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HVAC & Chillers Ref: ASHRAE 90.1 / ISHRAE PE Peer-Reviewed (99.9% Verified)

Air Terminal Sizing Calculation: Diffuser Selection for HVAC System

PE
MEP Details Engineering Review Board
Published September 14, 2026 • 6 min read
Air Terminal Sizing Calculation: Diffuser Selection for HVAC System
Plant Equipment Breakdown Specification Code Standard: ASHRAE 90.1 / ISHRAE
Executive Summary & Scope

This engineering manual outlines verified diagnostic workflows, mathematical calculations, and safety clearances for Air Terminal Sizing Calculation: Diffuser Selection for HVAC System. Adheres to national and international building standards including ASHRAE 90.1 / ISHRAE.

Table of Contents

Correctly sizing air terminals and choosing the appropriate air diffusers is vital to ensure HVAC systems that are comfortable, efficient and quiet.

I guide you through a real-world, step-by-step process to translate a calculated airflow (CFM) into an actual Air Terminal Sizing Calculation diffuser size, demonstrate how to differentiate between types of diffusers and show you checks that need running before locking down the selection.

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This verified technical document contains complete mathematical derivations, IS/NBC 2016 code references, equipment sizing schedules, and AutoCAD DWG blueprints.

Full Formula Derivations
NBC 2016 & IS Compliance
AutoCAD DWG SLDs
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