METRIC DESIGN GUIDE
Celsius is used for temperature designations in new or modernization building
projects. Renovation projects where the entire mechanical system is not to be changed
may retain Fahrenheit.
All major manufacturers of HVAC control systems offer products in Celsius.
Many manufacturers of diffusers and registers indicate they currently offer sizes to fit
a round metric ceiling grid.
Rectangular metal ductwork is a custom-made product. Typically, English-
dimensioned ductwork is only shown to the nearest 2-inch increment. Round metric
sizes are easier to measure (example: 300 by 600 mm) on a metric project.
Prefabricated flexible round duct is specified in converted sizes.
Units. See the ASHRAE SI Guide.