Based on past experience and the weather data published by ASHRAE India chapter and ISHRAE, the outdoor design conditions for various seasons have been considered as follows:

Outdoor air requirement would be taken as 30 m³/h/person or one air change per hour, whichever is higher.

All sheet metal ducting complete with duct supports, turning vanes, canvas connections, erected in position shall be measured as per IS Standards and paid per unit area.  All dampers shall be excluded from the duct area.

n linear diffusers and grilles with box type damper shall be measured per unit area. The back up plenum shall be measured as additional sheet metal ducting.

Duct Work shall be measured on the basis of external surface area of ducts. Duct measurements shall be taken before application of the insulation. The external surface area shall be calculated by measuring the perimeter comprising overall width and depth, including the corner joints, in the centre of each duct section, multiplying with the overall length from flange face to flange face of each duct section and adding up areas of all duct sections. Plenums shall also be measured in similar manner

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