Local Stretch Codes Explained

Last updated: April 2026

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Quick Answer

The 2024 International Energy Conservation Code (IECC) is the most adopted energy code in the U.S. and is updated every 3 years.
The U.S. Department of Energy determined the 2024 IECC achieves 7.8% site energy savings and 6.6% energy cost savings compared to the 2021 IECC.
Residential provisions in the 2024 IECC offer more flexibility for builders to achieve compliance.
Local jurisdictions like Colorado and Utah have adopted the IECC 2024, sometimes with amendments.

The 2024 International Energy Conservation Code (IECC) represents a significant step forward in building energy efficiency across the United States. This model building code, developed by the International Code Council (ICC) and first created in 2000, serves as the foundation for many state and local energy regulations. It is recognized as the national model energy code for low-rise residential buildings. The U.S. Department of Energy (DOE) has determined that the 2024 IECC achieves a 7.8% site energy savings and 6.6% energy cost savings when compared to its previous 2021 edition. These improvements mean new construction will be more efficient, leading to lower utility bills and reduced environmental impact. Local jurisdictions often adopt the IECC, sometimes adding their own amendments, which creates what we call "stretch codes." These local codes aim to push energy efficiency even further, beyond the baseline set by the national model.

What is the International Energy Conservation Code (IECC)?

The International Energy Conservation Code (IECC) is a crucial model building code established by the International Code Council (ICC). This code sets minimum efficiency standards for new construction. It covers many parts of a building, including the structure's walls, floors, ceilings, and even the lighting. The IECC also addresses critical areas like windows, doors, duct leakage, and air leakage. These standards ensure that new buildings are constructed to a certain level of energy performance from the start.

The IECC is the most adopted energy code in the country. It serves as a benchmark that many states and cities use for their own building regulations. The code was first created in 2000 and has been updated regularly since then. The updates happen every three years, ensuring the code stays current with new technologies and energy-saving strategies. This regular update cycle helps push the construction industry toward more efficient practices over time. When we refer to the "national model energy code for low-rise residential buildings," we are talking about the IECC. This means it provides the foundational rules for how homes and smaller residential structures should be built to conserve energy.

The Role of the ICC in Code Development

The International Code Council (ICC) plays a central role in developing the IECC. The ICC is a member-focused association dedicated to developing model codes and standards used in the design, build, and compliance process. Their work ensures that buildings are safe, resilient, and sustainable. The IECC is one of their flagship codes, specifically focused on energy conservation. The process of updating the IECC involves extensive research, public input, and committee reviews. Experts from various fields, including builders, engineers, and energy specialists, contribute to shaping the code's requirements. This collaborative approach helps ensure the code is practical, achievable, and effective in promoting energy efficiency.

Setting Minimum Efficiency Standards

The IECC sets minimum efficiency standards, which means it establishes the lowest acceptable level of energy performance for new construction. Builders must meet or exceed these standards. For example, the code specifies certain R-values for insulation in walls and ceilings, U-factors for windows, and air leakage rates for the building envelope. These standards are designed to reduce energy waste. By addressing areas like duct leakage and air leakage, the IECC helps prevent conditioned air from escaping a building. This reduces the amount of energy needed to heat or cool the space. The goal is to create buildings that use less energy for heating, cooling, lighting, and water heating, leading to lower operating costs for homeowners and occupants.

Evolution of the IECC

Since its creation in 2000, the IECC has continuously evolved. Each three-year update introduces new requirements and often tightens existing ones, pushing for greater energy efficiency. The 2024 IECC is the latest iteration, building upon the foundations laid by previous versions like the 2021 IECC. These updates reflect advancements in building science, materials, and construction techniques. They also respond to a growing understanding of the importance of energy conservation and climate change. The consistent evolution of the IECC means that buildings constructed today are significantly more energy-efficient than those built even a decade ago. For HERS Raters and energy code professionals, understanding these updates is very important because the IECC will be the benchmark for many states, counties, and municipalities moving forward Ekotrope's overview of 2024 IECC residential updates. This continuous improvement cycle ensures that the IECC remains relevant and effective in its mission to promote energy-efficient construction practices across the nation.

