HVAC - How to Size and Design Ducts - Course M06-048

Nov 4, 2026

HVAC air distribution ductwork is critical to system performance and comfort. The course explains how properly sized and designed ducts ensure required air-flow delivery to specific locations while minimizing combined initial costs, fan operating energy, and building space usage. It addresses duct air-flow fundamentals, key pressure definitions (gauge vs. absolute), and the need to control noise transmission and indoor air quality. It also covers engineering tradeoffs such as larger duct investment versus lower long-term fan energy costs, along with systematic layout and design principles.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages91

Reading Time3 h 49 min

AccessFree to download

Ductwork Design Principles

Basic Definitions

Air Flow Principles

Total Pressure, Velocity Pressure, and Static Pressure

Air Flow Characteristics in Duct

Duct Components & Materials

Duct Classification

Velocity Classification

Pressure classification

Velocity classification v/s Pressure classification

Duct Shapes

Round Ducts

Rectangular Ducts

Oval Ducts

Equivalent Diameter

Duct Sizing

Equal friction method

Velocity Reduction Method

Static Regain Method

Pressure Losses in Air Distribution System

Duct Friction Losses

Duct Fitting Dynamic Losses

The Concept of Duct Equivalent Length

Pressure Loss across Components

Fan Sizing

Fan Selection Example

Balancing Air

Fan System Effect

Supply Duct System

Extended Plenum Systems

Reducing Plenum System

Reducing Trunk System

Spider System

Radial System

Perimeter Loop System

Rules of Duct Design (ACCA Manual D – Residential Duct Systems)

Return Duct Systems

Distributed Return

Central Return

Pressure Balancing

Duct Fittings and Terminal Units

Duct Fittings and Transitions

Volume Control Dampers

Fire and Smoke Dampers

Diffusers, Grilles & Registers

Location of Air Inlets and Outlets

Duct Construction & Reinforcement

Duct Construction

Duct Sheet Metal Thickness

Aspect Ratio

Standard Duct Sizes

Duct Fabrication and Lengths

Duct Hanger Spacing

Good Engineering Practices

Energy Conservation

Good Engineering Practices for Designing Ductwork

Ductwork Insulation and Sealing

Ductwork Insulation

Ductwork Air Leakage

Duct Leakage Tests

Duct Sealing

Duct Attenuation and Noise Considerations

HVAC Noise Points

Acoustical Analysis of a Ductwork System

Ductwork Testing & System Performance

Balancing the System

Testing Methods and Equipment

Air Flow Measurement Instruments

Determining Air Flow at Grilles

Determining Air Flow in Ducts

Provisions during Design for Testing, Adjusting, and Balancing

Duct Cleaning

Duct Cleaning Methods

Coordination between Design Specialties

| | | --- | | HVAC – How to Size and Design Ducts
Course No: M06-048
Credit: 6 PDH | |
A. Bhatia | |

