International Energy Conservation Code

The International Energy Conservation Code (IECC), formerly known as the Model Energy Code (MEC), is a voluntary code that sets energy-efficiency standards for furnaces, air conditioners, win­dows, and insulation for commercial and residential construction. The Model Energy Code (MEC) was developed jointly by Building Officials and Code Administrators International, Inc. (BOCA), the International Conference of Building Officials (ICBO), the National Conference of States on Building Codes and Standards (NCSBCS), and Southern Building Code Conference International, Inc. (SBC – CI), under a contract funded by the United States Department of Energy (DOE). First published in 1983, subsequent full editions of the MEC were published in 1986, 1989, 1992, 1993, and 1995.

The MEC was first referenced in the National Affordable Housing Act of 1990, and then in the Energy Policy Act (EPAct) of 1992. EPAct was signed into law by President Bush in 1992 and referenced the 1992 MEC as the energy-efficiency standard to be used for new residential construction. Additionally, EPAct required federal mortgage lenders to ensure that homes using their products also comply with the 1992 MEC as a minimum standard. Subsequently, the DOE determined that the 1993 MEC and later the 1995 MEC provided greater energy efficiency for residential buildings and required states to consider adopting the later ver­sion. In concurrence with EPAct, the U. S. Department of Housing and Urban Development (HUD) required compliance with the 1992 MEC as part of its minimum property standards. HUD currently has a final rule pending to upgrade its minimum property stan­dards to the 1995 MEC level. Whether a state has adopted it or not, the MEC applies to houses financed through the Federal Housing Administration (FHA), the Department of Veterans Affairs (VA), and the Rural Economic and Community Development (RECD, for­merly Farmers’ Home Administration). Loans received from or guaranteed by these agencies require that the financed house com­ply with the MEC.

The International Code Council (ICC) was formed in late 1994 by BOCA, ICBO, and SBCCI with the objective of developing a com­prehensive set of U. S. model building codes, known as the International Building Code (IBC). The IBC is a synthesis of the building codes of the three regional model code organizations. These are BOCAs National Building Code, SBCCTs Standard Building Code, and ICBO’s Uniform Building Code.

The MEC had been maintained until 1998 as an activity of the Council of American Building Officials (CABO) and incorporated by reference in each of the three regional model building codes: BOCAs National Building Code (in Chap. 13), SBCCTs Standard Building Code (in an appendix), and ICBO’s Uniform Building Code (in an appendix). The ICC has assumed responsibility from the CABO for maintenance of the CABO One – and Two-Family Dwelling Code and the Model Energy Code to provide proper inter­faces with the international codes. States will have a time window in which to adopt the new ICC model codes.

The 1998 version of the MEC was published as the first International Energy Conservation Code (IECC). The current 2000 IECC addresses the design of energy-efficient building envelopes and the installation of energy-efficient mechanical, lighting, and power systems through requirements emphasizing performance. This comprehensive code establishes minimum regulations for energy-efficient buildings using prescriptive and performance- related provisions. It makes possible the use of new materials and innovative techniques that conserve energy. This second edition incorporates the provisions of the 1998 IECC and its approved changes. Preliminary review of the 2000 IECC seems to indicate that it is more “user-friendly.”

The International Residential Code (IRC), released in 2000, replaces the CABO One – and Two-Family Dwelling Code. A chapter in the IRC addresses energy efficiency but looks significantly dif­ferent from the IECC. Intended to be a simplified prescriptive approach to achieving equivalent compliance with the “perfor­mance” requirements of the IECC, the IRC energy chapter is a table of prescriptive insulation and window requirements.

Most states have adopted some version of the MEC. In states that do not have a statewide energy code, the MEC has also been adopted by individual counties and cities. With continuously changing regulations, as well as the introduction of the IRC in 2000, the status of most states will most likely change. It is impor­tant to check with the local building officials or the state energy office for current requirements.

