HVAC Ductwork

Galvanized Ducts

Galvanized ducts belong to the first generation of ductwork and are manufactured and installed using traditional methods, which come with a number of drawbacks. As we know, one of the main applications of ducts is in HVAC systems for conveying conditioned air. Since conditioned air generally has a lower temperature than the ambient dew point, and given the high thermal conductivity of galvanized steel sheets, the duct surface must be fully insulated to prevent condensation of water vapor.

For insulating these ducts, materials such as rock wool or fiberglass are commonly used. However, due to the inevitable air leaks through the duct joints, airborne fibers can enter the building environment, potentially causing respiratory and skin irritation—making this one of the major disadvantages of galvanized ducts. To overcome this issue, elastomeric insulation may be used, but this significantly increases costs for the client.

Disadvantages of Galvanized Ducts:

Very heavy weight

Requires numerous supports and hangers for installation

Difficult and labor‑intensive insulation process

Low installation speed

High energy losses due to numerous joints and air leaks

Susceptibility to corrosion and relatively short service life

Pre‑Insulated Ducts

These ducts consist of a polyurethane foam core, ranging from 1 to 3 cm in thickness, sandwiched between aluminum facings on both sides. The foam provides thermal insulation, while the aluminum layers enhance structural strength, protect the insulation, and offer resistance to moisture. Pre‑insulated ducts serve as a viable alternative to traditional galvanized ducts.

Advantages of Pre‑Insulated Ducts:

Lightweight construction, reducing structural load

Requires fewer supports and hangers

Flexible and easy to adapt on‑site

High installation speed

Long‑term resistance to rot and corrosion

Low noise and vibration levels during operation

Integrated insulation and duct structure

Flexible Ducts

Flexible ducts (also known as flexible hose or spiral ducts) are primarily used in locations where space constraints prevent the installation of rigid rectangular ducts. These ducts are manufactured in various types, including thermal‑insulated (fiberglass), fabric‑reinforced, and aluminum versions. They serve as a suitable replacement for old galvanized ducts and are the preferred choice for ducted split systems. With their aluminum outer coating, they offer good resistance to tearing and impact, while their smooth inner surface helps minimize pressure losses.

Advantages of Flexible Ducts:

Ideal for use with ducted split systems

Well‑suited for humid and coastal climates

Requires fewer hangers and supports

Low noise and vibration during operation

Fast and easy installation

Reduced installation costs

Lightweight and flexible

Can be installed at various angles

Fabric Ducts

Fabric ducts are manufactured from specially engineered fibers using the latest technologies for air distribution. Due to their numerous advantages, their use is rapidly growing. They can be applied in a wide range of buildings, including warehouses, swimming pools, sports facilities, production halls, storage areas, cold rooms, restaurants, retail stores, public and office spaces, laboratories, cleanrooms, and more.

Advantages of Fabric Ducts:

Quieter operation compared to metal ducts

Lighter than metal ducts

No additional insulation required

Occupies less space than metal ductwork

Reduced manufacturing and installation time

Fire‑resistant

Resistant to bacteria and fungal growth

Provides uniform air distribution

Plastic Ducts

Plastic ducts share many of the same characteristics as fabric ducts, with the primary difference being the material composition.

Advantages of Plastic Ducts:

Lightweight

More cost‑effective than galvanized ducts

Fast installation

Low noise during operation

Reduced velocity and pressure losses

Easy to transport

Minimal waste generation

Excellent thermal insulation properties

Resistant to rot and corrosion

Types of Ducts by Cross‑Sectional Shape

Duct cross‑sections can be designed as either rectangular or round (spiral). Each type has its own set of advantages and disadvantages depending on the application.

Rectangular Ducts

Advantages of Rectangular Ducts:

No need for expensive specialized equipment

Lower cost and more economical

Quick and straightforward design

High installation speed

Disadvantages of Rectangular Ducts:

Occupies considerable space

Heavy and bulky

Dust accumulation inside due to non‑uniform airflow profile

Significant noise generation during operation

Round (Spiral) Ducts