AutoCAD Duct Drawing Free Download Plugin (Duct, Elbow, & Tee)

The Engineer’s Guide to AutoCAD Duct Plugins. Full Walkthrough Video

Have you ever felt like drawing ductwork is a massive time-sink because every single segment and fitting has to be drafted manually over and over again?

That’s the exact frustration the Engpocket drafter team and I shared. Out of that struggle, we came up with a better way custom 2D Duct & Fitting Autocad Plugin. This is a free, ready-to-use HVAC LISP routine designed to streamline your workflow.

Best of all? Every duct and fitting comes equipped with flanges at every connection point.

Check out the step-by-step tutorial video below to see it in action!

Free Download: AutoCAD HVAC Plugin for Automated Ducts, Elbows, Reducers, and Tees

You can access the free plugin download links directly below.

Ductwork & Fittings Material Takeoff Calculator

We provide this calculator to estimate material requirements for duct fabrication based on surface area.

Step-by-Step Guide: Drawing Ducts and Fittings in AutoCAD with Free Plugin

Understanding Ductwork, Concepts and Material Specifications

Ducting / ductwork is the primary conduit for distributing conditioned air (cool or warm) from one point to another within an HVAC system.

Beyond temperature control, ducting or ductwork also functions as the essential pathway for exhaust air and fresh air intake.

Ducting (Ducts) can be fabricated using various materials. Below are the most common types used in the industry:

1. Galvanized Steel Sheet. This is the most used material by professional HVAC contractors for main duct lines. The thickness typically ranges from 0.4 mm to 1.2 mm, depending on the duct dimensions.

• Fabrication: Assembling ducts from Galvanized Steel Sheet is the most complex process among all types.
  
  There are numerous methods for cutting and joining (lock-forming) that require skill and special tools.
  
  
• Durability: Despite the difficulty, Galvanized Steel Sheet duct is the strongest and most durable option when fabricated correctly by a specialist.
  
  
• Note: This material MUST be wrapped with external insulation specially design for ducting like XLPE insulation or IXPE insulation.

2. PU (Polyurethane) / Pre-Insulated Panels PU duct comes in pre-manufactured sheets with a standard dimension of 1.2 meters (width) x 4 meters (length).

• Structure: It features a "sandwich" construction, where the rigid Polyurethane foam is bonded between two layers of aluminum foil (Alu - PU - Alu).
  
  
• Specs: The standard thickness is 20 mm, with a high density averaging between 50 kg/m³ to 53 kg/m³.
  
  
• Insulation: For standard applications, PU duct often does not require additional external insulation since the panel itself is thermally resistant.
  
  However, for critical facility installations, adding an extra layer of insulation is still recommended for maximum efficiency.

3. Flexible Duct As the name suggests, this duct is round, flexible, and capable of maintaining its shape even when bent around obstacles. This flexibility is made possible by a high-carbon spring steel wire helix acting as its structural skeleton.

• Application: Flexible ducts are typically used at the very end of the supply line, connecting the main duct to diffusers or grilles.
  
  
• Material Composition: The core consists of laminated Aluminum Foil + Polyester (PET), wrapped in Glasswool insulation, and finished with an outer jacket of reinforced aluminum foil.
  
  
• Advantage: Flexible ducts are pre-insulated, so no additional insulation work is needed.

Various Types of Duct Fittings and Accessories

Same as roadway networks or piping systems, ductwork installation is rarely a simple straight line. The air path often requires bends to navigate corners, branches to split airflow, or transitions to adjust for space constraints.

To support these complex installations, we use specific components known as Fittings. Below are the most common variations found in HVAC systems:

1. Duct Elbows (Bends)

Elbows are the essential fittings used to change the direction of the airflow. Often referred to as "bends" or "knees" in the field, they allow the duct run to turn corners smoothly.

• Types: The two standard types are the 90 degree elbow and the 45 degree elbow.

2. Duct Reducers (Transitions)

Reducers are used when the duct line needs to change dimensions, either narrowing (constriction) or expanding. Similar to a "bottleneck" in traffic, a reducer connects a larger duct section to a smaller one (or vice versa) to maintain proper air pressure and velocity.

• Shape: One end must be larger, while the other is smaller.

3. Duct Tees (Branches)

Tees are the primary fittings used for splitting airflow into multiple directions. As the name implies, they are shaped like the letter "T" and feature three openings to make branching ducts.

Common Tee Variations:

A. Standard 90° Tee: Shaped exactly like a capital "T". In this standard version, all three openings have the same dimensions.


B. 45° Tee (Lateral / Wye): Often called a "Y-branch" or "Lateral Tee" because it resembles a lowercase "y". This fitting supports angled branching for smoother airflow. All openings typically have equal dimensions.


C. 90° Reducing Tee: Similar in shape to the standard 90° tee, but the opening sizes vary. This is used when the branch line is smaller than the main line, combining branching and reduction in one fitting.


D. 45° Reducing Tee (Reducing Lateral): Shaped like the 45° lateral tee, but with varying opening sizes. It handles both angled branching and size reduction simultaneously to optimize airflow distribution.