The downside of flex ducting is that it is considered temporary with an acknowledged lifespan of only about 15 years. Another major disadvantage is that they are a little too flexible, so they are often incorrectly installed. And with greater friction than metal ducts, proper sizing is critical.
What is the main problem with flex duct?
The most common problems we see with flex ducts are: Kinks. Sharp turns. Long duct runs without proper support.
What is better flex duct vs hard duct?
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.
How long can you run flexible duct?
It says, “Length limitation: Factory-made flexible air ducts and connectors should not be more than 5 feet (1,524 mm) in length and shall not be used in lieu of rigid elbows or fittings.”
Is flex duct waterproof?
FlexClad™ is the flexible, weatherproof, economical, and easy-to-install jacketing system for pipe and duct applications. Since 1961, MFM Building Products has been a manufacturer of innovative, waterproofing membranes for the HVAC/Insulation and construction industries.
What is the benefit of flexible duct?
Flexible ducting is durable because they don’t need to be replaced soon and their use can be prolonged up to 25 years and they are made of high-quality material which makes them unbreakable while transferring material from one place to the other and invulnerable to any toxic material that can damage them because of
Is it OK to use flex duct for return air?
Flex duct is widely used for return air in commercial air conditioning systems. Flex duct is able to withstand a certain negative pressure of return air. When installed properly, a flex duct is a reliable and convenient ductwork solution.
Does Flex duct restrict air flow?
Friction is the enemy of airflow. Unlike rigid ducts, which are cut to length within a tolerance of 1 inch or less, it’s easy to cut a length of flexible duct that’s several feet longer than is needed to get from point A to point B [2A]. That creates slack in the duct, which reduces airflow for two reasons.
Can you squeeze flex duct?
When flexible ducts are installed in unconditioned areas of the home, they should not be squeezed into any cavities that are smaller than the outer diameter of the duct, including the duct insulation; in conditioned space, they should not be installed in cavities smaller than the inner duct diameter (ENERGY STAR).
Can 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.
What is the most efficient ductwork?
For instance, round duct is the more efficient shape in terms of material use, resistance to airflow, and air leakage. “The tradeoff is that round duct will not always fit in the space provided. In these cases the duct is converted to rectangular or flat-oval so that it can fit the available space.
What type of ductwork is best?
Flexible ductwork is the best type of ductwork to use in tight or awkward spaces where rigid ductwork would be too difficult to install. Because these air ducts are flexible, they can bend around fixed structures to work in almost any space.
What size duct do I need for a 12×12 room?
A 12×12 foot room will need a 4×8 inch supply duct to get an adequate CFM rate, which is about 144 CFM. However, these figures are just “rule of thumb” measurements and will differ based on various factors of your home and HVAC system.
How do I know what size flex duct I need?
Measure the length and width of the room where the flex duct will be supplying the air. Multiply the length and width together to get the square footage of the room. For example, a 10-by-10 room will be 100 square feet.
How often should flex duct be supported?
Supports should be installed at least every once 4 feet. The maximum allowable sag in flexible duct is one-half inch per foot. (Source: Calcs Plus.) Place supports at each connection between flex duct and rigid metal duct.
Are flex ducts insulated?
Flexible ductwork is lightweight, easy to install, and available as insulated or uninsulated. R-values range from R-4.2 to R-8.
What’s the difference between black and silver flex duct?
Why are there two types of jacket – Black and Silver? The jackets are vapor barriers. The vapor barrier is the outer membrane of the flexible insulated duct. For a stronger more durable vapor barrier your choice should be silver jacket as it is heavy duty, tear resistant and has a reinforced scrim.
What size duct do I need?
To calculate the required equipment size, divide the HVAC load for the entire building by 12,000. One ton equals 12,000 BTUs, so if a house or office needs 24,000 BTUs, it will take a 2-ton HVAC unit. If you get an uneven number, such as 2.33 for a 28,000 BTU load capacity, round up to a 2.5-ton unit.
