The International Energy Conservation Code (IECC) is a model code that regulates minimum energy conservation requirements for new buildings. The IECC addresses energy conservation requirements for all aspects of energy uses in both commercial and residential construction, including heating and ventilating, lighting, water heating, and power usage for appliances and building systems.

    The IECC is a design document. For example, before one constructs a building, the designer must determine the minimum insulation R-values and fenestration U-factors for the building exterior envelope. Depending on whether the building is for residential use or for commercial use, the IECC sets forth minimum requirements for exterior envelope insulation, window and door U-factors and SHGC ratings, duct insulation, lighting and power efficiency, and water distribution insulation.

    Arrangement and Format of the 2015 IECC

    The IECC contains two separate sets of provisions—one for commercial buildings and one for residential buildings. Each set of provisions is applied separately to buildings within their scope. The IECC—Commercial Provisions apply to all buildings except for residential buildings three stories or less in height. The IECC—Residential Provisions apply to detached one- and two-family dwellings and multiple single-family dwellings as well as Group R-2, R-3 and R-4 buildings three stories or less in height. These scopes are based on the definitions of “Commercial building” and “Residential building,” respectively, in Chapter 2 of each set of provisions. Note that the IECC—Commercial Provisions therefore contain provisions for residential buildings four stories or greater in height. Each set of provisions is divided into five different parts:

    1-2Administration and definitions
    3Climate zones and general materials requirements
    4Energy efficiency requirements
    5Existing buildings
    6Referenced standards

    The following is a chapter-by-chapter synopsis of the scope and intent of the provisions of the International Energy Conservation Code and applies to both the commercial and residential energy provisions:

    Chapter 1 Scope and Administration. This chapter contains provisions for the application, enforcement and administration of subsequent requirements of the code. In addition to establishing the scope of the code, Chapter 1 identifies which buildings and structures come under its purview. Chapter 1 is largely concerned with maintaining “due process of law” in enforcing the energy conservation criteria contained in the body of this code. Only through careful observation of the administrative provisions can the code official reasonably expect to demonstrate that “equal protection under the law” has been provided.

    Chapter 2 Definitions. Chapter 2 is the repository of the definitions of terms used in the body of the code. Codes are technical documents and every word, term and punctuation mark can impact the meaning of the code text and the intended results. The code often uses terms that have a unique meaning in the code and the code meaning can differ substantially from the ordinarily understood meaning of the term as used outside of the code.

    The terms defined in Chapter 2 are deemed to be of prime importance in establishing the meaning and intent of the code text. The user of the code should be familiar with and consult this chapter because the definitions are essential to the correct interpretation of the code and the user may not be aware that a term is defined.

    Additional definitions regarding climate zones are found in Tables 301.3(1) and (2). These are not listed in Chapter 2.

    Where understanding of a term’s definition is especially key to or necessary for understanding of a particular code provision, the term is shown in italics wherever it appears in the code. This is true only for those terms that have a meaning that is unique to the code. In other words, the generally understood meaning of a term or phrase might not be sufficient or consistent with the meaning prescribed by the code; therefore, it is essential that the code-defined meaning be known.

    Guidance regarding tense, gender and plurality of defined terms as well as guidance regarding terms not defined in this code is provided.

    Chapter 3 General Requirements. Chapter 3 specifies the climate zones that will serve to establish the exterior design conditions. In addition, Chapter 3 provides interior design conditions that are used as a basis for assumptions in heating and cooling load calculations, and provides basic material requirements for insulation materials and fenestration materials.

    Climate has a major impact on the energy use of most buildings. The code establishes many requirements such as wall and roof insulation R-values, window and door thermal transmittance requirement (U-factors) as well as provisions that affect the mechanical systems based upon the climate where the building is located. This chapter contains information that will be used to properly assign the building location into the correct climate zone and is used as the basis for establishing requirements or elimination of requirements.

    Chapter 4 Energy Efficiency. Chapter 4 of each set of provisions contains the technical requirements for energy efficiency.

    Commercial Energy Efficiency. Chapter 4 of the IECC—Commercial Provisions contains the energy-efficiency-related requirements for the design and construction of most types of commercial buildings and residential buildings greater than three stories in height above grade. Residential buildings, townhouses and garden apartments three stories or less in height are covered in the IECC—Residential Provisions. This chapter defines requirements for the portions of the building and building systems that impact energy use in new commercial construction and new residential construction greater than three stories in height, and promotes the effective use of energy. The provisions within the chapter promote energy efficiency in the building envelope, the heating and cooling system and the service water heating system of the building.

