If you are in the building industry, you are no doubt familiar with the International Energy Conservation Code (IECC).  This code is used as an industry standard for new building projects and renovations. And it establishes what guidelines need to be followed in order to meet code. As an Energy Services company, we make it our business to stay in-the-know about any IECC updates or changes. That is why we are going discuss the recent changes to duct leakage testing requirements within the IECC 2021 version.

But before we dive into the IECC changes, let’s first discuss duct leakage testing and what it is…

What is Duct Leakage Testing?

Simply put, the purpose of duct testing is to evaluate how well a home’s duct system can hold air. The more leaks your duct system has, the less efficient it will be.

A leaky duct system will result in wasted energy and wasted money. Furthermore, poorly sealed air ducts can cause unevenly distributed heat or AC throughout the home, resulting in an uncomfortable living environment.

At Scott Energy Services, duct leakage testing is one of our primary energy services. Most counties in Colorado adhere to the IECC standards, and thus, the duct leakage protocol. As a result, we have performed hundreds of these tests with our tried and true method!

How Does It Work?

To begin, all duct openings (including supply and return registers) must be sealed off with specialized HVAC tape. A large fan is then sealed securely to the air handler opening or a large return opening (as shown above). However, this is usually done at rough-in on new construction homes.

We run the fan to depressurize the duct system down to -25 pascals. The amount of air moving through the fan is then calculated. This number, referred to as the CFM25, indicates the amount of air leakage in the duct system.

For more details about our duct leakage testing process, you can check out our website.

How Did the IECC 2021 Codes Change Duct Leakage Testing?

Believe it or not, just one sentence was removed from the 2021 IECC duct testing section. However, this one change makes a BIG difference.

If you look at the “exceptions” in the R403.3.3 Duct testing section of the 2018 IECC, it states that “a duct air-leakage test shall not be required where the ducts and air handlers are located entirely within the building thermal envelope.” This is consistent in IECC 2015 codes as well.

The reason this initial exception existed was because if duct leakage occurred within the thermal envelope, heated or cooled air could still be captured to a certain degree.

Now compare that to section R403.3.5 Duct testing in the 2021 IECC, and that statement has been removed. This means that, in jurisdictions that have adopted the 2021 IECC, all air-handling ductwork will need duct testing, even if it does not run outside the thermal envelope of the home. For homes with more than one HVAC system, both systems will need to be tested.

This is big news, and it might be a bit of a curveball for some builders. This is because it has never been a requirement, since the IECC’s inception of the duct testing rule in 2015.

When comparing ductwork that remains within the thermal envelope to ductwork that exits the thermal envelope, leakage requirements differ slightly. According to section R403.3.6, leakage for duct systems that leave the envelope of the home, must not exceed 4.0. cubic feet per minute per 100 square feet of the conditioned floor area. On the contrary, ducts that remain within the thermal envelope must be less than or equal to 8.0 cubic feet per minute per 100 square feet. So there is slight bit more leniency when it comes to ducts within the thermal envelope.

Builders who haven’t needed this type of testing in past projects now must factor it in. They must be sure not to skip over this stage of testing during their projects. It will also contribute to a marginal increase in costs that must be factored where necessary.

What Are the Benefits Of This Change?

This updated code might ruffle some feathers. But from an energy efficiency standpoint, this rule does have its benefits. One of our certified HERS raters, Joe Ophoff, spoke on the matter:

“In new construction home design, there is a great emphasis on air leakage and distribution.  New homes are designed for super performance, so really fine-tuning distribution systems are necessary for comfort throughout the house. Too much duct leakage can indicate a failure in the installation of the duct system, so we can catch a bad install at the ‘rough mechanical’ phase to ensure things are installed correctly. But also, the duct designs are carefully calculated to ensure distribution equilaterally throughout the house, so any significant leakage would affect that.”

Joe illustrates this point well – it all comes down to energy efficiency and optimum HVAC performance. If your interior ducts have too much leakage, they might not evenly distribute heat/air throughout the house. So when you get the system tested during the building process, you are able to pinpoint any issues and have them addressed before the project is finished.

In many counties across the country, including most in Colorado, Manual J/S/D reports are required to get a permit. These reports design the duct system prior to installation; and they calculate the perfect amount and balance of airflow and velocity for each room of the home. However, these reports assume the presence of well-sealed ducts for the results to match the initial calculation.

So this is another step in the process of engineering a super comfortable home for the homeowner, and ensuring everyone is getting the most out of the energy they are using. We wouldn’t be surprised to see actual airflow balancing or velocity testing requirements in the future to even further verify the performance of the duct systems.

In Need of Energy Services?

At Scott Energy Services, a division of Scott Home Services, we are seasoned duct leakage experts. But that’s not all. We also have a number of other energy services, including energy audits, HERS rating, blower door testing, REScheck report services, insulation inspections and air barrier inspections. And we make sure to stay up on the ever-changing codes, in order to help you move along through your project without a hitch.

But what’s a good duct system without the right mechanical design? As you likely know, the IECC requires all new builds and additions to submit a Manual J, S, and D report to ensure mechanical design code compliance. This is another service that we proudly offer. If you need a Manual J/S/D report, we a have team of experts ready to help!

No matter what your next building project needs may be, we would love to be of service! Visit us online to learn more or contact us to book your services today.

If you are a contractor, builder or architect in Larimer County, CO, you are probably aware that the area has adopted the 2021 International Residential Code (IRC). This is a series of rules established by the International Code Council (ICC) to which all new residential building projects must adhere.

