How to Insulate Ductwork & Improve Energy Efficiency

Whether cranking up the air conditioning on a hot summer day or firing on the heat and warm air to beat the winter chill, homeowners often take their home’s ductwork for granted. At least until that monthly energy bill arrives in the mail. 

Then, it’s time to take a cold shower or huddle under an extra blanket—whatever it takes to keep those skyrocketing energy costs in check. 

While it’s always smart to be conscious of household energy consumption, other ways exist to improve energy efficiency rather than simply toughing out unpleasant temperatures. Learning how to insulate ductwork in the attic can be a major boon and energy saver to any home. 

Why Insulate Ductwork? 

Your ductwork is responsible for circulating warm and cold air throughout the home. If your ductwork isn’t properly insulated, the air moving through your home can be affected by external conditions that either heat or cool your home. As a result, your HVAC system must work extra hard to reach a comfortable temperature. 

In short, that means higher energy bills.1 

Furthermore, uninsulated ductwork can be prone to leaks. Besides overworking your HVAC system and straining your checking account, a leaking air duct can also result in:

  • More dust is being blown through the house
  • Strange odors and mustiness
  • Worsening allergies

Besides the cost, there’s no practical reason to leave attic ducts uninsulated. The cost of undertaking such a project will eventually pay for itself in monthly energy savings. This is especially true when air ducts are located in unconditioned areas like the attic. 

A Note About Moisture

Mold should be a frightening word to any homeowner. Because air ducts are made of thin metal, the cold air passing through them can often create condensation when exposed to warmer external air. Too much moisture in your HVAC system can create a breeding ground for mold and mildew. 

Simply insulating attic ducts can help to prevent mold in your crawl space or attic and spare homeowners from a variety of smelly and unhealthy problems in the future. However, we alos provide crawl space cleaning services to remedy any damaged crawlspaces.

Benefits to Insulating Ductwork

While we’ve already mentioned the energy savings that are possible with properly insulated ductwork, that’s not the only benefit of such a project:

  • Good for the environment – Insulated ductwork makes for a more efficient home, reducing your overall carbon footprint. 
  • Less strain on your HVAC system The air moving through insulated ductwork doesn’t lose its temperature as it travels through your house. That means your HVAC system doesn’t need to work as hard to reach your desired temperature, which in turn means your unit may last longer. Extending the life of your HVAC system should definitely be front of mind for the financially conscious. 
  • Better air quality – Because insulated ductwork is less prone to leaks, your air ducts are less likely to pull in dust or unpleasant odors from the unconditioned air outside your system. 
  • A quieter household Insulated air ducts lead to the HVAC system running less often, and when it is running, the movement of air through the ducts is quieter to curate a more peaceful household. 

Furthermore, while this can vary from state to state, there are often tax breaks available to homeowners who undertake insulation projects, especially when it comes to updating older homes. 

Choosing the Correct Ductwork Insulation

There are various types of duct insulation, however, the strength of each type of insulation material is measured by its R-value. The higher an insulation material’s R-value, the more resistant it is to external temperatures.2 As a rule, insulation with a higher R-value will cost more than one with a lower R-value. 

For example, here is a list of insulation materials sorted from lowest R-value to highest:

  • Loose (blown-in) insulation
  • Blanket insulation 
  • Spray foam insulation
  • Foam board insulation

The necessary R-value for insulation varies depending on where in the country you live. For example, in California, ceiling insulation must have a rating of at least R-30.3

Other Necessary Supplies

Once you’ve acquired the correct insulation, a few other supplies are necessary for this project. When working with fiberglass insulation, you will always want to have the following items for protection: 

  • Goggles
  • Long sleeves and pants (or other protective clothing)
  • A respirator face mask (ensure it’s approved for working with fiberglass)

In addition, you’ll need the following tools:

  • Measuring tape/measuring square
  • A sharp utility knife
  • Metallic foil duct tape (different from common duct tape)
  • Mastic duct sealant (depending on the condition of your air ducts; see below)

Sealing Leaky Ducts

Wondering how to seal ductwork? Before going through the trouble of insulating your attic ductwork, it’s important to make sure that your HVAC system is as uncompromised as possible. That means making sure that your air ducts are free of leaks. 

