How Leaky Ductwork Affects Your Home’s Indoor Air Quality

Your HVAC system is an essential piece of home equipment consisting of many parts, including indoor and outdoor units, vents and a system of ducts. If it’s not functioning properly and efficiently, the issue could be located in any one of these components. Unless the HVAC unit completely stops providing your indoor space with conditioned air, one of the best places to start looking for problems is in your air ducts.

Duct leaks are one of the most common issues homeowners face when it comes to their HVAC system. The presence of cracks or holes in one of the ducts can affect not just your home’s comfort levels, but also the air you breathe inside your home. Here local contractor MLD Services explains everything you need to know about the relationship between leaky ductwork and indoor air quality (IAQ).

About Leaks in Your HVAC Ductwork

Duct leakage occurs when conditioned air gets distributed from heating or cooling equipment and leaks through the cracks, holes or seams in the ductwork before it reaches the desired spaces in your home. According to the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), about 75% of buildings have this problem. On average, most homes leak up to 25% of their conditioned air.

A 2018 article published in the Journal for Light Construction (JLC) highlights the following types of duct leakage:

  • Supply Leakage – Leaks in the supply air ducts cause decreased airflow from the main HVAC unit to the desired room or space.

  • Return Leakage – Leaks in the return air ducts cause the ventilation system to suck in unconditioned air from the attic and wall cavities and distribute it back into the main HVAC unit. This can affect the equipment’s performance because of the additional load.

  • Equipment Leakage – This type of leak is arguably the most overlooked. Components such as coil cabinets and furnace cabinets have “seams” that suck or blow air. The lack of seals in these areas can lead to decreased airflow from the main unit to the room or space.

Duct leaks can lead to a variety of HVAC problems. Since rooms or spaces aren’t receiving adequate amounts of conditioned air, expect one room to be cold while another on the same floor is hot. Uneven temperature distribution affects not only your home’s indoor comfort but also your unit’s efficient operation.

Also, duct leaks can lead to a spike in your energy bills. They put increased pressure on the HVAC system that’s often more than it can handle. Expect an increase in your energy consumption if these leaks aren’t sealed as soon as possible. If you encounter any of these issues, you must get in touch with your local HVAC services provider, who can inspect your ductwork and perform the necessary repairs.

The Correlation Between Duct Leakage & IAQ

Duct leakage can have a lasting effect on your home’s indoor air quality. Excessive dust, dirt and airborne allergens can render the air inside your home unfit to breathe, which can cause a wide range of health issues, especially ones that affect the respiratory system.

Here’s a look at the top reasons why leaky or damaged ducts are a bad thing for your home’s indoor air quality:

  • Sucking In Bad Air 

The presence of leaks or gaps in the return ducts can allow airborne outdoor contaminants to get into the ventilation system while the HVAC system is in operation. They can also suck in bad air from musty spaces around your home like the attic, basement and crawl space. This is a bad thing because the unfiltered air can find its way to the rooms or spaces that need heating or cooling. Checking the condition of the return ducts and repairing any gaps or leaks are imperative in ensuring they don’t pull contaminated air into the unit.

  • Creating Negative Pressure

Leaks in the supply side of the ductwork create negative air pressure inside your home. As the unit tries to balance the air filtration, infiltration from the outdoor air increases as a result. More air will leak into the house through your windows, doors and other musty spaces in your home if the amount of air being supplied through the ducts is less than the amount that went into it. Indoor pollutant levels will then increase because of the unfiltered air being distributed.

  • Increasing the Risk of Backdrafts

HVAC equipment that uses combustion, like a water heater or furnace, utilizes a flue or chimney to allow harmful gases to exit your home. However, due to negative pressure in the air around the unit, the gases can get pulled back indoors through backdrafting. Pressure imbalances can occur when there are leaks in the return ducts or the rooms near the central return vent are closed. Carbon monoxide levels may then increase, causing your alarms to go off—if you have them installed in your home in the first place, that is.

The Importance of Ductwork Repair

Improving your duct system starts with regular HVAC maintenance. After all, well-designed and properly-sealed ducts help ensure your home’s comfort, safety and energy efficiency. Although some homeowners consider duct repairs to be a do-it-yourself project, it makes more sense to work with a professional HVAC contractor who has the expertise and experience to fix ductwork issues.

Even if the ducts are installed behind walls or in ceilings, attics and basements, the pros utilize methods that enable them to check for inconsistencies in airflow. Air duct testing is one of them. Generally, this process involves the use of three components: a calibrated fan, a register sealing system and a reader or device that measures fan flow and pressure. This can be performed by either pressurizing or depressurizing the ducts to determine if they’re airtight enough. The tighter they are, the fewer gaps or holes they have, which means less air is needed from the calibrated fan to create a pressure change.

MLD Services is a leading AC and heater installation contractor in the local area. We specialize in air conditioning and heater installation services, as well as HVAC repair and maintenance. We also work on improving your home’s indoor air quality through our ductwork repair and testing services. Give us a call at (512) 607-7400 or fill out our contact form to request an estimate.

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