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  • Rectangular Duct
  • Rectangular Duct
  • Rectangular Duct

Rectangular Duct

  • Different kinds of Rectangular Ducts for choosing
  • Complete sets of Rectangular Duct fittings available
  • Professional installing team available for big projects

Biyang Rectangular Duct, also named HVAC Rectangular Duct, Square Vent Duct or Square Air Duct, is a kind of Rectangular Sheet Metal Duct.  It is made through by metal sheet cutting, bending, and welding.  The type of metal used for ductwork mainly includes galvanized steel, stainless steel 201, or stainless 304.

As a result, it can be divided into Rectangular Galvanised Ducting and Stainless Steel Rectangular Ductwork as well.  Based on different rust resistant standards and surface treatments, you can always select the right Rectangular Duct to fit your own environment requirement from Biyang.

Compared with Spiral Duct, Biyang Rectangular Duct is more old-style and easily manufactured duct, still widely used both home and abroad.  The setting up for square one is easy, but it requires lots of fittings and accessories as well.

Biyang provides a complete set of duct fittings for our Rectangular Ductwork, including Flat Flanges, Corners, Duct Connector, Duct Transition, Duct Boot, Duct Splitter and so on.  You can always get a one-stop solution for Square Ductwork here in Biyang.

Biyang Insulated Rectangular Duct is a duct with an insulation layer, whether glass fiber or rubber foam. The insulation material helps save energy and maintain long term efficiency. Biyang Double Wall Rectangular Duct includes outside duct and inner duct, with an insulation layer between them.

This design ensures the longer life expectancy for the insulation and is a great choice for the tough environment.  Unlike Flexible Ducts, one disadvantage of a Rectangular Duct is that it is big in volume so it is space taking for container loading.  Lots of space will be wasted.

Biyang can provide half section of Rectangular Duct, L shape, in our production and shipping.  After receiving, you can only do welding work at a site, or you can ask Biyang workers to come to your site and do the welding work if welding work is too expensive in your own country.

Biyang has several working team dealing with big oversea projects.  Biyang also provides L shape as the main trunk of ducting.  You can snap two pieces into a Rectangular Duct trunk easily without complicated tools.

Please make sure you can seal it with the ducting sealant or duct tape to be more efficient and energy saving.  For some projects, this will greatly reduce the overall budget.

Contact Biyang to get directions or quotes for your Rectangular Duct now.

ProductRectangular Duct
MaterialStainless steel, Galvanized steel

Rectangular Duct: The Ultimate FAQ Guide

1. What is Rectangular Duct?

Rectangular ducts are types of rectangular sheet metal ducts that supply air for ventilation purposes in diverse applications.

 Rectangular duct

Rectangular duct

2. What are the Advantages of Rectangular Duct Cross-section?

The advantages that you will experience by using the rectangular duct cross-section include:

  • You can adapt the rectangular duct cross-section to any building height restriction.
  • You can easily ship it in a truck after nesting or breaking it down.
  • You can fabricate it conveniently to provide a flat surface for branch tap-ins in a branch and trunk design.

3. Are there Double Wall Rectangular Ducts?

Yes, there are double wall rectangular ducts.

Double wall rectangular ducts feature the inner and outside duct including an insulation layer in between.

4. How do you Specify Rectangular Duct?

You will specify a rectangular duct through the following features:

  • Material of the rectangular duct which can either be galvanized steel or stainless steel.
  • Dimensions in terms of thickness and size of the rectangular duct.
  • Type of insulation layer which can be rubber form or glass fiber.

 Rectangular duct system

 Rectangular duct system

5. What are the Drawbacks of Rectangular Duct for HVAC Systems?

The main drawbacks that you will experience while using the rectangular duct include:

  • It is big in size and requires a lot of installation space.
  • Rectangular ducts also tend to leak at the joints thus reducing the efficiency and reliability
  • The methods of cleaning rectangular ducts are difficult and costs more.
  • It has large surface areas thus creating more friction leading to high energy loss.
  • It also has uneven pressure gaps throughout the system meaning higher costs and lower efficiency.

6. Is there Size Limitations for Rectangular Duct?

No, there is no size limitation for rectangular ducts.

You will settle on a size that will fit your application needs appropriately.