Continuing Education and Development, Inc.
P: (877) 322-5800
[info@cedengineering.com](info@cedengineering.com) | | [www.cedengineering.com](www.cedengineering.com) | HVAC – How to Size and Design Ducts – M06-048 HVAC HOW TO SIZE AND DESIGN DUCTS | | HVAC – How to Size and Design Ducts – M06-048 | | --- | --- | | 1.0. | CONTENTS
DUCTWORK DESIGN PRINCIPLES
1.1 Basic Definitions
1.2 Air Flow Principles
1.3 Total Pressure, Velocity Pressure, and Static Pressure
1.4 Air Flow Characteristics in Duct | | 2.0. | DUCT COMPONENTS & MATERIALS | | 3.0. | 2.1 Duct Components
2.2 Duct Materials DUCT CLASSIFICATION
3.1 Velocity Classification
3.2 Pressure classification
3.3 Velocity classification v/s Pressure classification | | 4.0. | DUCT SHAPES | | 5.0. | 4.1 Round Ducts
4.2 Rectangular Ducts
4.3 Oval Ducts
4.4 Equivalent Diameter DUCT SIZING
5.1 Equal friction method
5.2 Velocity Reduction Method
5.3 Static Regain Method | | 6.0. | PRESSURE LOSSES IN AIR DISTRIBUTION SYSTEM
6.1 Duct Friction Losses
6.2 Duct Fitting Dynamic Losses
6.3 The Concept of Duct Equivalent Length | | | i | | HVAC – How to Size and Design Ducts – M06-048 | | --- | | 6.4 Pressure Loss across Components | | 7.0. FAN SIZING | | 7.1 Fan Selection Example | | 7.2 Balancing Air | | 7.3 Fan System Effect | | 8.0. THE SUPPLY DUCT SYSTEM | | 8.1 Extended Plenum Systems | | 8.2 Reducing Plenum System | | 8.3 Reducing Trunk System | | 8.4 Spider System | | 8.5 Radial System | | 8.6 Perimeter Loop System | | 8.7 Rules of Duct Design (ACCA Manual D – Residential Duct Systems) | | 9.0. RETURN DUCT SYSTEMS | | 9.1 Distributed Return | | 9.2 Central Return | | 9.3 Pressure Balancing | | 10.0. DUCT FITTINGS AND TERMINAL UNITS | | 10.1 Duct Fittings and Transitions | | 10.2 Volume Control Dampers | | 10.3 Fire and Smoke Dampers | | 10.4 Diffusers, Grilles & Registers | | 10.5 Location of Air Inlets and Outlets | | 11.0. DUCT CONSTRUCTION & REINFORCEMENT | | 11.1 Duct Construction | | 11.2 Duct Sheet Metal Thickness | | ii | | HVAC – How to Size and Design Ducts – M06-048 | | --- | | 11.3 Aspect Ratio | | 11.4 Standard Duct Sizes | | 11.5 Duct Fabrication and Lengths | | 11.6 Duct Hanger Spacing | | 12.0. GOOD ENGINEERING PRACTICES | | 12.1 Energy Conservation | | 12.2 Good Engineering Practices for Designing Ductwork | | 13.0. DUCTWORK INSULATION AND SEALING | | 13.1 Ductwork Insulation | | 13.2 Ductwork Air Leakage | | 13.3 Duct Leakage Tests | | 13.4 Duct Sealing | | 14.0. DUCT ATTENUATION AND NOISE CONSIDERATIONS | | 14.1 HVAC Noise Points | | 14.2 Acoustical Analysis of a Ductwork System | | 15.0. DUCTWORK TESTING & SYSTEM PERFORMANCE | | 15.1 Balancing the System | | 15.2 Testing Methods and Equipment | | 15.3 Air Flow Measurement Instruments | | 15.4 Determining Air Flow at Grilles | | 15.5 Determining Air Flow in Ducts | | 15.6 Provisions during Design for Testing, Adjusting, and Balancing | | 16.0. DUCT CLEANING | | 16.1 Duct Cleaning Methods | | 16.2 Coordination between Design Specialties | | iii | HVAC – How to Size and Design Ducts – M06-048 HVAC – HOW TO SIZE AND DESIGN DUCTS Air flow problems have plagued the HVAC industry for years. No matter how much money you spend on a high-quality HVAC system, the equipment won’t work at its best without properly designed and installed ductwork. Ducts that are not well designed result in discomfort, high energy costs, bad air quality, and increased noise levels. A well-designed ductwork system should deliver maximum interior comfort at the lowest operating cost while also preserving indoor air quality. The chief requirements of an air conditioning duct system are: 1. It should convey specified rates of air flow to prescribed locations. 2. It should be economical in combined initial cost, fan operating cost and cost of building sp

FAQs

Why is properly designed ductwork important in HVAC systems?

Ductwork must be designed and installed to perform at its best. Poor design leads to discomfort, high energy costs, bad air quality, and increased noise levels.

What are the main requirements of an air conditioning duct system?

It should deliver specified air-flow rates to prescribed locations, be economical across initial cost, fan operating cost, and building space, and avoid objectionable noise transmission or generation.

How does gauge pressure relate to absolute pressure in duct design?

Gauge pressure is what the gauge indicates, while absolute pressure equals gauge pressure plus atmospheric pressure. For example, 10 psig corresponds to 24.7 psia using 10 psig + 14.7 psi = 24.7 psia.

Nov 4, 2026

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