What Are Air Ducts? Understanding Your Home’s Ductwork

If your home has central air, then your air ducts are essential in keeping you cool in the summer and warm in the winter. These ducts connect with your HVAC system and help to facilitate airflow throughout your home. Because they can influence your home’s air quality, air ducts must be clean and functional.

What Are Air Ducts and How Do They Work?

Air ducts deliver heated or cooled air to different areas in your home. If your home has an HVAC system, they also regulate the temperature. The same duct system carries air from both the AC and the furnace. They’re commonly made of galvanized steel, aluminum, or fiberglass.

Where Are Air Ducts Located?

Air ducts are installed behind a home’s walls, floors, and ceilings. They connect to the HVAC unit and move the air invisibly through the house to each room. You can tell where your home’s ducts are by the location of your air vents. If the vents are in the floor, your ductwork likely runs underneath the room. If they are in the ceiling, your ductwork is above the room.

Types of Air Ducts

Here are the main types of ducts you can use in your home. Usually, homes have a combination of flexible ducts and sheet metal, fiberglass-lined, or fiberboard ducts.

Sheet Metal Air Ducts

Sheet metal air ducts are durable, non-porous, and easy to customize during installation. Manufacturers commonly make these with galvanized steel, stainless steel, or aluminum. All these metal types are resistant to mold and corrosion, although rust can form without proper maintenance.

These air ducts are also easy to clean, maintain, and repair. They aren't affected by extreme temperature changes and are very durable.

Sheet metal air ducts cost $7 to $13 per linear foot for materials only. Additionally, labor costs for installation tend to run higher for sheet metal air ducts than other duct types. 

Fiberglass Lined

Fiberglass-lined air ducts are metal ducts with fiberglass lining, either on the interior or exterior. The fiberglass helps as a sound and thermal insulator. This type of duct costs $7 to $13 per linear foot for materials.

It's important to maintain your fiberglass-lined air ducts properly. Over time, the primary seal on the ducts can wear down from extreme temperature changes. When the seal breaks down, raw fiberglass fibers can enter the airstream.

This is avoidable with preventative maintenance and a regular cleaning schedule. It's possible to repair, replace, or remove the liner as necessary. It’s also a good idea to consider installing a high-efficiency air filtration system if you use fiberglass-lined ducts.

Fiberboard Air Ducts

Manufacturers make fiberboard air ducts from flat sheets of resin-bonded fiberglass. They have an air and vapor barrier on the exterior, and some have an antimicrobial coating on the interior. This option also offers sound and thermal insulation and costs $4 to $6 per linear foot for materials.

Flexible Air Ducts 

True to their name, flexible air ducts are easily bendable thanks to a bendable polymer plastic lining with round wire coils inside. HVAC pros commonly use them to branch off the main HVAC system and deliver air to different rooms in the house. Correct installation is key to preventing flexible air ducts from sagging over time. 

Insulated flexible air ducts cost $2 to $4 per linear foot for materials, while non-insulated flexible ducts cost $1 to $3 per linear foot.

How to Maintain Air Ducts

A home’s air ducts are relatively low maintenance, but there are several things you can do to keep them in good working order. 

Regularly vacuuming and dusting your home helps prevent debris from being sucked into the return air vent. This vent removes warm or cold air from a room and returns it to the HVAC unit to be reheated or cooled before circling it back through the home. Limiting the amount of dust and dander that’s sucked into your ductwork can also keep your HVAC filter cleaner for longer.

Speaking of the filter, make sure you change it at the intervals recommended by the manufacturer (typically 90 days). If you notice excessive dust or debris in your home, you might need to clean your air ducts to keep them in good shape.

Signs Your Air Ducts Need Cleaning

Do you remember the last time you got your HVAC ductwork cleaned? Here are some signs it's time to clean your air ducts.

• Little to no airflow suggests that your air ducts are dirty. You might notice that your home isn’t heating or cooling as quickly or that there’s a noticeable temperature difference between rooms.

• Loud noises like rattling and whistling can signal a problem. Cleaning the ducts may solve the issue, or you might need duct repair.

• Low indoor air quality can exacerbate allergy and asthma symptoms. Duct cleaning can help improve your home’s air quality.

• Increased utility bills could indicate dirty air ducts. When your ducts are dirty, your HVAC system has to work extra hard to cool or heat your home. 

• Dirty vent covers suggest there’s a lot of dust in your ductwork. While it’s normal for the vents to collect a small amount of debris, an excessive amount is cause for concern.

• Signs of rodents or insects, including running and gnawing sounds in your walls or ceilings, suggest you need air duct cleaning (as well as pest control services).

• An unpleasant odor from your air vents, such as mustiness or burning, suggests dirty ductwork. A burning smell is likely the accumulated dust burning off in your ducts as hot air passes through it, while mustiness suggests mold or mildew growth.

Why Air Duct Cleaning Is Important

The frequency of air duct cleaning isn’t an exact science. The Environmental Protection Agency only recommends cleaning air ducts if there’s an issue like mold, dust, or rodents. However, experts recommend cleaning your air ducts every three to five years. 

The exact frequency depends on where you live, how often you use your HVAC, and whether people in your household have sensitivities. If you need to have your ductwork cleaned, an air duct cleaning company near you can help.

How to Spot Signs of Mold in Your Air Ducts

If there’s mold in your air ducts, you could be breathing in tiny mold spores without realizing it. Common signs of mold include a musty smell, visible mold on or near HVAC components, and physical side effects such as nausea, fatigue, runny nose, coughing, and sneezing.

How Much Does Air Duct Cleaning Cost?

Heat and AC ducts cleaning costs about $390 on average, but can range from $270 to $500. This includes the cost of inspecting your HVAC system and cleaning all relevant parts. Hiring a pro for this job is definitely an expense, but many deem air duct cleaning worth the money—especially if they have severe allergies.

Looking for a more affordable DIY solution? Regularly checking and changing the filters in your HVAC system is a more effective way to improve air quality than cleaning your air ducts.

When to Repair vs. Replace Ductwork

There are a few things to remember when deciding whether to repair or replace your ductwork. Ductwork that’s in good shape and less than 15 years old can often be repaired. Some common repairs include replacing vents, sealing minor leaks, patching holes, and reattaching loose ductwork. Depending on the cause of the issue, ductwork repair costs $200 to $2,100.

Ductwork older than 15 years is more likely to need replacing. Replacement is also recommended in cases of severe damage. For example, if your house floods, you may need to replace your ductwork if the water reaches so high that the ducts are completely underwater. If the water didn’t reach your ducts, consider replacing any insulation.

Even if you don’t deal with anything as severe as a flood, you need to take action if you notice mold or mildew growing on your ductwork’s insulation. If an HVAC pro cannot clean it, you may need to replace the ductwork altogether to avoid future mold regrowth. Air duct replacement costs between $450 and $2,190.