Noisy Ductwork

noisy air ducts, duct noise, quiet noisy ducts

Here at Las Vegas AC Repair, we go over what makes ductwork so noisy and how to fix it.

Noisy Ductwork

The most common reasons to hear noise in your HVAC ducts include:

  1. Air Pressure: A buildup of pressure can cause rumbling sounds. It can also cause the metal to expand and contract. When the system comes on, air pushes against the walls of ducts, expanding them. A popping or banging noise can often be heard upon startup. When the airflow slows down, the pressure reduces, causing the metal walls to pop back to their original shape.
  2. Closed Dampers: If dampers in your HVAC system are closed, pressure can increase, leading to various noises. This usually doesn’t happen by closing one damper. However, if you close multiple dampers, the system may become noisy, and closing too many supply vents can strain your HVAC equipment.
  3. Dirty Air Filter: If your air filters become dirty and clogged, it can affect the movement of air and cause noise. HVAC filters should be cleaned or replaced on a regular basis. Routine ductwork cleaning should be scheduled, as a buildup of debris can restrict airflow within the channels.
  4. Bent Flex Ducts: Many times, ductwork isn’t properly installed. This can cause it to sag or bend, making it harder for air to move. Static pressure therefore increases, and this, in turn, generates noise. If you are using flexible ducts, be sure that the contractor you hire is familiar with this type of ductwork installation.

Noisy Ducts Solutions

Believe it or not, noise from your air ducts can be reduced. There are practical solutions that you can use to address the sounds you hear and make your home a much quieter place.

  • Adjust Fan Speed: The amount of airflow should be configured during installation. But it’s not uncommon for an installer to set the fan speed too high. If this is the case, you may be able to lower the fan speed to reduce static pressure. However, it’s important to know what the proper airflow level is, as reducing it from a proper setting can lead to a lack of airflow to different rooms.
  • Install Larger Ducts: It’s possible your ducts aren’t large enough to accommodate the intended volume of air, even if other HVAC components are sized properly. You can install larger ducts or more of them to quiet things down. Installing larger return and supply plenums can help as well. Higher velocity registers and grilles can also cut down the noise by supporting more airflow.
  • Add a Bypass Duct: A bypass duct can relieve pressure in a multi-zone system. You should consult a ductwork installation professional, with experience in this type of work, to see if this is the best option. Reducing system pressure can be helpful in eliminating excess strain and lowering the risk of preventable issues.

Ductwork Many residential ducts are rectangular in shape and made from metal. When the heating or cooling system comes on, there’s an expected buildup in pressure within the ducts. we can inspect your HVAC system for any issues and make possible adjustments to help.

How can I reduce air duct poop and knocking noise?

Has anyone seen any dinghy houses or noisy vents? Imagine you’d like to sleep or read some scary movie and suddenly hear the sounds. That’ll make anyone angry! Unless ductwork makes a loud noise, nobody likes a loud knock noise in their house. Generally HVAC devices make noise at the moment that they are in operation but if it is loud enough to pop knocked or banged, it indicates an issue. When you turn on the heater or air conditioning system, the air vents start popping and banging. See the full article for tips for reducing noise and stopping it completely.

You’ll find that adding a few silencers will lower noise but not eliminate it. Variable Speed Blower Many homes are equipped with a single-speed blower for the air conditioning and heating system. Use rubber pads to isolate ducts from wood. Air conditioning noise can range from a low hum to a loud buzzing.

A quick word about hard pipe vs. flexible ductwork

Hard pipe ducts are louder as compared to flexible ducting. Air rushing into metal is even loud. Comparison to flexible ducts with no obstruction or bends will most likely make louder noises than with rigid tube ducts. Hard tube ducting has less kinks and bandings and therefore it can help with airflow. Flexible ductwork can have bends and cracks which cause faulty air circulation. Flex pipes = less noise and possible air circulation issues while hard pipes = greater noise and lower airflow issues. There are some tradeoffs. So there isn’t anything wrong with pipes being loud.


While it may cost you money to replace ductwork, cleaning a new ductwork will save you money. The reduction in pressures will soften the effect on expanding and contracting metal ducts. Get in touch with a professional HVAC contractor for duct cleaning sealing and insulation products including Acoustic / Aero-seal duct sealing or fiberglass insulation. Always hire professionals for cleaning duct work.


Air leaks can severely inhibit airflow from the room. The change in filters will help bring proper airflow throughout the system. If your air filters are not working properly, you will need to recheck them each 30-60 days.

Maintenance of Ducts

Fixing loud ductwork can provide a good way to keep your home quiet. If you’re not aware that the HVAC system’s noise is bad you shouldn’t fix this immediately and not fix the issue at that point in time. You should also maintain the duct work regularly. How do I keep my ductwork clean?

Short of covering all your ducts with fiberglass insulation, or opening them up and inserting acoustic duct liners, the best you can hope for is a modest reduction in the noise.

Look for leaks in the duct

Many of us don’t know what leakage happens in ductwork. Many homes use leaking ductwork to run heating or cooling appliances. Dirty ductwork can produce stifling noises, whistling or roaring. You must regularly inspect all your ductwork for holes resulting from leaking or noise.

When hot air from the furnace enters the ducts, they expand and, if they are rubbing against the framing, it can cause popping both when the metal expands with heat and when it contracts while cooling.

Problems To Fix

Have an HVAC technician check the system to make sure it’s not pushing more air than it was designed for. Contact us today to get your free quote.

LasVegas AC Repair

LasVegas AC Repair

With over thirty years of experience, we’ve been giving air conditioning, heating, pipes, as well as interior air quality solutions to the Las Vegas Valley. As a locally operated family company, we proudly serve our customers with stability and professionalism, and trust. We want you to end up being as well as stay part of our family.

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