7. Where can you use Rectangular Duct?

You can use a rectangular duct in the following areas:

  • Large buildings to provide proper ventilation
  • Kitchen areas to allow for proper ventilation by sucking away unwanted smoke
  • Industrial applications where it brings in fresh air and eliminates the foul air

8. Rectangular Duct are made from which Material?

Rectangular ducts are made from different materials such as:

  • Galvanized steel
  • Stainless steel 201
  • Stainless steel 304

9. What Accessories do you need alongside Rectangular Duct Systems?

When installing a rectangular duct, you will need the following accessories:


  • Flat flanges
  • Corners
  • Duct connectors
  • Duct transition
  • Duct splitter
  • Duct boot

10. Why use Insulated Rectangular Duct?

You should use insulated rectangular ducts because the insulation helps in saving energy and increases long term efficiency.

11. How do you Size Rectangular Duct System?

You can size rectangular duct systems by going through the following steps:

  • Figure out the number of BTU’s that your furnace produces then divide the number you get by 10,000 BTU’s.
  • Multiply the number by the cubic feet of airflow produced by the furnace in a minute then divide it by 10.
  • After that, you will calculate the size of the duct vents by multiplying the length and the width.
  • Divide the CMF in every vent by the number of CMF of your furnace before finding the square footage of the room.
  • Divide the number of vents by the square footage of the room to determine the size of rectangular duct.

12. What is Rectangular Duct Offset Transition?

Rectangular duct offset transition is the process of changing the shape or size of the duct work.

You can use the rectangular duct offset transition to avoid obstacles and other mechanical services.

13. Why Buy Biyang Rectangular Duct System?

 Rectangular duct system

Rectangular duct system

You should consider buying rectangular duct systems because of the following reasons:

  • The material is corrosion resistant thus increasing the safety and durability of the rectangular duct system.
  • The rectangular duct system comes with insulation layers with different insulation materials.
  • Biyang provides complete duct fittings for the rectangular duct systems.
  • It has special designs that guarantees longer life expectancy for the insulation materials.
  • Biyang can supply the rectangular duct in sections that are easy to assemble through welding of parts.

14. What is Trunk Duct

Trunk duct is the complete cross-section of a rectangular duct that does not require any form of fabrication before installation.

You can easily use two L shapes rectangular ducts into a trunk duct without using complicated tools.

15. What is Duct Reducer?

This a type of ducting fitting that you can use to change the size of the rectangular duct.

It is capable of maintaining maximum flow of air through the system as you change the size of the duct.

16. How does Rectangle Duct and Square Vent Duct Compare?

Square vent duct has equal dimensions in terms of the length and width thus covering less space and conserving more energy.

Rectangular vent ducts have longer lengths in comparison to width thus increasing surface area and wasting more energy.

Both rectangular and square vent ducts are prompt to frequent leakages due to the sharp joints at the edges.

17. Why are Air Ducts Rectangular?

Rectangular ducts are often more important especially when you have tight spaces prompting height restrictions for round ducts.

It also increases the aesthetic value of the connections between the main duct and fan coil.

Rectangular air ducts are also easy to fabricate in comparison to other shapes of ducts.

18. How does Spiral Duct and Rectangular Ducts Compare?

You can compare the spiral duct and rectangular duct in terms of the following:

Rectangular duct vs spiral duct

Rectangular duct vs. spiral duct

· Leaks

Spiral ducts often leak less in comparison to the rectangular duct as it lacks longitudinal joints and have few transverse joints.

· Noise Level

Spiral ducts have better and lower pressure drop characteristics and is more rigid than rectangular ducts.

This reduces the fan speed and produces very little noise in comparison to that of a rectangular duct.

·  Insulation Properties

Spiral ducts are stiffer and easier to insulate in comparison to the rectangular ducts.

The outside insulation of the spiral duct work is more difficult and expensive.

19. What are Galvanized Rectangular Duct?

Galvanized rectangular duct is a type of rectangular duct with a galvanized surface finish.

The galvanized surface finish enables it to improve the corrosion abilities thus increasing the life span of the rectangular duct.

20. What is L Profile Rectangular Duct?

L profile rectangular duct is the half cross-section of a rectangular duct when it is separated diagonally.

It becomes easier to transport the L profile rectangular duct and assemble at site.

21. Is Round Duct better than Rectangular Ductwork?

Yes, round duct work is more efficient in comparison to rectangular ductwork in performing the same functions.

It has a smaller cross-sectional area and less duct wall exposure to moving air thus saving more energy.

22. Which Standards for Rectangular Ducts should you look for?

You should look for certain rectangular duct standards such as:

  • Resistance to corrosion standards
  • Tensile strength standards
  • Weight of the rectangular duct standards
  • Quality of the material standards.

All these standards are dictated under the quality standards manual such as ISO and cGMP quality standards.

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