Energy Code Adoption Toolkit


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The Colorado Energy Office (CEO) created an Energy Code Adoption Toolkit to assist Colorado jurisdictions through the process of energy code adoption. The toolkit provides information on the benefits of adopting a more current energy code, and gives tips on how to navigate the typical adoption process. It also includes several resources that:

  • Detail the costs of updating an energy code
  • Describe changes made in the latest version of the International Energy Conservation Code (IECC)
  • Provide example language for the adoption of stretch codes that go beyond the IECC
  • Help jurisdictions verify code compliance 

The resources in this Energy Code Adoption Toolkit are designed to put all of the necessary code adoption information in one place, while walking jurisdictions through the process. If you can't find your answer in these resources, you can submit a question to our Code Helpline and our subject matter experts will respond to you via email within three business days.

When adopting building codes, the Chief Building Official (CBO) often discusses the update with various stakeholders, including the City Council, the Board of County Commissioners, and the local building community, among others. This section provides talking points for the CBO when having these discussions, in order to advocate for the adoption of a more current energy code that will benefit their community.

Lower Insurance Rates for Jurisdictions

The Building Code Effectiveness Grading Schedule (BCEGS) program could lead to a lower insurance rate by assigning a jurisdiction a classification from 1 (exemplary commitment to fire and building code enforcement) to 10 (not committed). This is similar to the Public Protection Classification program that is in place for fire protection, but the BCEGS program is based on building code enforcement. The assigned classification takes into account what current fire and building codes are in place, the retention of the code’s structural provisions, code official qualifications, and public awareness programs. In other words, if your jurisdiction elects to adopt the latest energy code, your jurisdiction may receive a discounted insurance rate. For more information, visit the ISO Mitigation website.

Energy Cost Savings

Any measure that is enacted in each new version of the IECC must show energy cost savings. This means that most buildings are able to see a return on investment in only a few years through the savings acquired through their energy bills. See the Cost Impacts of Updating Energy Codes section of this toolkit for a summary of cost savings by IECC version.

The U.S. Department of Energy has issued residential and commercial analyses showing that residential buildings meeting the 2021 IECC, compared to those meeting the 2018 IECC, would result in energy cost savings of approximately 8.66 percent, while commercial buildings would result in energy cost savings of 10.6 percent.


The International Code Council created a building codes Resilience Toolkit that provides resources aimed at helping jurisdictions plan, prepare for, and successfully recover from and adapt to adverse events. ICC notes that "resilience starts with strong, regularly updated, and properly implemented building codes."

As the IECC continues to develop through each code cycle, homes and buildings are becoming more resilient as they incorporate newer materials, techniques and technologies that come to market. Buildings are being better built with an improved ability to endure severe weather and changes in the atmosphere, including storms, moisture, temperature swings, and more. With these advancements also come increased durability, safety, and comfort for occupants who may need to shelter in place during these weather events. In its 2019 Natural Hazard Mitigation Saves report, the National Institute of Building Sciences found that adopting the 2018 International codes has a benefit-cost ratio of $11 for every $1 spent. Building codes are an extremely cost-effective strategy for making a community's built environment safer and more resilient to natural and man-made hazards.

Contribution to Local Climate Action Plans

Many jurisdictions have adopted Climate Action Plans (CAP) to meet community goals related to greenhouse gas emissions reductions and resilience.  These plans often outline an emission inventory, detailing where emissions are generated in the community. Building energy consumption is consistently a large contributor to local emissions, and therefore building energy codes are a key strategy for communities to meet the goals in their CAP.  CAPs may be the responsibility of another department such as Planning or Sustainability.  Coordinating with this department and discussing how an energy code update could contribute to community CAP goals could create additional support for the code update.

Consistency for Designers and Builders

Colorado is a home rule state, which grants jurisdictions local control over which building and energy code is adopted (though Colorado state statute requires jurisdictions to adopt  the 2021 IECC and the Colorado model electric ready and solar ready code upon adopting or updating any other building code). Since designers and builders work in multiple jurisdictions, a consistent code reduces their time and cost of designing and building to different code requirements. For production builders, it also means they don’t have to customize standard designs to comply with each jurisdiction's code. Adopting the same code requirements as neighboring jurisdictions also helps designers and builders become more familiar with consistent code requirements, likely reducing plan check correction comments or inspection items.

