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Fiberglass Duct Board vs Sheet Metal: Who Beats Who?

Selecting the best material for your HVAC unit is quite crucial. Because a wrong decision might require you to remove the whole unit. 

Most people end up confused with the last two possible options: fiberglass duct board vs sheet metal. Without a proper head-to-head comparison, it’s quite tough to declare the best one.

Sheet metal is quite durable and the most ideal choice for longevity. On the other hand, fiberglass duct boards outnumber sheet metal in terms of advantages. Like they are lightweight, highly insulated, and more. However, sheet metal covers the areas in need of attention and manages to be the most reliable one.

To figure out the better one for you, this guide has provided a detailed comparison. So let’s move on:

Fiberglass Duct Board vs Sheet Metal: Comparing the Features


Fiberglass Duct Board

Sheet Metal



Easier Installation Process


Better Insulation


Noise Reduction Ability


Simple Repairing Procedure


Longer Shelf-Life 


Fiberglass duct board and sheet metal are the top-notch HVAC materials in the market.

Honestly, you can select the best material when you are well aware of what you want out of your HVAC unit. Because certain people have different expectations. 

We’ve sorted the advantages you should get from both of the materials. This will allow you to choose your preferred one according to your expectations.  


Using energy-efficient ductwork is, without a doubt, a blessing in the longer run. Because everyone hates massive electricity bills at the end of the month.

Metal sheet ones are made up of galvanized steel or aluminum. Even you can get them ready in rectangular or round shapes.

There’s a myth about metal sheets being less efficient. However, a perfect installation might be more efficient than the fiberglass duct board.

A well-done sheet metal HVAC unit keeps the consistency of airflow. Thus, prevents condensation from happening. 

In the future, you don’t have to worry about the tightness of metal. With mastic, metal is pretty tight. You can even apply some paint to this. 

Fiberglass duct board is usually a contractor’s second option. Even though it’s made from durable fiberglass sheets, it does have some drawbacks.

The fibrous material can erode easily in the airstream. It affects the efficiency of the whole unit in the future. Since the fiberglass loosens up, it takes more energy for the HVAC to pass air. 

Installation Process

When installing sheet metal, you’ve to make sure that the space is unconditioned. 

To ensure the effectiveness of the installation, the wrap around the duct shouldn’t be pulled too tight or too loose. 

The installation is cheaper for sheet metal. Because the tools needed are quite popular and cheaper. Also, most professionals are more used to installing sheet metal.

Here are some of our favorite tools used for sheet metal duct installation:

Our Recommended Product


The installation process of fiberglass duct board is messier than sheet metal. Moreover, installation tools are costly and rare in the market. 

The fiberglass air ducts must be properly sealed. So that the place of installation must be safe from moisture. 

If you’re planning on installing ducts in a damp area, better get the sheet metal. Moisture won’t be an issue for that material. 

Better Insulation?

Among the two, fiberglass ducts are way better insulated. 

Sheet metal, however, can be insulated from inside or outside of the duct. But insulating a sheet metal duct is a costly and time-consuming process. 

Insulating in the basement or closed spaces like that is a real challenge. Often, fiberglass helps the sheet metal to insulate in these areas. 

Fiberglass duct boards already come as insulated. It doesn’t need any extra hand to heatproof your HVAC unit. 

Noise Reduction Ability

Constant irritating noise from the HVAC unit should be a major concern. The less noise, the better. 

The core material of metal sheet ducts is aluminum and steel. Airflow creates a vibration on the metal surface and it starts to get noisy. 

The rigid fiber of a fiberglass duct board cancels out noises. Noise can’t transfer from one place to the other through such material. So it has an excellent noise reduction capability. 

Well, you can reduce the sound of the noisy air duct. But you can’t get rid of it. 

Repairing Procedure

Time starts to affect the HVAC units no matter what the material is. As days pass away, repairing becomes regular for both types of air ducts. 

Often few adjustments like adding a vent or cutting ductwork are considered as repairs too. 

Repairing sheet metal air ducts can be easier in this case. You can easily use tapes or mastics for tears or easy fixes. Even the most critical fixes are easier to deal with. 

If you need to repair a fiberglass duct board, it can be a hassle. As it’s made of fiber material, it cannot be easily fixed. It needs expensive tools and professional help as well.


The longevity of a material plays a huge role in an HVAC unit. The longer it lasts, the better it is for your house.

Sheet metal ducts are one of the most durable constructions out there. So if you’re searching for material with longevity, choose sheet metal ducting. 

This ductwork can survive about 10 years without failing. Generally, a quality HVAC unit lasts for at least 10 years. So, you won’t have to change your ducting frequently.

Fiberglass duct boards can last longer if it’s safe from moisture. You can’t use a fiberglass board in damp areas and expect it to last. 

Moisture or dampness allows mold and bacteria to build up. Moreover, it harms the material itself.

Additional Tips 

The wisest decision, in this case, is to consult a professional. They’ll suggest the best solution for your house after inspecting it. 

If you’re planning to do the installation on your own, please start with the proper gears. The tools and the materials both can be a concern for your safety. 

Use masks, gloves, and goggles especially if you’re dealing with fiberglass. It might even cause a life threat. 


Question: Is fiberglass duct board safe?
Answer: Fiberglass duct board has the ability to cause cancer among animals. This is ensured by the Environmental Protection Agency (EPA). Fiberglass ducts can also be an ideal place for mold and bacteria to grow.

Question: Is round or square duct better?
Answer: Round ducts can be considered better than square ducts in terms of efficiency. However, the round duct barely keeps any exposed space of the duct wall. Moreover, you will be saving 32% of the metal used in a square duct. Reduced metal, reduced costing.

Question: How often should ductwork be replaced?
Answer: 10-15 years is the average lifespan of the ductwork in your home. Generally, no issues appear till this time. If your ducts are older than that, check them right away. 


There goes all the information among the two best materials for the ducts. Hopefully this comparison between fiberglass duct board vs sheet metal helped you.

A piece of advice, avoid the carcinogen fiberglass if you’re a health concerned person. Sheet metal might not have many advantages, but it’s not threatening your health.