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The ductwork in your heating and cooling system provides the pathway that conditioned air travels from your furnace, air conditioner or heat pump to your home's interior. When this network of pipes is well maintained and sealed, the heated or cooled air produced by your HVAC equipment will easily reach your home's interior. If there are leaks in the ductwork, however, conditioned air will be lost. This leads to wasted energy and money, inconsistent heating and cooling, and inefficient HVAC performance. Following is a brief guide to ductwork and the main reasons it can develop leaks.

What Is Ductwork?

Ductwork consists of a large network of pipes, usually square shaped and made of a thin metal, that extends to points everywhere in your home. Ducts are usually installed under the floor, but can also be placed in areas above ceilings or near the top of rooms. Supply ducts provide a pathway for conditioned air leaving your HVAC unit, while return ducts bring stale and exhausted air back to the system to be filtered, reconditioned and redistributed.

Symptoms of Leaky Ductwork

  • Unexpected spikes in heating or cooling bills that cannot be traced to increased HVAC system usage.
  • Problems keeping particular rooms warm or cool.
  • Rooms or areas that are too warm or cool for the season.
  • Areas of your home that are stuffy or uncomfortable.
  • Increased amounts of airborne dust and particulates.
  • Visible damage to ductwork.

Reasons for Ductwork Leaks

Ductwork leaks can account for anything from minor air losses to the loss of all the conditioned air traveling through the ducts. Ductwork should be inspected and repaired during annual HVAC system maintenance. Duct leaks can be caused by:

  • Age and gravity: Simple age and the constant pull of gravity can cause ductwork to loosen and seals to break. Adding supports to ductwork sections can help prevent this, but eventually, it's highly likely a leak will develop somewhere within the duct network.
  • Broken seals: Ducts consist of several interconnected sections of pipe. The connections at each section should be sealed with a specialized sealant called mastic or with metal tape. The sealant prevents air loss and helps hold duct segments together. If the seals between duct segments are broken, air and energy will be lost.
  • Loose or detached ductwork: Similarly, ductwork segments should fit tightly together at all connections, especially at elbows and joints. Ductwork is designed to provide this tight fit, but damage, wear or age could cause the segments to come loose. A detached segment of ductwork anywhere in the system could cause almost all of the conditioned air in the duct to be lost.
  • Ducts installed in unconditioned areas: Ducts in unconditioned areas, such as crawl spaces or garages, have a greater likelihood of developing leaks. In addition, energy can be lost through the thin metal of the ductwork itself. Ductwork should be insulated and diverted away from unconditioned areas wherever possible.
  • Lack of mechanical fastening: Duct segments can be given additional strength by mechanical fastening at each connection. If these fasteners become loose or damaged, the ductwork segments are more likely to develop leaks or come apart.
  • Rodents and animals: Ductwork can serve as shelter to mice, squirrels, rats, or other rodents and small animals. As these creatures move around within or on the outside of the ducts, they can cause seals to break or segments to become loose.
  • Zone pressurization: Rooms and areas inside your home can develop pressure differences that cause air to leak from ductwork. Inadequate supply and return ducts or the lack of enough return registers can make the problem worse.

Our goal is to help educate our customers about Plumbing, HVACR, Fire Protection and Alarm Systems in Mechanical, Commercial and Residential settings. For more information on the main reasons for ductwork leaks and how to prevent or fix them, and to view projects we've worked on, visit our website!

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