Asked by: Edesio Moar
home and garden indoor environmental quality

What is flexible duct for HVAC?

Last Updated: 7th June, 2020

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Flexible or flex duct is an integral part of an air conditioning system. The flexible ducting connects the heating and cooling system ductwork to the air distribution. Flex duct is convenient for attaching supply air outlets to more rigid ductwork made from sheet metal.

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Subsequently, one may also ask, what is flexible air duct?

On most projects, HVAC ductwork is located in designated chases that maximize the efficiency of the airflow. Flexible ducts can speed installation by reducing the number of joints in a run and eliminating the need for elbows and offsets. They also easily conform to oval as well as round connectors.

how much does flexible ductwork cost? Typical costs: Replacing aging, leaking or inadequate ductwork typically costs about $35-$55 a linear foot for labor and materials, or $1,000-$5,000 or more for a single-family home, depending on the length and type of ducts used (sheet metal, fiberduct or round flexible ductwork) and local rates.

Accordingly, how long does flexible ductwork last?

Metal ductwork has a great life as long as no moisture or water has gotten in it and can last for a hundred years or more. Flex duct shelf life can vary greatly depending on the type of ductwork installed. Silver lining ductwork can last more than 50 years.

How do you install flexible HVAC ductwork?

How to Install Insulated Flex Duct

  1. Measure the distance between the plenums or collars where the flexible duct installs.
  2. Roll back the plastic or foil jacket and the fiberglass lining approximately 8 to 12 inches from the inner core.
  3. Spread a thin layer of mastic glue onto the beaded end of the plenum or metal collar.

Related Question Answers

Lier Dalberg

Professional

Is flexible ductwork good?

Flexibility. Flex ducts are better for existing trunk-and-branch heating and cooling systems. This is because they're more versatile and flexible. Metal ducts are more rigid due to the nature of steel, making them ideal to build an entire HVAC system.

Stefanka Enecoena

Professional

Should I replace metal duct with flexible?

Metal duct can still be found in many older homes, but flexible duct is more prevalent in newer homes. Both work well. Still, should you decide to change from metal to flexible duct, don't waste money on an HVAC contractor. It's a time-consuming job, but definitely one you can do yourself.

Lucinio Chenrim

Explainer

Does Flex duct reduce airflow?

Too often, flex ducts are not installed properly, and they end up kinked, bunched up, undersized, or sagging. These issues can cause increased resistance in the duct system, resulting in too little airflow reaching a building's heating and cooling equipment.

Maisaa Caso

Explainer

What is the max recommended length of flexible duct?

Flexible air connectors which are listed to UL 181 are allowed by the standard in lengths up to 14 feet. This product is specifically evaluated for the maximum length up to 14 feet, and the manufacturer's installation instructions are reviewed to ensure proper installation up to this length.

Ihab Bakunovets

Pundit

Can you use flex duct return air?

Re: Flex Duct on Return Air Diffusers - Yes or No? Flex duct effectively creates a tight radius elbow where it turns into the top of a diffuser. The high pressure loss is further increased because the flex fabric gathers at the inside of the throat and reduces the effective diameter.

Shushanik Minayo

Pundit

Can you cut Flexible ducting?

Installation Tips & Tricks — To cut flexible duct, use a steak knife from your kitchen drawer to cut through the outside jacket, fiberglass insulation and inner plastic core. Then cut the wire with a pair of wire cutters.

Erma Renilla

Pundit

Can flexible ductwork be cleaned?

A duct cleaner/installer says: flex duct can't be cleaned properly — must be replaced. A cleaner installer says: flex duct can be cleaned. He uses a vacuum truck and some agitators to dislodge debris. He also comments that rotary brushes can't be used in flex duct because they'll tear it up.

Davina Doppelgatz

Pundit

Is it bad to close vents in unused rooms?

Despite that logic, it's actually a common misconception that closing vents in unused rooms saves energy. In fact, it can actually waste more energy than operating your system normally does. The added pressure from closing a vent can cause air leaks in your system, causing long-term and unnecessary energy waste.

Gagandeep Mardin

Pundit

Can I replace ductwork myself?

Yes, having punctures in your ductwork due to pests is something that necessitates getting those ducts replaced, or at least repaired, and, yes, it is also a really tough job for you to take on yourself.

Circuncision Gadde

Teacher

When should HVAC ducts be replaced?

“If your ductwork is over 15 years old, you probably should replace it. Ductwork has a maximum lifespan of 20-25 years. By 15 years, however, it begins to deteriorate, significantly reducing your HVAC system's efficiency, so replacement is the prudent option.”

Jassim Cancelinha

Teacher

Is it worth it to have your ducts cleaned?

If no one in your household suffers from allergies or unexplained symptoms or illnesses and if, after a visual inspection of the inside of the ducts, you see no indication that your air ducts are contaminated with large deposits of dust or mold (no musty odor or visible mold growth), having your air ducts cleaned is

Taieb Gonilho

Teacher

How much does it cost to run new ductwork?

The average home will need 30-90 linear feet of ductwork at an average cost of $35-$55 per foot. That brings your average cost between $1,000 and $5,000 based on a full-home installation.

Shavon Marklein

Teacher

How do you know if you need new ductwork?

Some of the most common signs you should replace your ductwork are old ducts, high utility bills, and poor indoor air quality.
  1. Old Ductwork. The ductwork in most homes lasts between 10 and 15 years before problems arise.
  2. High Utility Bills.
  3. Poor Indoor Air Quality.

Mykyta Hochard

Reviewer

How do you increase airflow in ductwork?

3 Simple Ways to Improve Your Furnace's Airflow for More Comfort
  1. Unblock and clean your vents. Here's a super easy way to increase air flow.
  2. Change your filters and clean your return grill. A dirty air filter impedes air movement and makes it hard for your furnace to work efficiently.
  3. Seal leaky ductwork. Snap on some goggles and a dust mask, it's time to check out your air ducts.

Hmida Eulenhaupt

Reviewer

How do you seal HVAC ducts?

Duct joints should always be secured with #8 sheet-metal screws before seams are sealed with mastic. Sealing duct seams is messy work, so wear old clothes. The mastic is spread over duct seams with a disposable paintbrush, putty knife, or your fingers. (If you spread mastic with your fingers, wear rubber gloves.)

Baghdad Tilstra

Reviewer

Is exposed ductwork cheaper?

Even when ductwork is exposed, it's anything but unfinished. Hidden ductwork is typically blocky, dirty, oily and generally not aesthetically pleasing. Round or oval ducts deliver a more “finished” look but are significantly more expensive.

Aihong Karle

Reviewer

What is the best material for ductwork?

Galvanized steel and aluminum are the most common materials for sheet metal ducts. Aluminum in particular is relatively light and easy to install. They are also the least likely to harbor dangerous molds or growths because they have non-porous surfaces.

Sharonda Irunbarrena

Supporter

What are the different types of ductwork?

There are three main types of rigid ductwork: sheet metal ducts, fiberglass lined ducts, and fiberboard ducts. Sheet Metal Ducts: Sheet metal ducts are usually made of either galvanized steel or aluminum.

Georgia Mikhoels

Supporter

Should HVAC ducts be insulated?

Proper insulation will ensure that the regulated temperature will be maintained as the air makes its way from the furnace or air conditioner to your living areas. The ductwork in unconditioned areas, such as basements, floors, and ceilings is where ductwork insulation is most necessary.