Idaho Energy Code Overview: Residential

Idaho's current residential energy code, effective January 2015, is based on the 2012 International Energy Conservation Code (IECC) with state-specific amendments that drop its stringency to that of the 2009 IECC. Full versions of the IECC are available on the International Code Council's website. Amendments to Idaho's residential energy code can be found in the 2018 Idaho Statutes and Administrative Rules.

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Residential Energy Code

The residential energy code applies to new construction, as well as additions, alterations, renovations, and repairs.

Residential buildings include one- and two-family homes and townhouses of any size; apartments, boarding houses, dormitories, and other buildings with two (2) or more permanent dwelling units; and residential care and assisted living facilities with three (3) or less stories, among others. 

Any nonconditioned space that is altered to become conditioned space, such as heating an unfinished basement, must also fully comply with the code. 

Code Provisions

The residential energy code has provisions pertaining to a home's thermal envelope, mechanical system, and lighting system. Mandatory requirements are included for:

2012 International Energy Conservation Code Climate Zone Map

2012 International Energy Conservation Code Climate Zone Map

  • Infiltration control

  • Duct insulation, sealing, and testing

  • HVAC controls

  • Piping insulation

  • Equipment sizing

  • Dampers

  • Lighting

Some requirements vary by climate zone, including those for:

  • Roofs

  • Above grade walls

  • Foundations (basements, slabs, crawlspaces)

  • Fenestration (skylights, windows, doors)

Idaho has jurisdictions in climate zones 5 and 6. 

Compliance Options

There are three options for complying with the residential energy code: prescriptive, total UA alternative, and performance.

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  • Sections R401-R404

  • Mandatory provisions must be met

  • No trade-offs permitted

  • No software tools needed

Total UA Alternative

  • Section R402.1.4

  • Mandatory provisions must be met

  • U-factor and assembly area used to determine trade off

  • REScheck or approved method


  • Section R405

  • Mandatory provisions must be met

  • Simulated energy performance analysis comparing annual energy cost

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Code Specific Questions

For questions about specific code requirements, visit the resource page, check the Frequently Asked Questions, or contact us