For a thorough rundown of how to check your air ducts for leaks, take a look at our guide on the subject. 

In short, leaky ductwork can hurt your HVAC system’s efficiency just as much as a lack of attic insulation. To find leaks in your system, you could:

  • Visually inspect your ductwork for kinks, cracks, or previously patched areas
  • Use soapy water or a smoke pen to detect where the air is escaping
  • Have a professional conduct a duct blaster test to pinpoint where your ducts are leaking

Any leaks you find should be sealed either with aluminum foil duct tape or, preferably, mastic duct sealant. Unlike tape, which can wear down over time, the mastic sealant will create a lasting seal on your air ducts. 

Insulating air ducts will cut down on future leaks, so hopefully, you won’t need to repeat this process in the future. 

Step-by-Step Guide to Insulating Your Ductwork

Now that you’ve checked your air ducts for leaks and acquired the proper safety equipment for working with fiberglass insulation, you are ready to insulate your attic ductwork. 

While the process seems pretty straightforward, it can get difficult in areas like the attic, where ducts might be hard to reach or at awkward angles. Don’t be afraid to consult with a professional if this task becomes too daunting for DIY. 

Step #1: Make Sure You’re Wearing Safety Equipment

We can’t reiterate enough how important it is to wear goggles, a breathing mask, and protective attire when working with fiberglass insulation. 

Step #2: Turn Off the HVAC Unit

Insulating your air ducts is a lot easier when they aren’t in use. Vibrating ducts can lead to slipshod insulation, so ensure your system is powered down before starting. 

Step #3: Measure and Cut the Insulation

Using a tape measure, determine the circumference of your air ducts. That’s how wide you want each piece of insulation to be. 

Then, using your utility knife and measuring square, cut off a section of insulation that is large enough to wrap around the ductwork’s circumference. Insulation doesn’t work as well when it’s packed tightly, so don’t try to force a too-small piece around your air duct. The insulation should fit snugly against the ductwork without stretching or crushing. 

Step #4: Seal the Insulation With Metallic Foil Tape

Once you’ve wrapped a section of your ductwork in the insulation, use a few pieces of tape across the gap to hold the insulation in place. Then, use another piece of tape down the entire length of the insulation to fully seal the gap to prevent an air leak. 

Remember to seal all gaps in the insulation with foil tape, including between pieces of insulation. If the insulation isn’t taped together securely, your results won’t be as desired. 

Step #5: Repeat the Process as Necessary

The project isn’t completed until you’ve wrapped every inch of ductwork with insulation. That probably includes some awkward joints and bends, especially if you’re working in an older attic. Make sure to measure each piece of insulation for total coverage properly. 

Step #6: Inspect for Gaps

Finally, once your air ducts are completely wrapped in insulation, inspect your hard work for any gaps you might have missed. Turning the HVAC system back on at this point can be a good idea to feel if any air is escaping.  

If you find any gaps in the insulation, simply seal them with tape. 

That’s it! You’ve now properly insulated your ductwork. It shouldn’t be long before you start noticing savings on your monthly energy bill. 

Let Attic Construction Save You Energy

Now that you’ve finished our guide, you hopefully understand why and how to insulate air ducts better. Without proper insulation, you could end up overpaying thousands of dollars every year in energy costs. 

If you’re interested in saving money but need help insulating your home’s air ducts, give the Attic Construction’s team a shout. Our local professionals working on air duct cleaning in San Diego, Orange County, and Phoenix areas, have decades of experience bringing down the costs of monthly energy bills by installing insulation you can trust will withstand the test of time. 

Stop burning money, freeze those energy costs, and call Attic Construction today!



  1. Department of Energy. Minimizing Energy Losses in Ducts.
  2. Forbes. What is Insulation R Value? Everything You Need to Know.
  3. California Energy Commision. 2019 Energy Code. 


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