You may have heard of a duct leakage test in Colorado, and you might be wondering if it is required for your new home. In this article, we’ll discuss the test, when it is required, how it is performed, and what you’ll need to do to pass. Let’s get started.

Understanding When Duct Leakage Testing is Required In Colorado

Duct leakage testing was first required by the 2015 IECC building code. This means that any Colorado counties or cities that have adopted the 2015 IECC (or any subsequent iterations of the code) are required to perform duct leakage testing on all new homes or additions with duct systems. According to the 2015 IECC and 2018 IECC, duct leakage testing is only required on ducts that are located in areas outside of the conditioned space, such as:

• An attic
• An uninsulated crawl space
• A garage
• An exterior utility room
• A garage attic

Essentially, if any piece of the system is outside the heated space, you will need to perform the test. Even if there is just one flex line going through an attic, or an unconditioned crawl.

The 2021 IECC duct leakage testing rules are similar to the 2018 and 2015 IECC, except for one very significant difference.

If you look at the “exceptions” in the R403.3.3 Duct testing section of the 2018 IECC, it states: “a duct air-leakage test shall not be required where the ducts and air handlers are located entirely within the building thermal envelope.”

But if you compare that to the R403.3.5 Duct testing section in the 2021 IECC, the above mentioned “exception” has been removed all together. This means that, under the 2021 IECC building code, all air-handling ductwork will need duct testing, even if it does not run outside the thermal envelope of the home. 

Need a duct leakage test performed? Learn more and schedule one today!

How Is The Test Performed?

Using a special fan, air is pumped through your ducts at a specified pressure of 25 Pascals, equivalent to 0.1 inch w.g. (Water Gauge). All of your registers will be sealed during the test. The sealing is performed with special HVAC tape, but many times HVAC contractors will seal the ducts during construction as well. Learn about the best ways to prep for the test here.

By measuring the fan output and the amount of additional air pressure required to maintain the proper pressure in the ducts, the total amount of leakage in your duct work can be measured. When a duct leakage test is required in Colorado, these are the necessary steps taken.

What Counts As A “Pass?”

To pass the test, your home must meet the following test results. Note that numbers 1 and 2 are required by the 2015, 2018 and 2021 IECCs. Whereas, number 3 is only required by 2021 IECC.

1. Rough-in test – If the air handler has been installed, leakage must be less than or equal to 4 cubic feet per minute, per 100 square feet of conditioned floor area. If the air handler is not installed at the time of the test, leakage must be less than or equal to 3 cubic feet per minute, per 100 square feet of conditioned floor area.
2. Post-construction test – Total duct leakage must be less than or equal to 4 cubic feet per minute, per 100 square feet of conditioned floor area. In addition, building framing cavities cannot be used as ducts or plenums, and any mechanical piping carrying fluids over 105 degrees Fahrenheit, or under 55 degrees Fahrenheit, must have a minimum insulation level of R-3.
3. *Additional Rule for 2021 IECC* Test for ducts within thermal envelope: Where all ducts and air handlers are located entirely within the building thermal envelope, total leakage shall be less than or equal to 8.0 cubic feet per minute, per 100 square feet of conditioned floor area.

If you do not pass, your ducts may need to be reworked, or sealed, to reduce air leakage and ensure compliance with the building code in your jurisdiction. In many cases, installing AeroSeal can help seal the system, if the ducts have difficulty passing the test.

For more info about the 2021 IECC Duct Leakage Testing update, check out this article.

Know The Basics About Duct Leakage Testing – And If It’s Required For Your Home!

A properly-built new home will have no issues passing IECC duct leakage standards. So make sure you know what to expect from your duct leakage test, and prepare accordingly – you’re sure to pass with flying colors. We can help with fast scheduling and experienced technicians when you order a duct leakage test through Scott Home Services.

At the time of this writing, most Colorado counties have adopted the 2018 IECC 0r the 2021 IECC. These energy standards have established that a number of field tests are required to validate the energy performance of a home. This includes blower door testing and duct leakage testing – both are important tests for evaluating residential energy efficiency. In this article, we will take a closer look at duct leakage testing in Colorado.

