Various Type Of Ducts

The most cumbersome part of a HVAC system is its duct work. These are long and broad pipes that snake throughout the house. Thy carry heated or cooled air in all rooms and discharge them through the vents and registers. If they are installed correctly and are of right size, they can play a key role in making a large building comfortable round the year. Here we will take a look at various types of ducts-

Types of Duct work

Ducts can be broadly divided into four types-

• Sheet metal ducts
• Duct board
• Flexible ducts.

Metal ducts: These ducts have been around since long. They are traditionally made of sheet metals. They are most expensive types among all categories of ducts. Their size and design needs to be customized according to the need of the house. They are also not insulated, which cause them to lose heat into attics, ceilings, and crawl spaces. That is why duct boards are being preferred over them. But cleaning them is easy with methods and tools used by duct cleaning services. They are also the most durable ones.

Duct boards: These are made of aluminium foil that is coated with a fiberglass insulation panel. They are easier and less expensive to install compared to sheet metal ducts. The duct work can be easily cut to size with a utility knife and shaped to meet the needs of the building. They are insulated. They are effective in dampening noises from HVAC. But they have some demerits as well. The fiberglass coating often starts coming out in shape of tiny particles and reach your living space with the air. Exposure to these can cause various health problems. In such cases the duct board needs to be coated with sealants to prevent chipping of the fiberglass. These boards if affected with molds cannot be treated to stop growth. It has to be replaced. According to expert Harriet Burge- "Fiberglass-lined duct work that is merely dirty (i.e., that has accumulated dust and dirt) can be cleaned if care is taken not to damage the fiberglass. However, if such duct work has become wet (that is, if mold is actually growing on the fiberglass), it cannot be cleaned. The mold penetrates into the fiberglass and will begin to grow again as soon as surface growth is removed. The use of biocides (agents designed to kill molds and bacteria) is not recommended in duct work because of the danger to the building occupants of exposure to the biocide."

Fibreboard ducts: They are made of fiberglass strands that are compressed and bound with resin, and then covered with a sheet of foil. However they can become a breeding ground for mold and mildew in humid climates. As they have rough surfaces, the airflow is a little affected.

Flexible ducts: They are used along with metal or fiberglass ducts. They are combined with main ducts to branch into individual registers. Installing them is easier and faster. They are also cheaper than metallic ducts. However, they allow lesser airflow on account of their smaller diameters. They often get constricted at places because of their flexible body which restricts the flow of air. You should stretch them well while laying them so that they are set straight without constrictions. They are not durable and get easily damaged. They require frequent replacements which compensate for the saving you make to buy them upfront.

A fourth type of duct is constructed by using spaces in walls and ceiling. Instant ducts are made by capping off a section between two studs. The same thing can be done in the floor joists. Objects like gypsum boards, sheet metals are nailed with joists or cavities to make rigid pathways of return or supply. In fact there are companies that advertise their insulating sheets that can aid in such practices. You should know that using building cavities as return air plenums is one of root causes duct leakage.



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