How Does the 2024 IECC Improve Energy Efficiency?

The 2024 International Energy Conservation Code (IECC) brings significant improvements in energy efficiency compared to its predecessors. It builds on previous editions by making performance targets more challenging while also offering greater flexibility in how those targets can be met. This balance allows builders to innovate and choose the most cost-effective methods for their specific projects. The U.S. Department of Energy (DOE) has officially determined that the 2024 IECC achieves substantial energy savings.

Specifically, the 2024 IECC achieves a 7.8% site energy savings compared to the 2021 IECC. This means new buildings constructed under the 2024 code will consume nearly 8% less energy at the building site itself. Beyond just energy consumption, the DOE also found that the 2024 IECC achieves 6.6% energy cost savings compared to the 2021 IECC. This translates directly into lower utility bills for homeowners and building occupants, making energy-efficient homes more affordable to operate over their lifetime. These savings are a key indicator of the code's effectiveness in promoting genuine energy conservation.

Targeted Efficiency Enhancements

The 2024 IECC introduces several targeted enhancements to improve efficiency. One notable area of change involves ceiling insulation requirements. The prescriptive attic insulation requirements have been reduced by R-11 across all climate zones. This change might seem counterintuitive at first glance, but it is part of a broader, more holistic approach to energy performance. The overall energy performance targets have gotten more challenging, even with this specific change. This indicates that other aspects of the building envelope or systems are being tightened to compensate, or that the code is allowing for greater overall performance flexibility.

For example, the 2024 IECC residential provisions offer substantially more flexibility and a wider range of options for builders to achieve compliance. This means builders are not locked into a single prescriptive path but can choose from various strategies, such as improving window performance, optimizing HVAC systems, or incorporating renewable energy, to meet the overall energy performance target. This approach allows for greater innovation and adaptation to regional building practices and material availability.

The Department of Energy's Determination

The U.S. Department of Energy (DOE) plays a crucial role in evaluating the impact of new energy codes. Their determination on the 2024 IECC provides an authoritative assessment of its energy-saving potential. The DOE's analysis confirmed the 7.8% site energy savings and 6.6% energy cost savings when compared to the 2021 IECC. This determination is important because it provides a quantitative measure of the code's effectiveness. It helps demonstrate to states and local jurisdictions the tangible benefits of adopting the latest IECC edition. The DOE’s findings validate the efforts of the International Code Council and the committees involved in developing the code, showing that their work leads to real-world energy and cost reductions. This rigorous evaluation process ensures that the IECC remains a credible and impactful tool for promoting energy efficiency in new construction.

Balancing Performance and Flexibility

A key characteristic of the 2024 IECC is its emphasis on balancing more challenging performance targets with increased flexibility for builders. While the overall energy performance targets have gotten more stringent, the code provides more pathways to meet these targets. This flexibility is crucial for builders operating in diverse climates and markets. It allows them to choose combinations of measures that are most practical and cost-effective for their specific projects. For instance, a builder might opt for higher-performance windows in one climate zone, while another might focus on enhanced air sealing and efficient HVAC systems in a different zone. This adaptable approach helps ensure that the code can be practically implemented across the country, encouraging wider adoption and compliance.

The flexibility extends to how different components of a building's energy performance interact. Instead of rigid prescriptive requirements for every single element, the 2024 IECC often allows for a performance-based approach. This means that if a builder exceeds the requirement in one area, they might be able to slightly adjust another area, as long as the overall energy performance of the building meets the code's target. This holistic view encourages builders to think about the entire building as an energy system, rather than just isolated components. This approach can lead to more innovative and efficient designs, ultimately benefiting the homeowner with a more comfortable and energy-efficient home.

What are Local Stretch Codes and How Do They Relate to the IECC?

Local stretch codes are energy codes adopted by states, counties, or municipalities that typically go beyond the baseline requirements of a model code like the International Energy Conservation Code (IECC). The IECC provides a strong foundation for many state and city energy codes, but local jurisdictions often choose to amend it or adopt a more stringent version to achieve greater energy efficiency. The 2024 IECC itself includes Appendix RG, which specifically outlines a "2024 IECC Stretch Code" 2024 International Energy Conservation Code. This shows that the concept of a stretch code is formally recognized and supported within the national model.

