PERFORMANCE: Codes & Standards

International Energy Conservation Code (IECC)

In many states and local jurisdictions, the International Energy Conservation Code (IECC) serves as the energy efficiency baseline for residential and commercial construction, additions and major renovations. The commercial chapter of the IECC sets energy efficiency requirements for non-residential buildings and for residential buildings with more than three stories. As a compliance alternative, this chapter references ASHRAE Standard 90.1.

Fenestration in new construction and additions as well as new fenestration in existing buildings is among the systems covered by the IECC. The choice among three compliance options determines the requirements for fenestration and other building systems:

  • Prescriptive path. The most straightforward compliance option. Building components, such as fenestration, must meet prescriptive energy efficiency requirements. This compliance option limits the allowable window-to-wall area and skylight-to-roof area.
  • Total building performance path. Provides design flexibility, allowing any building design to comply as long as the overall simulated energy budget does not exceed the budget of a reference design that would meet the prescriptive requirements. This method requires detailed modeling that takes into account performance factors such as the impact of fenestration properties on daylighting potential and passive solar heating.

Fenestration Energy Ratings
Regardless of the chosen compliance path, the following fenestration energy properties are critical for compliance with the code: U-factor, solar heat gain coefficient (SHGC), air leakage, and possibly visible transmittance. These properties must be provided as certified ratings determined by independent laboratories in accordance with National Fenestration Ratings Council (NFRC) standards. Air leakage ratings can also be based on the North American Fenestration Standard. A recent method for generating certified NFRC ratings for commercial fenestration is the Component Modeling Approach (CMA).

Versions of the IECC
The first International Energy Conservation Code was published in 1998. A new version of this model code is published in its entirety every 3 years. The most current version is the 2018 IECC, although most state and local codes are still based on older IECC versions (see the Building Codes Assistance Project for code status by state). The links below provide overviews of the prescriptive fenestration requirements of different IECC versions:

2018 International Energy Conservation Code »

2012 International Energy Conservation Code »

2009 International Energy Conservation Code »

2006 International Energy Conservation Code »


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