IECC insights

• The International Energy Conservation Code (IECC) is a model building code that provides minimum design and construction requirements for energy efficiency.
• This article identifies and examines the connections between IECC, ASHRAE 90.1 and ASHRAE 90.4.

Since 2000, when the International Energy Conservation Code (IECC) was first published by the International Code Council (ICC), it has been updated every three years to incorporate new technologies and provide energy efficiency guidance and conformance requirements for new building types.

From the beginning, IECC incorporated ASHRAE Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings to define minimum energy efficiency standards requirements for building components (lighting, glazing , roofing, insulation, etc.), service water heating and and power and cooling systems. As ASHRAE Standard 90.1 has evolved, the IECC has also progressed to encompass new building methods and advancements.

Directly referencing ASHRAE Standard 90.4: Energy Standard for Data Centers exemplifies how IECC has progressed in demonstrating energy efficiency compliance for data centers.

The IECC is a model building code that provides minimum design and construction requirements for energy efficiency. It aims to reduce energy consumption in residential and commercial buildings by setting minimum energy performance standards:

1. Building envelope: An efficient building envelope, comprised of exterior walls, roofs, windows, doors is designed to minimize heat loss/gain, solar load and and air infiltration.
2. Heating, ventilation and air conditioning (HVAC): HVAC systems are the greatest energy consumers in a commercial building. A significant portion of the IECC is dedicated to meeting minimum energy efficiency standards.
3. Lighting: The IECC’s lighting efficiency requirements, along with natural lighting and controls, requirements ensure the optimal mix of lighting quality and energy use. Natural lighting and control systems will also reduce energy use.
4. Lighting compliance paths: Depending on the building type and construction, the IECC includes various methods for demonstrating compliance with the stated requirements. These include prescriptive and paths, performance-based paths and and the use of approved software tools.

Figure 1: If a governmental agency or authority having jurisdiction (AHJ) wants to adopt a model code, it will enact an ordinance, regulation or law and incorporate the model code by reference. Courtesy: Bill Kosik, WSP

The IECC has a three-year review cycle and is updated to incorporate the latest design and construction technologies, including the latest building energy efficiency research. State governments and local municipalities can adopt the IECC in whole or in part. Local municipalities often adopt the IECC with modifications that reflect specific climate and energy efficiency goals.

How the content of the IECC is determined

The process of developing/revising the language in IECC is done in an international forum consisting of design and construction professionals, equipment manufacturers, building science experts and and others from the code enforcement community. The forum aims to review proposed changes that improve safety, performance and and technological advances in construction techniques and products.

The discussions are transparent and follow openness, due process and and balance principles. The ICC has a detailed process for voting on code changes, starting with proposal submissions, committee hearings, public comments and hearings, government consensus votes and validation/publication. The number of the ICC voting representatives is based on population and is defined in the ICC bylaws.

Applying the IECC to state and municipal governments

Building codes are part of a state’s compiled statutes (law or agency enforcement) and include state-specific requirements that must be followed under the law or per a state agency. Instead of developing and maintaining a custom code, a state will adopt a model building code, reducing the cost and complexity of enforcing requirements. Using a model code also reduces efforts when updating new technologies and safety protocols. But this is not a one-size-fits-all solution — there are different methods of how the states and municipalities adopt codes:

• State-level adoption: In some states, building codes are adopted at the state level. Local municipalities must strictly follow the language and intent of the state codes.
• State codes with local amendments: States adopt building codes at the state level but with built-in flexibility for allow municipalities to make amendments to address local conditions.
• Local adoption: Building code adoption is left entirely to local jurisdictions. This method can result in differences or contradictions between the local jurisdiction and state regulations (see Figure 1).

How is ASHRAE 90.1 applied within the IECC framework?

ASHRAE 90.1 is the de facto standard for energy efficiency in buildings. It is a “code-ready” standard, meaning local jurisdictions can tailor it and use it as their energy code. The standard has been around since 1975 and has been adopted in the U.S. and around the globe.

Figure 2: This shows the ASHRAE Standard 90.1 savings, year over year. Courtesy: Pacific Northwest National Laboratories, DataHub

In 2009, ASHRAE 90.1 was mandated to be used by federal agencies as the minimum energy efficiency requirement for new federal buildings (see Figure 2).

According to the Building Codes Assistance Project, 38 states have adopted ASHRAE 90.1. International energy standards — very close in content and scope to Standard 90.1 — are also used in India, Canada, Mexico, Dubai, Singapore, Ireland, Hong Kong and other locations.

Finally, in addition to being a template for municipal and state codes, Standard 90.1 is integral to the ANSI/ASHRAE/ICC/USGBC/IES International Green Construction Code Standard (IgCC). While there are differences between Standards 189.1 and 90.1, many provisions in the IgCC are taken directly from or based on ASHRAE 90.1.  Also, Green Building Initiative’s Green Globes and the U.S. Green Building Council LEED use ASHRAE 90.1 as the basis for demonstrating minimum energy efficiency compliance.

ASHRAE 90.4 as an alternate compliance path

Diving deeper into ASHRAE 90.1, Chapter 6 contains a section on “alternate compliance paths” for HVAC systems. An alternate compliance path is used to demonstrate regulatory or certification requirements using a nonstandard approach. Using this method provides an opportunity to work with the local permitting officials and reach a consensus on the viability of the approach.

However, using an alternate compliance path still requires meeting prescriptive requirements for building components such as building envelope and lighting.

An example of this is found in Section 6.6.1 of Standard 90.1. This section provides guidance for an optional path called “Computer Room Systems Path” and allows for the use of ASHRAE 90.4 for computer rooms that have an information technology equipment (ITE) load greater than 10 kilowatts (kW). This provides an advantage to the engineer because ASHRAE 90.4 is written solely for data centers and contains specific methods and language.

Using ASHRAE 90.1 as an alternate compliance path in the IECC

The 2024 edition of IECC includes an introductory note indicating that Chapter 4 provides options for complying with the energy efficiency provisions, including a performance alternative for designs that do not use the prescriptive method.

Figure 3: In addition to changing the compliance process in ASHRAE 90.4 from 2016 to 2022, the mechanical load component (MLC) values are more stringent across all climate zones. ASHRAE acknowledged that the MLC values in the 2016 edition needed to be lowered to ensure reasonable energy efficiency. Courtesy: Bill Kosik, WSP

Section C401.2 indicates that commercial buildings shall comply with:

• 2.1 — IECC (prescriptive path or using building energy use simulation), or
• 2.2 — follow the requirements on ASHRAE 90.1 (as the alternative compliance path).

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