As of March 2022, several amendments were added to the overall IRC. And Larimer County has opted to adopt these amendments, as well. One of the big changes is that air barrier inspections are now required on new builds.

Building Envelope Performance Verification

The state of Colorado is constantly striving to increase statewide sustainability. That is why factoring in energy efficiency is a major part of the CO residential building process. It is no surprise then that many counties, including the Larimer County, have adopted the energy-related guidelines of the IRC. Chapter 11 of the IRC focuses on energy efficiency.

One of the primary amendments to this chapter now requires “building envelope performance verification.” This means that, before siding is added to a home, a certified inspector must examine and approve its exterior air barrier. Additionally, an air leakage test must be conducted on the home upon completion to make sure it meets energy efficiency requirements. The excerpt below highlights the key points in the amendment:

1. A review of the construction documents and other supporting data shall be conducted to assess compliance with the requirements in this section.

2. Inspection of continuous air barrier components and assemblies shall be conducted during construction while the air barrier is still accessible for inspection and repair to verify compliance with the requirements of this section and Table N1102.4.1.1.

3. An air barrier and air sealing inspection report shall be provided for inspections completed by the approved air leakage testing agency. The air barrier and air sealing inspection report shall be provided to the building owner or owner’s authorized agent and the code official at the time of the framing or insulation inspection. The report shall identify deficiencies found during the review of the construction documents and inspection and details of corrective measures taken.

As stated in the excerpt above, the construction docs will be reviewed by a qualified inspector. These building plans should meet the guidelines established in  the amended rules. Furthermore, the actual construction should follow the construction plans.

It is key to conduct the exterior inspection while the barrier can still be accessed. That way, if any deficiencies are noted, they can be adjusted or repaired efficiently. It would be a much more difficult task to make any air barrier changes after the exterior siding is installed!

A guide in the IRC (labeled as Table N1102.4.1.1) provides an in-depth breakdown of all components of the home, and how each of them should be configured in order to meet code requirements.

Meeting Air Barrier Code Requirements

When it comes to this code, the overall concept is simple – a continuous thermal envelope. or air barrier must be constructed around the house. Any breaks or joints in the air barrier material must be sealed by a code-approved material. Also, the insulation material used for the air barrier cannot be air permeable.

As mentioned above,  Table N1102.4.1.1 provides an extensive explanation regarding each component of the house. So if you want the nitty gritty details, go take a look a the table. But for the sake of this article, we will give you a brief overview:

• Ceilings/Attics – Inspectors will want any access points to unconditioned attics to be sealed with the proper air barrier materials. Additionally, any dropped ceilings or soffits should be outfitted with an air barrier that is aligned with the insulation.
• Walls – Any junctions from sill plate to foundation or top plate to exterior walls must be properly sealed. Additionally, if your attic has knee walls, they must be sealed.
• Windows/Skylights/Doors – All the framing of these penetrations needs to be properly sealed.
• Rim Joists – Exterior air barriers must extend over any rim joists.
• Floors – Any exposed edges of floor insulation must be reinforced by an air barrier. This also applies to cantilevered floors and floors above garages.
• Basements/Crawl Spaces/Slab Foundations – Exposed earth in unvented crawl spaces must be covered with the proper air or vapor barrier. Penetrations in foundation walls and slabs need to be sealed properly.
• Shafts/Penetrations – Ducts, shafts, or penetrations to the exterior or unconditioned spaces must be sealed with approved materials.
• Narrow Cavities – Any cavities too narrow to hold insulation need to be air sealed.
• Garage – Air sealing is needed between the garage and conditioned spaces.
• Recessed Lighting – Lighting fixtures present within the thermal envelope of the building must be properly air sealed.
• Wiring/Plumbing/Other Obstructions – Any breaks in the thermal envelope caused by wiring, plumbing etc. need to be sealed.
• Showers/Tubs – The air barrier installed adjacent to tubs or showers must separate the exterior wall from the tub/shower.
• Electrical or Phone Boxes – Air barriers must be installed under exterior electrical or phone boxes. Air sealed boxes can also be installed as an alternative.
• HVAC Register Boots – HVAC supply/return register boots that penetrate the thermal envelope need to be air sealed.
• Concealed Sprinklers – Concealed fire sprinklers must be sealed, where necessary, according to manufacturer’s recommended method.

Air Barrier Inspections

At Scott Home Inspection, we offer all the Energy Services you’ll need to make sure your building project is up to code. As a qualified third party inspection firm in Larimer County, we have a team of specialists that can inspect and document the exterior of the house to ensure that the building envelope is sufficiently configured.

Additionally, we are also certified to perform blower door, air leakage testing in Larimer County. Due to its adoption of the IECC Residential Energy Codes, Larimer County has required this type of testing in new builds for several years.

By conducting blower door tests, our energy specialists are able to not only determine the energy efficiency of the home, but also identify the sources of air leakage. That way you can make the necessary repairs, as needed, and continue to progress through your building process without a hitch.

We are proud to offer a whole list of specialized Energy Services to Larimer County. We have been providing the region with some of our milestone services such as blower door tests, insulation inspection, and duct leakage testing for years. And now we are ready to take on the newly mandated air barrier inspections with the same professionalism, expertise and efficiency.

If you are in need of an air barrier inspection (or any inspection service for that matter) for your building project, please don’t hesitate to reach out to Scott Home Inspection today! Click here for more info, or click here to schedule your service.