Air Barrier Inspections in Larimer County, Colorado

Date Published: November 15, 2022

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.

air barrier

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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!

The air barrier of a newly constructed home.

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.
Builder installing a zip system house wrap

Builder installing a Zip System house wrap. Image sourced from:

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.

A Scott Home Inspection air leakage specialist conducting a blower door test.

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.

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About the Author: Chris Kimmel

Chris Kimmel worked as an Associate Home Inspector for two years, handling numerous services including sewer scope inspections, pest inspections, mold air sample testing, radon testing, and water quality testing. Chris now works with Scott Home Inspection as a Content Writing Specialist.

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