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When was the last time you had your HVAC systems air ducts inspected or cleaned? If you’re like most homeowners, the answer is, “never.” 

While loft spaces and some contemporary home designs leave ducts exposed, most homeowners live in buildings with ducts that are craftily hidden in attics, soffits, and crawl spaces. As a result, they are largely an afterthought, or a non-thought, compromising home comfort and energy efficiency and negatively impacting indoor air quality (IAQ).

9 Signs Your Air Ducts Need Replacing Or Repair:
Here are some of the signs your home’s air ducts need attention, which could include a good cleaning and some minor repairs or a full-blown replacement.

  • 1: Your home or HVAC system is 20+ years old
  • HVAC duct system design has come a long way in 20 to 30 years. What used to be left to “rule of thumb” tenets based on the square footage of a home has now an evolved mathematical algorithm based on a range of factors and features about your home.

    Rather than saying your home needs X feet of Y-sized ducts based on its square footage, HVAC technicians use a software program that inputs various factors to determine the size, length, and duct design for optimized comfort and efficiency. This includes things like:

  • • Square footage
  • • Home orientation on the lot
  • • Windows/door specifications
  • • Insulation specifications
  • • Ventilation system
  • If your ducts are more than 20 years old, we recommend scheduling an appointment with a local HVAC contractor to have your system re-evaluated. Odds are, the entire system needs to be replaced.

  • 2:Have you touched your ducts in 10 years?
  • Ten-year-old ducts may be designed and installed correctly, but much can happen in functional mishaps within that time frame. Depending on the materials used and the airflow, ventilation, and humidity levels in your home, ducts may acquire rust and mildew, compromising their structure and circulating unhealthy mold/mildew spores through the forced air system.  Unmaintained ducts are at risk for:

  • • Cracked, separated, or completely disconnected sections
  • • Missing or dilapidated insulation
  • • Corroded seals
  • • Dirty or blocked vents
  • • Leaks 
  • Your attic specialist can attend to these issues and make your ducts as good as new again.

  • 3: They haven’t been cleaned in three or more years
  • Some companies would have you believe ducts need to be cleaned at least once per year. This isn’t necessarily the case assuming your HVAC is regularly maintained and that you replace the air filters as per the manufacturer's recommendations.

    Even so, ducts slowly acquire dust, allergens, and other particulate matter over time, leading to blocked airflow and compromised indoor air quality. Therefore, we recommend getting your ducts cleaned at least every three to five years. The good news is that those cleanings also give ducts a chance to have an inspection, so any red flags are attended to sooner rather than later.

  • 4:Reduced HVAC airflow
  • Is your HVAC system cycling on and off more frequently than usual? Have you noticed the vents aren’t blowing the same amount of air as they used to? Do energy bills seem higher than they have been in the past for the same thermostat setting?

    All of these are signs of reduced HVAC airflow that may originate from the ducts. Any leaks, gaps, or blockages disrupt the flow of air through the ducts, and this takes a toll on your HVAC system and energy spending. 

  • 5:Reduced heating or cooling
  • Similarly, you may notice that the HVAC is running, but it’s taking longer than expected to get your home to the desired thermostat temperature. Any reduction in heating or cooling could result from damaged or outdated ducts. You should attend to this immediately because the harder your HVAC system works, the more expensive your total system maintenance, repairs, and replacements are over the lifetime of your home. And, of course, a constantly and unnecessarily cycling HVAC means you’re burning excess energy.

  • 6:Do air ducts need replacing if they are dented?
  • Some homeowners prefer to perform DIY attic, insulation, and duct inspections. We applaud this and want to make sure you don’t write off critical red flags. For example, dented ducts that are still sealed, connected, and otherwise appear in good shape may not seem like a big deal. Air can still flow right through them, right?

    Actually, dented ducts mean obstructed airflow, which takes us right back to #4 and #5 - reduced airflow, reduced heating/cooling, and compromised energy efficiency. However, duct sections are fairly cheap to replace, so your small investment to replace any dented sections is returned to you in reduced energy spending.

  • 7: Odd or unpleasant odors when the HVAC is running
  • If you have dirty or moldy/mildewy ducts, odds are you’ll notice interesting odors when the forced air system operates. If it’s moldy/mildewy, you’ll notice a musty or damp smell. If you have a pest infestation, current or former, you may even smell a hint of urine or mousey scents. In any case, an HVAC system should operate largely odor-free. If you notice unpleasant or unusual smells, it’s worth examining the ducts.

  • 8: What’s that noise?
  • If ducts are in a state of disrepair, you may notice a whistling or hollow noise when the HVAC system cycles on. Any random thunks, clunks, or bumps are also a red flag. While some noises are the fault of the HVAC unit, others may be the result of poor or compromised airflow. And the former often causes the latter, so either way, your system deserves a checkup.

  • 9: The registers and grilles are worse for wear
  • The ducts, registers, and grilles are typically installed at the same time. They are the “caps” that create a more sightly appearance than a vacant hold in the wall and they also form the final line of defense to keep any errant objects in the duct system from flying into your home. If the registers or grilles are loose, damaged, or look worse for wear, odds are the ducts need attention as well.

author : Stone Si

Founder, owner, and project manager for Stone Insulation Services, Stone provides guidance and leadership for his team and his clients. Utilziing his training, product research and environmental testing; Stone applies his findings to each and every job. Doing so, he occasionaly writes on topics frequently asked through his daily duties.