When local jurisdictions adopt the IECC, they have the option to implement it "with amendments" or "without amendments." Adopting it with amendments means they are adding stricter requirements or different pathways that push energy performance beyond the base IECC. This is where the term "stretch code" often comes into play. For instance, jurisdictions adopting the IECC 2024 include Phoenix, Colorado, Illinois, Nevada, Clark County, Las Vegas, New York State, New York City, North Dakota, Rhode Island, Nashville and Davidson County, Austin, and Utah Energy Code, 2024 (IECC 2024) | UpCodes. Some of these, like Colorado and Utah, have adopted the IECC 2024 with amendments, signaling their intent to implement a stretch code that demands even higher levels of energy efficiency for new construction within their boundaries.

The Purpose of Stretch Codes

The primary purpose of local stretch codes is to accelerate the transition to more energy-efficient and sustainable buildings. While the base IECC provides a solid minimum, many communities have ambitious goals for reducing energy consumption, cutting carbon emissions, and promoting renewable energy. Stretch codes allow these communities to mandate higher standards than the national model, tailoring requirements to their specific climate, resources, and policy objectives. For example, a city committed to achieving net-zero energy buildings by a certain date might implement a stretch code that makes significant strides toward that goal, even before the national code fully catches up. These codes also serve as a way for progressive jurisdictions to lead by example, demonstrating what is possible in energy-efficient construction.

How Jurisdictions Adopt and Amend the IECC

The process of adopting and amending the IECC varies by jurisdiction. Typically, a state, county, or city government will review the latest edition of the IECC. They then decide whether to adopt it as is, or to modify it to better suit local conditions and policy goals. When a jurisdiction adopts the IECC "with amendments," it means they are making specific changes to the code's provisions. These amendments might include requiring higher insulation R-values, lower air leakage rates, mandatory renewable energy installations, or stricter efficiency standards for heating and cooling equipment. For example, some jurisdictions might require all new homes to be "electric-ready" or "solar-ready," even if the base IECC only offers these as optional appendices. The decision to adopt amendments often involves public hearings, stakeholder input, and a legislative or regulatory process to ensure that the new requirements are fair, feasible, and beneficial to the community.

The 2024 IECC Stretch Code Appendix

The inclusion of Appendix RG: 2024 IECC Stretch Code within the 2024 International Energy Conservation Code itself is a notable development. This appendix provides a pre-packaged, more stringent version of the base code, making it easier for jurisdictions to adopt a stretch code without having to draft all the amendments themselves. This resource streamlines the process for local governments that wish to go beyond the minimum requirements. It offers a clear pathway to implementing higher energy performance standards, encouraging communities to aim for greater efficiency. The presence of such an appendix also signals that the ICC recognizes the growing demand for more aggressive energy codes and provides a framework for jurisdictions to meet those demands. By offering a ready-made stretch code option, the IECC supports communities in their efforts to build smarter and more sustainably.

What Key Updates Affect Residential Buildings in the 2024 IECC?

The 2024 International Energy Conservation Code (IECC) brings several important updates that specifically affect residential buildings. These changes aim to boost energy efficiency in homes while also providing builders with more flexible ways to meet the new standards. The goal is to make new homes even more efficient, comfortable, and ready for future energy technologies. The 2024 IECC offers substantially more flexibility and a wider range of options for builders to achieve compliance, according to the NAHB's overview of the 2024 IECC U.S. Department of Energy 2024 IECC determination. This means that instead of a one-size-fits-all approach, builders can tailor their energy-saving strategies to best suit their designs and local conditions.

One of the significant changes involves updates to ceiling insulation requirements. While the overall energy performance targets have become more challenging, the prescriptive attic insulation requirements have been reduced by R-11 across all climate zones. This adjustment reflects a more integrated approach to building envelope design, where improvements in other areas might offset a change in one specific component. The code also addresses important aspects like solar-ready provisions and electric-ready building provisions, ensuring that new residential structures are prepared for renewable energy and electrification trends.