Available Training and Software

Did you know that the Colorado Energy Office offers free training on the latest energy codes? By adopting a more recent energy code, there are many more resources to train building code officials that are often at no expense to your jurisdiction. It's also important to note that the U.S. Department of Energy only supports the most recent energy code editions in the REScheckTM and COMcheckTM software that is used for determining compliance.

CEO-sponsored recorded webinar IECC trainings are available on CEO's YouTube Channel.

Flexibility for Homebuilders

In the 2015 IECC, a new compliance path was added for residential applications called the Energy Rating Index path (ERI). This compliance path was improved upon in the 2018 IECC. Builders who choose to use the ERI obtain a score ranging from 0 to 100, where zero represents a net zero energy home and a score of 100 represents a home built to the 2006 IECC. Each point in the scale represents a one percent change in the relative energy efficiency of the home; lower ERI scores equate to improved efficiency. The ERI compliance path can make it easier for both homebuilders to comply with code and for plan examiners to verify compliance.

Staying Up to Date with Building Code Adoption

In 2022, the Colorado General Assembly passed HB22-1362, which requires local jurisdictions to adopt the 2021 IECC and the Colorado model electric ready and solar ready code upon updating or adopting any other building code. Jurisdictions can adopt codes on their own schedule, but must meet the state minimum requirements when undergoing any code update.

CEO recommends adopting the corresponding edition of the IECC as part of a jurisdiction’s entire package of building codes. The I-Codes are written to be adopted together and that limits conflicts between the IECC and other building codes like the International Building Code, the Residential Code and the International Mechanical Code.

CEO has put together visual guides of typical energy code adoption and compliance processes.  Processes may vary by jurisdiction but these guides give a generic view of the steps necessary to adopt and comply with an energy code, and who is typically involved to do so. Guides include:

  • Adoption Process Map - this map outlines the typical code adoption process and compliance process.
  • IECC Adoption Implementation Plan - CEO developed this plan to help jurisdictions implement a new version of the energy code in phases and achieve improved building compliance and understanding.

The best way to stay up to date on what is changing in the I-Codes is by joining a committee to develop the code. How can you get involved in the code development process? Throughout each code cycle there are calls for committees related to the code development process. For more information, see the ICC's call for committees.

Subscribe to these newsletters for code updates:

Scaling Multiple Code Cycles at Once

It can be daunting to move from an older edition of the IECC to a newer one, especially when skipping several code versions. CEO offers free technical assistance for jurisdictions adopting the latest energy code to help through this process. The assistance can be customized to a jurisdiction’s needs and used to help work through the adoption process. To request technical assistance, please fill out this short form: Technical Assistance Request.

2018 to 2021: There were several changes to the 2021 IECC that aim to make buildings nearly 10% more efficient than the previous code. We created a Residential Significant Changes Guide and a Commercial Significant Changes Guide to help jurisdictions and the building industry learn and navigate the changes. We also created Code Comparison tables from the 2009 IECC through the 2021 IECC for Residential and Commercial.

2015 to 2018: There are minimal changes between the 2015 IECC and the 2018 IECC. This document provides an easy-to-follow guide on the significant changes for both the residential and commercial codes. For residential, the largest changes are within lighting, thermal envelope and the Energy Rating Index. Major changes in the commercial code include lighting, additional efficiency package options and thermal envelope. 

There are multiple sources of upfront costs to consider when updating to a newer code. For a jurisdiction, the costs of code books, training, outreach, publishing notices and the added construction costs must be accounted for at a minimum. As new codes are adopted, the update also may require more staff to enforce provisions correctly unless the new code requirements can fit into what the jurisdiction’s staff is already implementing. It's also worth noting however, the building codes are an extremely cost-effective approach to making your community's built environment more resilient to natural and man-made hazards.

