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The basic goal of any duct system is to provide an even temperature distribution throughout the house without any noticeable amount of stratification or noise. The size and design of the ductwork is just as important as the selection of the main components of the heating system, because, when it comes to airflow, the laws of physics apply; air follows the line of least resistance. Poorly designed ductwork can seriously curtail proper system performance. These factors usually show up in uneven temperatures through out the conditioned area. If a duct system is properly designed and installed, you can expect to have less infiltration of unprocessed air, because with a properly installed duct system, you will have less duct leaks. Duct leaks result in conditioned air loss, which in turn is replaced by unfiltered and unprocessed attic air. It brings in humidity and dirt and contaminates the air you breath. In many situations where ductwork has been installed improperly, leaking ductwork can account for 10-25 percent of total heating and cooling costs. This is because the system becomes less efficient if cooled air is allowed to escape into unconditioned spaces. When installing ductwork it is important to take into consideration the type of home you have along with the three major types of ductwork: Flex, Hard Pipe and Hybrid.

Flexible Ductwork

A flexible duct system consists of insulated, plastic duct runs, which are supported by a wire wall ribbing. Flex ductwork can be a death sentence to almost any air conditioning system, if not designed and installed correctly. The basic product design problem is the inherent airflow design deficiency that is built in, namely the wire wall ribbing. The air flow encounters restriction when it travels against the wall ribbing, and when the ductwork installation is poor with problems such as kinks, insufficient diameters, no sub-plenums, and excessive lengths, the overall performance suffers because the system works much harder and results in lack of comfort and higher utilities. Flex duct is insulated from R-6 to R-10 and is sized to flow at no more than 600 feet per minute. When considering a flex duct installation, the system designer must take the airflow restrictions into consideration as he designs the system.

Hard Pipe

A hard pipe system, while more expensive is the recommended duct system by Central City Air. Hard pipe provides approximately 50% more airflow than flex. It is a quieter duct system, easier to balance airflow and due to the hard surface of the metal helps prevent mold growth. The reason a hard pipe system is more expensive than flex is because of its customization. Each hard pipe system is fit to the home's specific requirements, which requires each sheet metal section to be cut, screwed together, supported, taped, and wrapped externally with insulation. With a hard pipe system, air moves freely down the tubes and allows more flexibility in air balance. It is quieter and will not allow mold growth in the bare sheet metal of the runs. In our duct designs, we use internally lined duct for the supply and return air transitions and plenums. If mold or dirt accumulates in the air, it will show up in these areas. All other areas are externally wrapped. Thus, you have a very clean system that is designed to deliver you exactly what you need for a comfortable, efficient, healthy home.

Custom Hybrid

As stated above, ductwork carries air from the air plenum to the supply outlets. Silver flex ductwork installed correctly is a good duct system. Hard Pipe, sheet metal ductwork, properly designed and installed delivers air with the least amount of resistance. At Central City Air, we take a combination of these types of ductwork and custom engineer for superior airflow and comfort. Flex duct is insulated from R-6 to R-10 and is sized to flow at no more than 600 feet per minute. Our sheet metal ductwork is round, externally wrapped and sized to flow up to 900 feet per minute. A Hybrid system will provide up to 50% greater airflow than flex duct alone. The hybrid system takes the benefits from both types of ductwork and combines them to provide a custom, economical way to deliver your air from the system to the inside of your home.

Further Reading

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