Enhanced Flexibility for Builders

A major theme in the 2024 IECC for residential buildings is increased flexibility. Builders now have more choices in how they achieve the required energy performance. This can involve a mix of strategies, such as improving window U-factors, enhancing wall insulation, reducing air leakage, or installing more efficient heating and cooling systems. This approach allows builders to consider the cost-effectiveness and practicality of different measures in their specific market. For example, a builder might find it more cost-effective to invest in advanced air sealing techniques rather than significantly increasing wall insulation, as long as the overall energy performance target is met. This flexibility is crucial for maximizing design choices and ensuring that the code can be practically implemented in the field.

Solar-Ready Provisions

The 2024 IECC includes Appendix RB: Solar-Ready Provisions for detached one- and two-family dwellings and townhouses. This appendix provides guidelines for making new homes "solar-ready." This means designing and constructing the roof and electrical system in a way that makes it easier and less expensive to install solar panels in the future. Specific requirements might include reserving adequate roof space free of obstructions, ensuring the structural integrity of the roof to support solar arrays, and pre-wiring electrical conduits to the main service panel. By incorporating these provisions, the code encourages homeowners to adopt renewable energy without the significant retrofitting costs that might otherwise be incurred. This forward-thinking approach helps facilitate the widespread adoption of solar power in residential settings.

Electric-Ready Building Provisions

Another forward-looking aspect of the 2024 IECC is its focus on electric-ready residential building provisions. Appendix RK: Electric-Ready Residential Building Provisions outlines requirements for new homes to be prepared for future electrification. This means ensuring that the electrical infrastructure, such as wiring and panel capacity, is sufficient to support electric appliances like heat pump water heaters, induction cooktops, and electric vehicle charging stations. As homes move away from fossil fuels and towards electricity for various functions, having an electric-ready infrastructure minimizes the need for costly electrical upgrades later on. This not only supports energy efficiency but also aligns with broader goals of decarbonization and reducing reliance on natural gas. These provisions make it easier for homeowners to transition to all-electric living, contributing to a more sustainable energy future.

Other Key Residential Appendices

Beyond solar and electric readiness, the 2024 IECC includes other residential appendices that offer additional pathways and considerations for energy efficiency. Appendix RC: Zero Net Energy Residential Building Provisions, for example, provides guidelines for achieving highly efficient homes that produce as much energy as they consume over a year. Appendix RD: Electric Energy Storage Provisions addresses the integration of battery storage systems, allowing homes to store excess renewable energy. Appendix RE: Electric Vehicle Charging Infrastructure outlines requirements for installing EV charging capabilities. Appendix RF: Alternative Building Thermal Envelope Insulation R-Value Options offers different ways to meet insulation targets, providing more choices for builders. Finally, Appendix RH: Operational Carbon Rating and Energy Reporting, and Appendix RI: On-Site Renewable Energy, further emphasize the code's comprehensive approach to energy performance and environmental impact. These appendices provide a rich set of resources and options for builders and jurisdictions aiming for higher levels of sustainability and energy independence in residential construction.

How Does the IECC Intersect with Programs like ENERGY STAR?

Understanding the updates to the International Energy Conservation Code (IECC) is very important for HERS Raters and energy code professionals. This is because the IECC serves as the benchmark for many states, counties, and municipalities moving forward. These professionals need to know the latest code requirements to accurately assess and certify new construction projects. The IECC sets the minimum standards, and many energy efficiency programs, like ENERGY STAR, build upon these minimums, often requiring even higher levels of performance.

The Ekotrope blog, in its overview of the 2024 IECC for residential construction, specifically mentions the intersection of IECC 2024 with key Energy Efficiency initiatives like ENERGY STAR and HUD loan qualifications Ekotrope's overview of 2024 IECC residential updates. This highlights that the IECC is not an isolated set of rules but rather a foundational element within a broader ecosystem of energy efficiency programs and incentives. Achieving compliance with the IECC is often the first step toward qualifying for these advanced programs, which offer additional benefits to builders and homeowners.