    Residential Energy Efficiency. Chapter 4 of the IECC—Residential Provisions contains the energy-efficiency-related requirements for the design and construction of residential buildings regulated under this code. It should be noted that the definition of a residential building in this code is unique for this code. In this code, a residential building is a detached one- and two-family dwelling and multiple single-family dwellings as well as R-2, R-3 or R-4 buildings three stories or less in height. All other buildings, including residential buildings greater than three stories in height, are regulated by the energy conservation requirements in the IECC—Commercial Provisions. The applicable portions of a residential building must comply with the provisions within this chapter for energy efficiency. This chapter defines requirements for the portions of the building and building systems that impact energy use in new residential construction and promotes the effective use of energy. The provisions within the chapter promote energy efficiency in the building envelope, the heating and cooling system and the service water heating system of the building.

    Chapter 5 Existing Buildings. Chapter 5 of each set of provisions contains the technical energy efficiency requirements for existing buildings. Chapter 5 provisions address the maintenance of buildings in compliance with the code as well as how additions, alterations, repairs and changes of occupancy need to be addressed from the standpoint of energy efficiency. Specific provisions are provided for historic buildings.

    Chapter 6 Referenced Standards. The code contains numerous references to standards that are used to regulate materials and methods of construction. Chapter 6 contains a comprehensive list of all standards that are referenced in the code. The standards are part of the code to the extent of the reference to the standard. Compliance with the referenced standard is necessary for compliance with this code. By providing specifically adopted standards, the construction and installation requirements necessary for compliance with the code can be readily determined. The basis for code compliance is, therefore, established and available on an equal basis to the code official, contractor, designer and owner.

    Chapter 6 is organized in a manner that makes it easy to locate specific standards. It lists all of the referenced standards, alphabetically, by acronym of the promulgating agency of the standard. Each agency’s standards are then listed in either alphabetical or numeric order based upon the standard identification. The list also contains the title of the standard; the edition (date) of the standard referenced; any addenda included as part of the ICC adoption; and the section or sections of this code that reference the standard.

    Abbreviations and Notations

    The following is a list of common abbreviations and units of measurement used in this code. Some of the abbreviations are for terms defined in Chapter 2. Others are terms used in various tables and text of the code.

    AFUEAnnual fuel utilization efficiency
    bhpBrake horsepower (fans)
    BtuBritish thermal unit
    Btu/h-ft2Btu per hour per square foot
    C-factorSee Chapter 2—Definitions
    CDDCooling degree days
    cfmCubic feet per minute
    cfm/ft2Cubic feet per minute per square foot
    ciContinuous insulation
    COPCoefficient of performance
    DCVDemand control ventilation
    °CDegrees Celsius
    °FDegrees Fahrenheit
    DWHRDrain water heat recovery
    DXDirect expansion
    EcCombustion efficiency
    EvVentilation efficiency
    EtThermal efficiency
    EEREnergy efficiency ratio
    EFEnergy factor
    ERIEnergy Rating index
    F-factorSee Chapter 2—Definitions
    FDDFault detection and diagnostics
    FEGFan efficiency grade
    FLFull load
    ft2Square foot
    gpmGallons per minute
    HDDHeating degree days
    HSPFHeating seasonal performance factor
    HVACHeating, ventilating and air conditioning
    IEERIntegrated energy efficiency ratio
    IPLVIntegrated Part Load Value
    Kg/m2Kilograms per square meter
    LPDLight power density (lighting power allowance)
    L/sLiters per second
    LsLiner system
    m2square meters
    MERVMinimum efficiency reporting value
    NAECANational Appliance Energy Conservation Act
    NPLVNonstandard Part Load Value
    PFProjection factor
    pcfPounds per cubic foot
    psfPounds per square foot
    PTACPackaged terminal air conditioner
    PTHPPackaged terminal heat pump
    R-valueSee Chapter 2—Definitions
    SCOPSensible coefficient of performance
    SEERSeasonal energy efficiency ratio
    SHGCSolar Heat Gain Coefficient
    SPVACSingle packaged vertical air conditioner
    SPVHPSingle packaged vertical heat pump
    SRISolar reflectance index
    SWHFService water heat recovery factor
    U-factorSee Chapter 2—Definitions
    VAVVariable air volume
    VRFVariable refrigerant flow
    VTVisible transmittance
    w.c.Water column
    w.g.Water gauge