The 2018 North Carolina Energy Conservation Code, which had a compliance date of Jan. 1, 2019, includes a number of changes impacting residential building envelope requirements. The most important changes were prescriptive insulation improvements, duct leakage improvements, and addition of the Energy Rating Index (ERI) compliance path option.

The new ERI option for builders includes the mandatory minimum insulation levels of the previous North Carolina Energy Code (the 2012 North Carolina Energy Conservation Code). The mandatory requirements of sections R401 through R404 still need to be met when using the ERI compliance path. 

Overview of North Carolina’s Residential Envelope Changes

  • R-values and U-factors have been improved for wood framed walls, ceilings, below-grade walls, and crawl space walls. 
  • Requirements for total duct leakage and duct leakage to the outside have been improved. 
  • Maximum ERI scores with and without calculation of on-site renewable energy, have been specified for climate zones 3, 4, and 5.

What is the Energy Rating Index?

The ERI provides a new path for energy code compliance. Builders using this path need to achieve a certain score, on a scale from 0 to 100, to achieve energy efficiency code compliance for building construction. The score of 100 aligns with the 2006 IECC model code. A lower score means a more energy efficient home.

In North Carolina, the target ERI score, through Dec. 31, 2022, is 65 in Climate Zone 3, and 67 in Climate Zones 4 and 5, and RESNET-accredited software is used to calculate the ERI score.

While the ERI is a performance path approach, it also carries certain mandatory elements. For example, if a builder uses the ERI path, the insulation levels must still meet or exceed the prescriptive levels found in the 2012 North Carolina Energy Conservation Code.

There are two distinctions for builders using the ERI path:

  • The ERI path is distinct from the Home Energy Rating System (HERS index scale) since other approved home rating programs could, in theory, be used for ERI compliance.
  • Both HERS and ERI allow for the use of renewable energy to reduce scores, however, ERI includes provisions to ensure that renewable energy does not replace more permanent or reliable energy efficiency measures. As a matter of practice, the ERI path calls for builders to use HERS to demonstrate building code compliance. Therefore, if the ERI path is used for energy code compliance and renewable energy is incorporated, builders must meet more stringent ERI targets.

To view a listing of the key residential envelope changes in the North Carolina Energy Conservation Code, download the detailed summary.

This summary is offered for informational purposes only. It does not purport to be an exhaustive analysis of code changes or provide advice that will ensure guaranteed compliance with any energy code provision. Please consult with local authorities before finalizing your installation plans.

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