ENERGY STAR Residential New Construction Program

The ENERGY STAR Residential New Construction Program is a voluntary program that certifies homes and apartments as energy-efficient. To earn the ENERGY STAR label, a home must meet strict guidelines for energy efficiency set by the U.S. Environmental Protection Agency (EPA) ENERGY STAR Residential New Construction Program. These guidelines typically go beyond the minimum requirements of the IECC. For example, an ENERGY STAR certified home might feature better insulation, more efficient windows, tighter construction for reduced air leakage, and high-efficiency heating, cooling, and water heating systems. The program ensures that certified homes deliver significant energy savings, greater comfort, and improved indoor air quality compared to conventional new homes.

While the IECC sets the base level, the ENERGY STAR program provides a path for builders to achieve a higher tier of energy performance. Builders often use the IECC as their starting point and then implement additional measures to meet the more stringent ENERGY STAR requirements. This synergy means that as the IECC improves, it becomes easier for builders to achieve ENERGY STAR certification, further accelerating the adoption of advanced energy-saving practices. Homeowners buying an ENERGY STAR certified home can be confident that their new home is built to a higher standard of energy efficiency, leading to lower utility bills and a more comfortable living environment Energy Efficient New Homes and Apartments.

HERS Raters and Energy Code Professionals

HERS Raters (Home Energy Rating System Raters) are crucial to both IECC compliance and ENERGY STAR certification. They are trained and certified professionals who inspect and test homes to determine their energy efficiency. For IECC compliance, HERS Raters perform evaluations to ensure that new construction meets the code's prescriptive or performance-based requirements, including conducting blower door tests for air leakage and duct leakage tests. For ENERGY STAR certification, Raters verify that a home meets all the program's specific requirements, often using advanced energy modeling software. Their expertise ensures that homes are built as designed and that energy-saving features are properly installed and functioning. The updates in the 2024 IECC mean that HERS Raters need to stay current with the new performance targets, compliance options, and any changes in measurement or verification protocols.

The Role of HUD Loan Qualifications

The mention of HUD (Department of Housing and Urban Development) loan qualifications in relation to the IECC highlights how energy efficiency can impact financial aspects of homeownership. HUD offers various loan programs, and some of these may have energy efficiency requirements or incentives. For example, certain FHA (Federal Housing Administration) mortgage programs might offer benefits for homes that meet specific energy-efficient criteria. While the direct link isn't fully detailed in the provided research, it suggests that meeting or exceeding IECC standards, and potentially achieving certifications like ENERGY STAR, can positively influence a home's eligibility for certain financing options. This integration of energy efficiency into loan qualifications provides another incentive for builders to construct high-performance homes, making them more attractive and accessible to buyers. It underscores the growing recognition that energy efficiency is not just an environmental concern but also an economic one, affecting both operational costs and financing opportunities for homeowners.

Who Develops the IECC and What is Their Focus?

The International Energy Conservation Code (IECC) is developed by the International Code Council (ICC). This organization is responsible for creating a suite of model building codes that are widely adopted across the United States and in other countries. The ICC's mission includes ensuring public safety, health, and welfare through the development of codes and standards. For the IECC specifically, their focus is on setting minimum efficiency standards in new construction.

The development process for the IECC involves a broad group of stakeholders. Committees are formed to review proposals, debate changes, and ultimately shape the content of each new edition of the code. These committees include representatives from various sectors of the building industry. For instance, the National Association of Home Builders (NAHB) was represented on both committees responsible for developing the 2024 IECC. This representation included a small group of NAHB builder members and NAHB staff. These individuals dedicated significant time and effort to ensure the new energy code would meet specific objectives.

Prioritizing Cost-Effectiveness and Consumer Benefits

One of the key priorities for the committees developing the IECC, as highlighted by the NAHB, is ensuring cost-effectiveness. This means that the energy-saving measures required by the code should provide a reasonable return on investment for builders and homeowners. The goal is to avoid mandating changes that are prohibitively expensive or that do not offer tangible benefits in terms of energy savings and reduced operating costs. Related to this is the focus on consumer benefits. The code aims to create homes that are not only more energy-efficient but also more comfortable, healthier, and ultimately more affordable to live in over the long term. Reduced energy bills and improved indoor air quality are direct benefits to the consumer that the code seeks to deliver.