IECC Duct Leakage Requirements

When it comes to duct leakage testing, the 2018 and 2021 IECC rules are very similar, save for one key difference. In the 2018 IECC, Duct leakage testing is not required on any part of the duct system that is located within the thermal envelope of the building. This rule is consistent with the 2015 IECC. On the other hand, according to section 403.3.6 item #3 of the 2021 IECC, now all ducts must be tested – even if they are within the thermal envelope.

For more information about the 2021 IECC duct leakage code updates, check out our article, Duct Leakage Testing Requirements in 2021 IECC Codes

Testing is required to be performed by an independent third party. The code applies to new home construction and remodels/additions in some municipalities. These rules will vary from county to county, based on what IECC version has been adopted. So its always a good idea to check with the local building department to see what is required.

Purpose of Duct Leakage Testing:

• Studies show that a typical duct installation loses up to 20% of the air before getting to the registers. If that air happens to leak outside the building envelope, the overall comfort of a home can be compromised, and high utility bills will likely ensue.
• When air is blowing through ducts outside the conditioned space of the home, this can cause a change in pressure between the heated and unheated areas. This can lead to more air movement between the two areas which will transfer heat/cool air outside of the home.
• Leaks in ducts can pull in air from these unconditioned areas. High pressure in an attic, for example, can push dirty or dusty air into the home through small gaps in the ceiling.
• Within the home itself, unbalanced air flow caused by duct leakage can pressurize or depressurize zones causing rooms to be stuffy or to have temperature variation.

When is the best time to do a duct leakage test?

Duct leakage testing can be done during various stages of construction and still meet the specifications of the energy code, although we recommend performing it at rough-in when access is easiest. This also gives you the ability to seal sections of the ducts while they are still exposed.

How do we perform the test?

We use the “Duct Blaster” to test the air supply and quantify leakage. We seal off all the registers in the home and run a fan at a return, or at the air handler to depressurize the system. The total amount of leakage in the system is determined by pressurizing or depressurizing the system with the Duct Blaster to 25 pascals.

Click here to view a great article about duct leakage tests from the air leakage pioneers, The Energy Conservatory.

What Comprises a Pass or a Fail?

The threshold for passing the test is determined by a certain number of CFM of leakage per 100 square foot of conditioned space that the system serves. Here are the baseline numbers given in the IECC 2015 codes.

• 3 CFM per 100 SF – Rough-in—with no air handler installed
• 4 CFM per 100 SF – Rough-in—with the air handler installed
• 3 CFM per 100 SF – Post-construction—with no air handler installed
• 4 CFM per 100 Sf – Post-construction—with the air handler installed
• 8 CFM per 100 Sf – Post-construction—with the air handler installed and all ducts within the conditioned envelope (2021 IECC)

Helpful hints to pass your Duct Leakage Test:

• If this is your first test, always have it performed at the rough-in stage so that issues can be easily addressed.
• Liquid Mastic or “pookie” has shown the best results based on our experience.
• Seal every joint. The test is very sensitive, so the HVAC professional may need to seal quite a bit more than normal.
• The furnace or air handler is often overlooked. Seal around the edges and around the back side of the handler where the returns connect.
• Flex duct is popular in attics. However, the zip ties conjoining them to the system have a tendency to leak. Add mastic to these joints as well to create a tight seal.
• Make sure the filter cover is fully installed and sealed before the test.
• Do a once over of the full system before the test to identify weak or unfinished areas.
• It can be helpful for the HVAC installer to be present during the inspection to help identify and repair leaks on the spot.

Scott Home Services

At Scott Energy Services, a division of Scott Home Services, we have a team of highly trained energy efficiency and air leakage specialists. We offer an extensive list energy services including Duct Leakage Testing, Blower Door Testing, HERS Ratings and more! So whatever your building requirements may be, we are here to be of service.

For more information or to schedule a duct leakage test with Team Scott, click here.