What is the International Energy Conservation Code®?

The IECC® is a model energy building code produced by the International Code Council® (ICC®). It is referred to as a “model” code because it was developed through a public hearing process by national experts under the direction of the ICC.

States and local jurisdictions most often look to national model energy codes as the starting point for their own codes. Simply adopting model energy codes makes it easier for them to keep current with the most recent building practices and technology. The IECC is updated on a three year cycle, with the most recent being the 2012 IECC. While states may adopt any building code they like, most states adopt a version of the IECC either with or without amendments. The Building Codes Assistance Project tracks state code adoption and allows for quick comparison of code requirements across states through their code status maps.

What are the Requirements of the IECC?

The IECC sets minimum energy efficiency provisions for both residential and commercial buildings. Users of the code can choose between two methods for showing compliance, the prescriptive and performance paths.

The prescriptive path of the code sets specific minimum performance levels for each of the components of the building envelope, such as ceiling and wall insulation, window U-factor and solar heat gain coefficient (SHGC), and air infiltration. For each component, these prescriptive requirements must be met or exceeded, without the ability to tradeoff between components. While it allows less flexibility, this path can be more straightforward to comply with.

In the performance path, users can have performance of components that are lower in one area, as long as they make up for it with higher performance in another area. Energy calculations are used to determine if the tradeoffs are equivalent. In some cases, additional requirements necessitate the use of the performance path; for instance, if a commercial building wants to exceed 40% window to wall area, it must use the performance path.

These links provide more information about each version of the code, as well as tables of some of the key requirements of the prescriptive path of the code:


IECC 2006


IECC 2009


IECC 2012

What is covered by the IECC?

The IECC covers new construction, additions, remodeling, window replacement, and repairs of specified buildings. The residential portion of the code applies to buildings that are detached one- and two-family dwellings and buildings that contain three or more dwelling units and are three stories or less in height above grade. The commercial portion of the code applies to all non-residential buildings and to multifamily buildings over three stories in height.

The code provisions are intended to ensure the design of energy efficient building envelopes. They also address the energy efficiency of elements that do not affect the building envelope, such as mechanical, water heating, electrical, and lighting equipment. The envelope requirements focus on insulation requirements for ceilings, walls, and floors and on thermal conductance of windows and doors.

Climate Zones

The Code requirements vary by region. The regions are determined based on the climate and, hence, are called "climate zones." Each county in the country is sorted into one of eight climate zones and sub-categorized based on climate type (moist, dry and marine). The map below shows how the climate zones apply across the United States.

IECC Climate Zone Map