Industry Articles From Kaempf and Harris

7 HVAC Ductwork Design Flaws To Look For Immediately


In 2015, according to the U.S. Department of Energy, the average HVAC duct system is only about 60 percent efficient. That means air isn’t flowing through your commercial building as it should be.

This can lead to undesirable consequences like the following:

  • Troublesome hot and cold spots
  • Drafts and stuffy indoor air due to impeded airflow
  • Extra wear and tear on your air conditioner in order to compensate for ductwork design flaws, leading to more breakdowns and shorter equipment life
  • Poor indoor air quality that exposes your colleagues to increased levels of dust, pollutants, fumes, and mold growth from too much humidity
  • Unbalanced air pressure that causes odors to linger, doors to slam on their own, and distracting levels of noise

Proper air conditioning ductwork can alleviate these issues and ensure that your commercial building’s HVAC system is running optimally, saving you time, stress, and money in the long run.

Here’s are some common mistakes found in ductwork design:

  • It’s poorly sized. According to Arista, an air conditioning company in Long Island City, NY, Many [sheet metal] contractors can make the mistake of failing to consider the type of air conditioning system your building has, load requirements of different rooms, where ducts and equipment are located, and the materials used to construct them.

    All of these factors affect the proper sizing of your ducts, and getting it wrong often means your ductwork is undersized.”

    Some contractors even take shortcuts by using the old duct system when installing new equipment. However, in most cases, the ductwork should be changed to ensure that it’s not leaking, it works well with the cooling unit, and it’s sized correctly. (Often times, the system should be larger than it was originally built.)
  • The runs are too long. If the location of equipment and HVAC ductwork design isn't optimized during the planning phase, the equipment may end up too far away from the space that needs to be cooled.

    This may constrain long runs of HVAC ductwork, which can decrease the system’s ability to move conditioned air to hard-to-reach areas. This results in troublesome hot and cold spots.

  • The bends are too sharp. Bends in the ductwork that are too sharp or too numerous also decrease the amount of air that reaches the space to be cooled.
  • The ducts aren’t sealed. Ducts that are incorrectly sealed or supported can end up leaking cooled air into the walls instead of rooms, which results in overheated building occupants.
  • Return vents are lacking. To maintain balanced air pressure and movement, the duct system needs return vents for air in the room to be pulled back into the HVAC system. Not providing enough return vents is a common HVAC ductwork design flaw that leads to comfort complaints.

    Another problem is placing return vents in useless spots like closets and other out-of-sight areas that are covered with boxes or furniture. When return air supply is restricted, the blower fan will try harder to pull the air in, which may shorten its lifespan significantly.
  • Cheap materials are used. Some contractors opt for tape instead of a more permanent solution. Other cheap materials can cause annoying noise, excess dust, drafts, and humidity problems.
  • The workmanship is poor. It’s possible for ducts to be assembled incorrectly, leaving air gaps and leaks. This increases your energy bill because cooled air is wasted.

An HVAC system is more than just a condenser, evaporator, and a furnace. It’s a complex system consisting of air ducts, air supply and return vents, insulation, ventilation, and many other aspects. Everything should be proportionate to your commercial building, so you can avoid overpaying for cooling and premature repairs and replacements.

For more information about ductwork design and sheet metal, download our Guide To Air Conditioning Ductwork:

Download The Ultimate Guide to Commercial Ductwork

Topics: Sheet Metal Fabrication

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