The NAHB representatives, for example, worked to ensure these aspects were central to the 2024 IECC. They aimed for a code that would provide real value to homeowners without imposing undue financial burdens on the construction process. "Although the 2024 IECC will achieve incrementally higher energy savings than the 2021 edition, the residential provisions will offer substantially more flexibility and a wider range of options for builders to achieve compliance," said NAHB regarding the 2024 International Energy Conservation Code overview. This statement underscores the commitment to both higher energy savings and practical, flexible implementation for the benefit of builders and consumers alike.

Maximizing Design Choices for Builders

Another crucial focus during the development of the IECC is maximizing design choices for builders. The committees strive to create a code that allows for innovation and variety in home design, rather than imposing rigid, restrictive requirements. This is evident in the 2024 IECC's residential provisions, which offer substantially more flexibility and a wider range of options for builders to achieve compliance. This flexibility means that builders can choose from various pathways to meet the energy performance targets, allowing them to adapt to different architectural styles, construction methods, and material availability. By offering multiple compliance options, the code empowers builders to integrate energy efficiency seamlessly into their designs without compromising aesthetic or functional preferences. This approach helps ensure that energy-efficient homes can be built across diverse markets and consumer preferences.

Practical Implementation in the Field

Finally, the committees developing the IECC place a strong emphasis on practical implementation in the field. A code, no matter how well-intentioned, is only effective if it can be realistically applied by builders and enforced by local jurisdictions. This means considering the availability of materials, the skills of the workforce, and the typical construction practices in different regions. The NAHB staff and builder members involved in the 2024 IECC development devoted significant time to ensure the new energy code could be practically implemented. This focus helps avoid requirements that are overly complex, difficult to inspect, or that rely on technologies not yet widely available or affordable. By ensuring the code is practical, the ICC helps facilitate its widespread adoption and successful application, ultimately leading to more energy-efficient buildings across the country. These individuals continue their work on these bodies to develop the next edition of the code, the 2027 IECC, further emphasizing the continuous commitment to practical, effective energy standards.

Frequently Asked Questions

What is the main purpose of the IECC?

The main purpose of the International Energy Conservation Code (IECC) is to set minimum energy efficiency standards for new construction. It ensures that buildings, including their walls, floors, ceilings, lighting, windows, doors, and systems, are designed and built to conserve energy. The IECC aims to reduce energy consumption, lower utility costs for occupants, and promote more sustainable building practices. The code was first created in 2000 and has been the national model for residential buildings since then.

How often is the IECC updated?

The International Energy Conservation Code (IECC) is updated every three years. This regular update cycle ensures that the code remains current with advancements in building science, technology, and energy-saving strategies. Each new edition, such as the 2024 IECC, builds upon the previous one, often introducing more stringent requirements and new compliance options to push for greater energy efficiency across the construction industry.

Which states have adopted the 2024 IECC?

Several states and local jurisdictions have adopted the 2024 IECC, sometimes with amendments. Adopting jurisdictions include Phoenix, Colorado, Illinois, Nevada, Clark County, Las Vegas, New York State, New York City, North Dakota, Rhode Island, Nashville and Davidson County, Austin, and Utah. Colorado and Utah, for example, have adopted the IECC 2024 with amendments, indicating a commitment to even higher energy efficiency standards.

What are some key changes in attic insulation requirements in the 2024 IECC?

One key change in the 2024 IECC for residential buildings is a reduction in prescriptive attic insulation requirements. The prescriptive attic insulation requirements have been reduced by R-11 across all climate zones. While this specific change might seem to lower a standard, it is part of a broader strategy where overall energy performance targets have become more challenging, with increased flexibility in how those targets are met across the entire building envelope and systems.

Does the 2024 IECC include provisions for electric vehicles or solar readiness?

Yes, the 2024 IECC includes several provisions for electric vehicles and solar readiness through its appendices. Appendix RB covers Solar-Ready Provisions for detached one- and two-family dwellings and townhouses, making it easier to install solar panels in the future. Appendix RE addresses Electric Vehicle Charging Infrastructure, and Appendix RK outlines Electric-Ready Residential Building Provisions, preparing homes for future electrification of appliances and vehicle charging.