Flexible Ducts can be one of the most efficient types of ducting systems, with relatively lower installation costs, because: They can be installed, commonly, without considerable planning and installation constraints.
While it's clear that sheet metal ducts may be the most energy-efficient ductwork due to the lower chance of damage and deterioration, each home has unique needs when it comes to its HVAC setup. Some homes may not be able to accommodate the space needed for sheet metal ducts, for example, due to tight spaces or bends.
The most efficient ductwork shape is round. A round air duct has the least surface area for air to come into contact with, which means less friction and better airflow. Square and oval are used when ductwork has to fit into a specific space.
Rigid ducting offers the best airflow, but is more expensive and harder to install. Flexible ducting is much less expensive and can be bought pre-insulated, but the flexible ridges really eat into your airflow.
Rigid ducting offers the best airflow, but is more expensive and harder to install. Flexible ducting is much less expensive and can be bought pre-insulated, but the flexible ridges really eat into your airflow.
Disadvantages of Flex Duct
Flexible ducts are more prone to air leakage around the seams, which can lead to lower HVAC system performance. Additionally, the pliable nature of flex duct tends to make them prone to tangling or crushing when they pass through tight spaces or fixtures.
Understanding the three types of ducting – flexible, rigid, and semi-rigid – is essential when selecting the appropriate ducting for your residential HVAC system. Factors such as space requirements, system pressure, indoor air quality, energy efficiency, and maintenance should guide your decision-making process.
Sheet metal, especially when insulated, is often considered the "gold standard" type of ductwork. Usually made from aluminum or galvanized steel, sheet metal ducts are available in rectangular or tubal shapes. They're sturdy and smooth, allowing for the free flow of air through them.
Properly installed and well-maintained sheet metal, PVC, or insulated ducts can last 20 to 30 years, while flexible ducts have a shorter lifespan of 10 to 15 years.
Rigid duct is considered as the best since it is more durable and less resistive than flexible duct.
The air now has to re-pressurize to regain its turbulent flow so it can continue to push its way down the duct. It requires about 24′ or two feet to do this. This is the 'Two-Foot Rule?. Ideally, you should allow at least 24′ between takeoffs and at the end of any duct run.
Sheet metal ducts
It is the most common kind of air duct and normally they are made of galvanized steel or aluminum. One advantage of the latter is its lightweight compared to other air ducts materials.
In practice, the cost of round ducting systems is usually much lower and cost effective than rectangular systems by approximately 67%.
Round ducting is often regarded as the most efficient type of ducting due to its design, which offers a larger free area for airflow compared to flat ducting. This characteristic reduces air resistance and enhances overall performance, making it an excellent choice for high-capacity HVAC systems.
Ductwork insulation also provides additional benefits, including: Moisture control – Duct wrap reduces the difference in air temperature inside and outside the ductwork, thereby mitigating condensation. Homes in humid climates may still need to use a home dehumidifier to eliminate moisture buildup on ductwork.
Since the size of your ductwork can increase or lower this measurement, you'll have to find the necessary CFM for each room before you can get the right duct size for each space. Cubic Feet Per Minute = (HVAC Unit Tons x 400) / total square footage of home. Calculate for each individual room.
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. That creates slack in the duct, which reduces airflow for two reasons.
❖ The length of flexible air ducts is not limited, unlike flexible air connectors, which are limited to 14 feet (4267 mm) (see commentary, Section 603.6. 2.1).
Over time, dust and debris can build up in the ducts, affecting the efficiency of your system. While you may be familiar with cleaning rigid ducts, you may wonder if flexible air ducts can be cleaned. The answer is yes, but to avoid damaging the ducts, you should hire a pro to clean them.
If you have mice or other rodents in the home, they will often chew through electrical wiring. Rodents can also chew through flexible ductwork and duct insulation, and they are also prone to nesting in the duct insulation or inside of the air ducts themselves.
Replacing ductwork in a crawl space costs between $2,600 to $7,300 for difficult installations with limited access. Most homeowners spend an average of $4,800. Expect to pay between $30 and $60 per linear foot of duct for the project. Get quotes from up to 3 pros!
Flexible ducts are the cheapest option and the easiest to install. However, they are also prone to sagging and kinking, which can interfere with airflow and make the HVAC system much less effective and less energy efficient.
The maximum length of flexible ducts in the UK is, 1500 mm. This is specifically regarding installing a flexible duct, which should only be used as the 'final connection'. In terms of purchase, the ducting we sell can be bought for up to 10 meters of length, depending on the ducting you buy.
Unfaced duct board, poorly fabricated joints between duct sections of any materials, and areas of low pressure found with abrupt increase or decrease in size will collect more dirt than smooth well-fabricated ducts. This dust and dirt provides the food source for mold growth when combined with water.
Less Durability and Strength: Plastic ducting is generally not as durable or strong as aluminum. It may be more prone to damage from mechanical stress or pressure. Limited Temperature Range: Plastic ducting has limitations in terms of the temperature range it can handle.