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 five stories or greater in height. Each set of provisions is divided into five different parts:

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

AFUE Annual fuel utilization efficiency
bhp Brake horsepower (fans)
Btu British thermal unit
Btu/h-ft2 Btu per hour per square foot
C-factor See Chapter 2‒Definitions
CDD Cooling degree days
cfm Cubic feet per minute
cfm/ft2 Cubic feet per minute per square foot
ci Continuous insulation
COP Coefficient of performance
DCV Demand control ventilation
°C Degrees Celsius
°F Degrees Fahrenheit
DWHR Drain water heat recovery
DX Direct expansion
Ec Combustion efficiency
Ev Ventilation efficiency
Et Thermal efficiency
EER Energy efficiency ratio
EF Energy factor
ERI Energy Rating index
F-factor See Chapter 2‒Definitions
FDD Fault detection and diagnostics
FEG Fan efficiency grade
FL Full load
ft2 Square foot
gpm Gallons per minute
HDD Heating degree days
hp Horsepower
HSPF Heating seasonal performance factor
HVAC Heating, ventilating and air conditioning
IEER Integrated energy efficiency ratio
IPLV Integrated Part Load Value
Kg/m2 Kilograms per square meter
kW Kilowatt
LPD Light power density (lighting power allowance)
L/s Liters per second
Ls Liner system
m2 square meters
MERV Minimum efficiency reporting value
NAECA National Appliance Energy Conservation Act
NPLV Nonstandard Part Load Value
Pa Pascal
PF Projection factor
pcf Pounds per cubic foot
psf Pounds per square foot
PTAC Packaged terminal air conditioner
PTHP Packaged terminal heat pump
R-value See Chapter 2‒Definitions
SCOP Sensible coefficient of performance
SEER Seasonal energy efficiency ratio
SHGC Solar Heat Gain Coefficient
SPVAC Single packaged vertical air conditioner
SPVHP Single packaged vertical heat pump
SRI Solar reflectance index
SWHF Service water heat recovery factor
U-factor See Chapter 2‒Definitions
VAV Variable air volume
VRF Variable refrigerant flow
VT Visible transmittance
W Watts
w.c. Water column
w.g. Water gauge