4 Benefits of Using Flexible Ductwork in Your Attic

How long has it been since you braved a glance into your attic? 

If you’ve recently noticed reduced air quality in your home or your energy bill is through the roof, your ducts might just be the culprit. While poor air quality might indicate that your ducts may need a good cleaning, poor energy efficiency and long run times for your HVAC system could be a sign that your ducts are leaking or damaged. 

If any of your vents have to be replaced, you have two options: flexible ductwork or rigid metal ductwork. In this article, we’ll explore why insulated flexible ductwork might be the right material for your ductwork repairs, in addition to Insulation removal you may need as well. 

Ductwork Explained

If you can’t tell the difference between a register and a return, don’t worry. We’ll start by covering some HVAC basics. 

Understanding your HVAC system—of which your ductwork is an integral piece—is pretty simple. 

Your HVAC system’s job is to heat or cool air and circulate it throughout your home. While all of these steps are happening simultaneously, here’s a quick rundown of how your HVAC system turns tepid air into cozy heat or refreshing air conditioning:1

  1. Most modern homes have a central air conditioner combined with a forced-air heater. When you set your thermostat to your desired temperature, either the heater or the air conditioner begins working to heat or cool air located in the plenum box, the heart of your HVAC system.
  2. A fan inside the plenum box forces the heated or cooled air through one or more trunk lines, which are essentially the major arteries of your HVAC system.
  3. Additional ducts branch off from the trunk lines, pushing air into individual rooms through registers—also called air vents. The heated or cooled air leaving the registers raises or lowers the overall temperature of the room.
  4. The air forced into an individual room through a register eventually circulates towards the return, a large vent that sucks air from the inside of your home. Air sucked into a return passes through an air filter and moves back to the plenum box via a return duct, the major vein of your HVAC system. This air is once again heated or cooled in the plenum box, and the process begins again.

So, your ductwork contains three major elements:

  • The trunk line(s)
  • Ducts branching from the trunk line to supply air through registers
  • The return duct(s)

If one or more of these components is leaking, dirty, or damaged, your HVAC system won’t function properly, and the malfunctioning component may need to be replaced. A ductwork expert will recommend two material options: flexible ductwork or rigid metal ductwork.

Why Choose Flexible Ductwork Over Rigid Metal?

There are some crucial differences between the two products, but the benefits of flexible ductwork might sway you towards installing it in your home. 

Next, we’ll explore flexible ductwork’s four major benefits. 

#1 Efficiency

The key to optimal HVAC system efficiency is leak-free ductwork. 

During installation, ductwork professionals must seal connections between ducts to prevent leaks, which can cause lower efficiency and higher energy bills. 

Ductwork professionals use two supplies for sealing—foil tape and mastic. These materials are usually used in tandem to create the strongest possible seal. Mastic, like spackle, is pliable when wet and dries into a hard coating. 

Flexible ductwork doesn’t require any sealant in its raw form, putting it at a significant advantage in terms of leak vulnerability. In addition, flexible ducts are already insulated, and the insulation layer is pre-sealed or seamless, further reducing its leak potential.2

Flexible ducts have three major components:

  • A thin metal coil that creates the tube-shaped structure
  • A layer of plastic encasing the coil
  • An outermost layer of foil-backed fiberglass insulation

Rigid metal ducts, on the other hand, consist of only one component—a rigid, thin sheet of metal. These ducts come in rectangular pieces of sheet metal, and ductwork professionals must form the sheets into a tube shape and seal the seam. 

The sealed seam in rigid metal ducts makes them much more liable to leak than their counterpart, which is pre-sealed. 

Inefficient insulation coverage around rigid metal ducts can also reduce an HVAC system’s efficiency. Insulating ducts is critical to preventing conductive heat loss in the winter and keeping conductive heat away from cool ducts in the summer. 

While flexible ducts are pre-insulated, rigid metal ducts must be insulated by hand, introducing another opportunity for operator error. If the ducts aren’t thoroughly wrapped in batt insulation, the HVAC system will have to work harder to overcome ducts that aren’t at the optimal temperature.

#2 Flexibility

From a leak standpoint, another major boon to flexible ductwork is its flexibility (just as its name suggests).

This key difference between flexible and rigid metal ductwork may seem obvious, but flexibility is an important component in the choice between the two materials. 

