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Air Ducts 101: How They Work And Why They’re Important


Air Ducts 101

Air ducts are an integral part of your home’s heating and cooling system, which helps you keep your home at the perfect temperature no matter what time of year it is. They’re hidden away from sight, but they’re still worth getting to know, as they’re one of the most important parts of your HVAC system and contribute to good indoor air quality (or IAQ). Below you’ll find an introduction to how air ducts work and why they’re important in your home. Keep reading to learn more about this complicated-but-crucial component!

Ducts (Pipes And Trunks)

Every home has a network of ductwork that conveys heating, cooling, or ventilation air throughout your home. Some air ducts have heating elements in them. All are attached to registers that allow fresh air to enter your home from outside or return heated or cooled air from within your home back outside. Air passing through these pipes picks up dust and debris, so it’s important to use duct cleaning services for your duct system regularly, especially if you suffer from allergies or asthma.

Duct Transitions

Not all homes have duct transitions. These fittings are used to transition between different types of duct. Transitioning from metal duct to fiberglass duct (or vice versa) will cause a leak in airflow, so one should be installed every time there is a change in type of materials being used. So, make sure to put transition pieces on any joints you create between metal and fiberglass air ducting!


When you have an HVAC system, air is forced into a central heating/cooling unit. From there, it’s sent to vents in each room. But sometimes that air may not reach your rooms when you want it to because of duct. If you notice cold or hot spots in one or more rooms, there may be issues with your ductwork.


Placed at the end of air duct runs, flues transfer heat from your home’s furnace to your house’s heating system. Chimneys also carry excess combustion gases outside. If a flue is blocked or disconnected from a furnace or chimney, it can create back pressure that will either cause overheating or leave portions of your home cold. You should have flues inspected annually by a professional to prevent these issues.

Refrigerant Lines

These are insulated lines that carry refrigerant from your air conditioning unit to vents in various rooms of your home. The larger line is called a trunkline and it splits off into smaller ducts. These ducts are connected to registers, which ventilate heat out of a room as well as draw in cooler air from outside. A thermostat regulates temperature by shutting off your AC unit when a desired temperature is reached or when it falls below an acceptable range.

Air Handler

The air handler is really a big fan. It’s connected to your furnace or heat pump and pulls in outside air through return ductwork. Then it blows that air over cooling coils, which cools it down before blowing it back into your home through supply ductwork. If you have forced-air heating, you also have a blower motor that moves all of that warm air around. (The blower motor is usually located in your attic.)

Drain Pans And Lines 

These components capture water that condenses in your air duct system. The drain pans are generally round or rectangular slabs of metal; they’re fitted with holes that allow any water collected to drain into a gutter, downspout, or storm sewer.

Jacob Lindsey

Jacob is a home remodeling guru having worked over 15 years in construction in Reno, NV, mainly focused on home renovations. He likes taking ideas from his clients and making them a reality.

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