Accounting for Costs to Your Jurisdiction

  1. View these Residential and Commercial Code Comparison documents to see how the code has changed from the 2009 IECC to the 2021. These documents can be used to estimate the impact each measure has on your jurisdiction’s code adoption plan and decide if your jurisdiction needs more staff to implement these code changes properly.
  2. Find out how much your jurisdiction spends on books. Free online versions of the I-codes are available on ICC's website for the 2021 IECC and the 2018 IECC. An estimate of how much it is to purchase a set of hard copies for all of the I-codes can cost upwards of $1,000.
  3. Look for free training opportunities provided by the Colorado Energy Office, Xcel Energy or other local groups to offset the cost of training your staff.
  4. Account for marketing costs to update website information and to send publishing notices.

Construction Costs

The initial design and construction decisions determine what the operational and maintenance costs will be for the building and therefore, it's important to look at when a building can start to see a return on investment. The National Association of Home Builders (NAHB) published an “Estimated Cost of the 2018 IRC Code Changes” research paper that found that adopting the 2018 codes actually decreases residential construction costs for Colorado’s climate zones when compared to building to the 2015 codes. NAHB also published a 2021 Residential Cost Effectiveness Analysis which found that updating to the 2021 IECC from the 2018 IECC ranges in construction cost from $8,695 to $11,900 for homes depending on the efficiency package selected for climate zone 5.

Furthermore, in May 2019, the U.S. Department of Energy published a study, "Preliminary Energy Savings Analysis: 2018 IECC Residential Requirements" which found that in Colorado's climate zones, homes built to the 2018 IECC will save approximately 2 percent in annual energy costs. Then in 2021, the DOE published another study, “Analysis Regarding Energy Efficiency Improvements in the 2021 International Energy Conservation Code” and determined that homes built to the 2021 IECC will save approximately 8.66% in energy cost savings when compared to the 2018 IECC.

Residential cost information for updating to 2021 IECC
Commercial cost data for updating to 2021 IECC


Stretch or reach codes refer to adding code requirements that go above and beyond the base code, which is in most instances a version of the IECC. Below we’ve provided a few examples of codes that incorporate advanced design and technology practices.

Building Decarbonization Code

In 2021, New Buildings Institute (NBI) released its Building Decarbonization Code, version 1.2. Local and state governments can overlay the language in this code with the 2021 IECC to deliver carbon neutral performance for new construction. Version 1.2 is now compatible with ASHRAE 90.1. According to NBI, the Building Decarbonization Code is designed to help states and cities working to mitigate carbon resulting from energy use in the built environment, which accounts for 39% of U.S. emissions. The Code covers both residential and commercial construction and is structured to present both all-electric new construction, and electric-ready options for jurisdictions in different stages of decarbonizing their building stock.

In 2020, NBI also published a white paper, "Energy Code Roadmap for Getting to Zero Outcomes," that describes a process by which jurisdictions can incrementally strengthen building performance standards through codes over time in order to decarbonize the building sector.

Colorado Model Electric Ready and Solar Ready Code

The Colorado Energy Code Board published the Colorado model electric ready and solar ready code on June 1, 2023. This code includes provisions for both residential and commercial buildings on electric readiness, solar readiness, and EV readiness. This code is required for adoption any time a jurisdiction updates or adopts any building code after July 1, 2023.

Zero Energy Appendix

The Zero Energy Appendix provides requirements for buildings intended to result in net zero energy consumption over the course of a year. 

ZERH (Zero Energy Ready Homes)

A U.S. Department of Energy (DOE) Zero Energy Ready Home (ZERH) is a home that meets all of the criteria found in the DOE ZERH National Program Requirements. DOE ZERH are verified by a qualified third party and are at least 40% to 50% more energy efficient than a typical new home. This generally corresponds to a Home Energy Rating System (HERS) Index Score in the low 50s, depending on the size of the home and region in which it is built. All DOE ZERH are so efficient that the addition of an onsite renewable energy system can offset most or all of the home’s annual energy consumption.