  • Rigid metal ductwork must run in straight lines. If the trunk line or a branching duct must curve, two straight ducts are joined by an elbow joint, which is sealed with foil tape and mastic.
  • Sealing is crucial to leak prevention and successful duct installation, and any surface or connection that requires sealant is liable to leak. Since rigid metal ducts require an elbow joint to curve around obstructions in walls and attics, they’re more susceptible to potential leakage
  • While rigid metal ducts must incorporate bent elbow joints and additional sealant to accommodate obstructions, flexible ductwork can simply bend in another direction. Unless two duct pieces are meeting at a point in the bend, there’s no foil tape, mastic, or extra joints required. Flexibility reduces the need for extra sealant, which decreases leaking risks and ensures optimal efficiency.

However, this flexibility comes with a caveat—restricted airflow.

When flexible ducts bend around an obstruction, the tube molds around the wooden joists, studs, or trusses that surround it. When the ducts bend, the tube slightly compresses, which can restrict airflow inside the duct, leading to suboptimal blowing force when the air leaves the register. 

Elbow joints are the same diameter as the rigid metal ducts they’re connecting, maintaining consistent airflow throughout the length of the vent. 

While compression and potential airflow restriction are two potential drawbacks of flexible ductwork, a trained professional will take steps to maintain consistent airflow during bending, ensuring optimal efficiency. 

#3 Cost

Flexible ductwork and rigid metal ducts often carry different price tags. Flexible ducts are typically cheaper to install because:

  • They require less foil tape and mastic since they feature lower sealant requirements in general
  • They’re already insulated, shaving significant time from the installation process and reducing the labor cost
  • They bend easily, requiring less installation time than is needed to create a bend in rigid metal ductwork

As the prices of building materials continue to climb, materials costs alone can make a significant dent in your duct repair or replacement budget.3

Especially if you’re performing ductwork in tandem with another efficiency-improving measure in your home—like insulation installing or insulation removal—cost is likely very high on your priority list for home improvement. If you’re seeking  attic services for HOAs, there may be cost benefits or group discounts for services like flexible ductwork installation. 

If a ductwork professional determines that your duct replacement won’t require significant bends due to current register and return placement or lack of obstructions, a quote for rigid metal ductwork might be more comparable to its flexible counterpart. However, you should be wary of professionals who provide a labor quote without thoroughly examining your attic or the floor trusses between stories (to the extent that they can). 

#4 Ease of Installation

There are two major factors ductwork experts consider to estimate labor costs—obstructions in the installation area and materials used.

Some common obstructions in attics and floor joists include:

  • Structural steel beams, which are typically wider than wooden studs
  • Receptacles for electrical outlets, can lights, or switches
  • Other HVAC equipment, like air handlers in the attic

In an installation area with numerous obstructions, the choice of duct material can make or break labor costs. Installing elbow joints takes more time than simply bending a flexible duct around a can light. In general, installing flexible ductwork is easier and less time-consuming than rigid metal ductwork. 

Unlike insulated flexible ductwork, rigid metal ducts aren’t pre-insulated. Insulation Installation  requires professionals to ensure that the metal seam is completely sealed, wrap it with batt insulation, and seal yet another seam with foil tape. This process takes significantly more time than placing and sealing pre-insulated ducts. If you’re looking to take the DIY route when working in your attic, make sure you’re treading safely by educating yourself on the electrical hazards in your attic.

Opting for an easy- and quick-to-install material will lead to reduced installation times and labor cost savings.

Give Your Ductwork a Facelift with Attic Construction

While rigid metal ducts certainly have a place in residential HVAC technology, flexible ductwork shines as an efficient, flexible, affordable, easy-to-install alternative. 

But, if you’re still on the fence about which duct material to use in your replacement project, or if you’re not even sure if your ducts need to be replaced, give our expert team a call. We can talk you through the process of cleaning, repairing, or replacing your ducts, and we’ll take a peek at your HVAC equipment as a part of our free consultation. If you’re already planning on having attic insulation construction take place in your home, it’s important to know how to prepare your attic for insulation

Attic Construction has been improving energy efficiency for over a decade, and we have the tools to help you reduce your energy consumption at home. Schedule a free consultation with our expert team today.


  1. Trane. How Does Central Heating and Cooling Work? https://www.trane.com/residential/en/resources/hvac-basics/how-does-a-central-heating-cooling-system-work/ 
  2. Office of Energy Efficiency and Renewable Energy. Sealed and Insulated Flex Ducts. https://basc.pnnl.gov/resource-guides/sealed-and-insulated-flex-ducts 
  3. National Association of Home Builders. Building Material Prices Climbing at Record Year-to-Date Pace. https://nahbnow.com/2021/08/building-material-prices-climbing-at-record-year-to-date-pace/ 

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