Most states have adopted a version of the MEC or a similar equivalent energy code. Only six states, Arizona, Illinois, Louisiana, Missouri, South Dakota, Hawaii, and Texas, do not have any statewide mandatory energy codes for low-rise residential con­struction.2 (Hawaii and Louisiana have statewide mandated codes for low-rise multifamily construction.)

Currently, the 1992 MEC has been adopted by Indiana, Iowa, Kentucky, New Mexico, and Tennessee, whereas the 1993 MEC has been adopted by Delaware, Kansas, Montana, and North Dakota. States that have adopted the 1995 MEC are as follows: Connecticut, Georgia, Maryland, Massachusetts, Ohio, Oklahoma, Rhode Island, South Carolina, Utah, Virginia, and Washington, D. C. Nevada still enforces the 1986 MEC, whereas Nebraska uses the 1983 MEC.2

Alabama, Alaska, Arkansas, California, Florida, Minnesota, New York, North Carolina, Oregon, Vermont, Washington, and Wisconsin have adopted a state-developed code that exceeds or meets MEC requirements, whereas Colorado, Idaho, and Maine have adopted a state-developed code that is less stringent than the MEC. Mississippi, New Hampshire, and Wyoming still reference ASHRAE 90-1975, whereas Michigan, New Jersey, and West Virginia reference ASHRAE 90A-1980. Pennsylvania has officially adopted the IECC as a state-mandated energy code.2


The IECC and the MEC allow designers a variety of calculation methods to comply with code requirements. The prescriptive approach, the simplest of the three approaches, allows builders or designers to select from various combinations of energy-conserva­tion measures based on “climate zone” location. Each combination or “package” specifies insulation levels, glazing areas, glazing U – values (thermal performance), and sometimes heating and cooling equipment efficiency. By locating the correct climate zone and look­ing up the appropriate table of packages, builders and officials can ensure that their projects meet or exceed one of the packages list­ed for that zone.3 Few calculations are required.

The tradeoff worksheet approach enables builders to vary insu­lation levels in the ceilings, walls, floors, basement walls, slab edges, and crawl spaces; glazing and door areas; and glazing and door U-values. Based on the proposed plans and specifications, the builder enters simple information on a worksheet and then hand – calculates a total U-value for the project. By comparing the pro­ject’s U-value with the value required for the climate zone, the builder can determine if the project passes the energy code require­ments. The impact of this approach is that as window area increas­es, the thermal performance of the windows must be improved (lowering U-value) or the insulation must be increased in the opaque portion (raising the R-value) in order to satisfy the overall U-value requirement. If the project does not pass, the builder can use the worksheet to examine a different combination of insulation levels, window or door products, and areas for compliance. The worksheet is suitable for use during the plan check and field inspection phases of a project.3

Simplified software products that allow tradeoffs and demon­strate compliance may offer the best combination of simplicity and flexibility. The software approach does the same calculations as the tradeoff worksheet but automates the procedure using a computer. Special features allow builders to trade off heating and air-condi­tioning equipment efficiency, as well as windows and insulation. The software generates a report that is suitable for plan checking and field inspection.3 The “rules” for the assumptions or standard conditions to be used when performing such analyses have been revised substantially in the IECC over those in the MEC.1 Finally, many state energy code offices also provide quantitative R-value standards for the specific locale in order to simplify residential design energy calculations. It is important to consult with local building officials to determine which energy code has been adopted and the calculation methods available.

In addition to the insulation and window requirements, there are basic criteria that must be met regardless of which envelope compli­ance approach is used. These include the following: sealing the build­ing envelope to restrict air leakage (caulking, sealing, and weatherstripping at all penetrations and joints); installing vapor retarders in most climates; identifying materials used for energy code compliance (such as insulation R-values) on plans, specifications, and/or directly on materials in the residence; and insulating and seal­ing ducts in unconditioned spaces as well as insulating pipes for hydronic heating and circulating hot water systems. Tightly sealed structures also can prevent the proper exchange of the minimum ven­tilation needed for the physiologic needs of people. Makeup air, usu­ally through a means of mechanical ventilation, can be implemented to guarantee the proper number of air changes in a home.