When designing ventilation systems it must be remembered that since most of the ductwork is installed within ceiling spaces, it is a good idea to liaise closely with the Architect at the early stages of design so that space requirements are met.

Figure 1 below shows a typical balanced ventilation system layout. One method, which can be adopted, is to run main supply and return ductwork in the ceiling space above corridors and the branches into adjoining rooms.

Ceiling heights in corridors may be lowered to accommodate larger ductwork.

It is common practice to use flexible ductwork to grilles and diffusers. These have several advantages; sharp bends are eliminated, flexible ductwork has better sound adsorption qualities compared to sheet metal, it is easier to install especially in a congested area and it allows more freedom in positioning the grille or diffuser.

A grille (plenum) box can be used to connect the ductwork system to the grille or diffuser. This has a larger cross sectional area than the connecting duct and reduces the air velocity before it enters the diffuser thus giving better air distribution over total diffuser area. A less expensive method is to use diffusers with factory-fitted square or round necks, which can be fitted directly to the flexible duct connection.

Each grille or diffuser should have a damper to regulate flow of air. This damper can be an opposed blade type incorporated within the diffuser or a butterfly volume control damper (VCD) positioned in the branch duct. All dampers require access.



Duct Guardian - Radius Elbow +ruters (turning vanes)
Radius Elbow - reduced height & depth

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