ceilings

INTRODUCTION

The Burgess Clip In tile system can be used to form an air-distributing ceiling when used in conjunction with a pressurised ceiling void. This is achieved by using perforated tiles throughout the ceiling and blanking off a quantity of tiles with a wrapped mineral wool insulation pad to achieve the required flow of air into the room.

The active perforated tiles are spaced evenly throughout the area to achieve the most effective distribution of air. These can, however, be located in specific positions if there are areas requiring targeted air flow.

As all tiles can be easily removed and repositioned, any future changes to the operating conditions can be accommodated.

PLENUM SIZE AND CONSTRUCTION

The size of the plenum will be governed by several factors including its shape and obstructions within it (e.g. beams, luminaries etc.). We would generally recommend that the depth of void be between 300 and 450mm. A reduction in the void depth may cause problems with regard
to airflow across the void space.

Responsibility for ensuring that the void is made as airtight as possible should be clearly defined and accepted by either the general contractor or specialist ceiling contractor. Any opening that could permit leakage should be sealed with materials impervious to the passage of air.

Care should be taken to ensure an equal distribution of air velocity over the opening and a highly directional air stream avoided by using vanes and splayed outlets.

The feeder ducts should be located at the most advantageous points with regard to air distribution and should be fitted with control dampers to enable the system to be balanced.
Deflector elbows should be fitted to the supply stub to direct the airflow towards the underside of the structure and prevent an induced airflow occurring at any nearby outlets or causing vibration or damage to the insulation material.

The maximum area, that can be served from a single supply point, is approximately 280 M2 for an unobstructed void space. The allowable blow distance should be from 13.5 metres up to 23 metres for a clear void space. Where more than one feeder is required they should be paced at no more than 15 metre centres.

VENTILATED CEILING CALCULATIONS

The following calculations are used to determine the number of active tiles required to provide a terminal velocity at head height of 0.2 m/s.
Remaining tiles, if perforated, should contain 25mm wrapped mineral wool pads which should be tape sealed to the non-engaging sides of the tiles.

Information required:

To determine the required throw of air into the room deduct 1980mm
(occupants head height) from the room height above.

Using the temperature differential (air supply temperature less the
room temperature), the conversion factor is determined from TABLE 1.

The design throw is calculated by dividing the throw by the conversion
factor.

The static pressure, based on the design throw, is obtained from
TABLE 2.

The total air leakage is calculated by multiplying the ceiling area by the
air leakage rate/m2 obtained from TABLE 3.
The total air leakage is deducted from the supply volume to arrive at the
total supply volume.

The active area required is calculated by dividing the total supply
volume by the air flow rate obtained from TABLE 3.

The active tiles required are calculated by dividing the active area
required by the individual tile area.

Static Pressure Differential Table 2

Air Flow Peformance - D320 Perforated Tiles Table 3

TYPICAL EXAMPLE