All-Electric New Construction

As the electrical grid decarbonizes due to an increasing supply of renewable energy generation, municipalities and counties looking for ways to further reduce greenhouse gas emissions from burning fossil fuels have adopted ordinances or building codes that require newly constructed buildings to be all-electric. There are currently more than 40 jurisdictions in California that have passed all-electric new construction mandates, in addition to dozens of cities across the U.S. that are considering such a move. Building beneficial electrification involves installing energy-efficient electric equipment—such as heat pumps for space heating and cooling, heat pump water heaters, and induction cooktops—in place of combustion-fueled (typically propane or natural gas) equipment. Benefits of electrification include better indoor air quality, safety from gas leaks, savings from no first costs of natural gas infrastructure installation, as well as fewer emissions from a cleaner electrical grid.

SWEEP's report, Building Electrification: How Cities and Counties are Implementing Electrification Policies (July 2020) provides case studies from a dozen local governments on how they adopted code language to advance beneficial electrification.

International Green Construction Code (IgCC)

The IgCC provides a comprehensive set of requirements intended to reduce the negative impact of buildings on the natural environment. It is a document which can be used readily by manufacturers, design professionals and contractors. What sets it apart in the world of green building is that it was created with the intent to be administered by code officials and adopted by governmental units at any level as a tool to drive green building. With that said, unless your jurisdiction has the staff to enforce the entire IgCC, then it may be worth looking through the IgCC and only adopting sections that align with your community’s goals to start. The IgCC covers a variety of topics, including indoor air quality, energy, water, waste, materials, operation and more.

High Performance Energy Codes around the Country

In addition to stretch codes implemented in Colorado, below are some examples of stretch codes or custom codes being used elsewhere that could be used for inspiration.

International Wildland-Urban Interface Code (IWUIC)

The unrestricted use of property in wildland-urban interface areas is a potential threat to life and property from fire and resulting erosion. The IWUIC is a model code that can be adopted by a jurisdiction in addition to their building and fire codes. The objective of the code is to establish minimum special regulations to safeguard life and property from wildfires and to prevent structures from spreading to wildland fuels, even in the absence of fire department intervention.

Do you have a question about the building I-codes, how to review or inspect for a measure, how the I-codes interact, or how to comply? We can help! If you're in Colorado, you can submit a question to our free Code Helpline. Our subject matter experts will respond to you via email within two business days. 

We’ve compiled the following resources to support the code compliance process. 

SolarAPP+ – The National Renewable Energy Laboratory has launched a collaborative effort with key code officials, authorities having jurisdiction, and the solar industry to develop standardized plan review software that can run compliance checks and process building permit approvals for eligible rooftop solar systems. SolarAPP+ integrates with existing government software to provide automated plan review, permit approval, and project tracking in an effort to reduce the workload on permitting offices. SolarAPP+ is free for city and county permitting offices.  

CEO developed an IECC Adoption Implementation Plan to help jurisdictions implement a new version of the energy code in phases and achieve improved building compliance and understanding.

Troubleshooting Code Interpretation Guide - This guide provides explanations for some commonly-asked questions on how the 2018 IECC interacts with the other I-codes and how to interpret mechanical, electrical, envelope and additional efficiency package code measures. It also provides clarification on compliance and enforcement roadblocks that multiple jurisdictions across the state of Colorado have encountered.

Plans Examiner Checklists

Building Inspector

Commissioning Checklists:

REScheckTM and COMcheckTM Support and Guides

Guides for verification of Manuals J, D, S and N are provided on ACCA’s website or follow these cheat sheets:

Energy Ratings: ERI vs. HERS Fact Sheet

Do you have a question about the building I-codes, how to review or inspect for a measure, how the I-codes interact, or how to comply? We can help! If you're in Colorado, you can submit a question to our free Code Helpline. Our subject matter experts will respond to you via email within two business days. 

Click on the links below or visit our YouTube channel to view recorded video presentations for each training webinar. Slide presentations are available where noted.

Short Training Videos

IECC 2021 General Training

IECC 2021 Residential Trainings

IECC 2021 Commercial Trainings

Commercial Model Electric Ready and Solar Ready Code Training

General Topics (applicable to 2018 or 2021 IECC)

Zero Energy Ready Home (ZERH) Training Series 
The Colorado Energy Office sponsored a Department of Energy ZERH Program Webinar Training Series in Spring 2020.

  1. ZERH Intro to Building Science
  2. ZERH Program Overview
  3. ENERGY STAR, the Foundation of the ZERH Program
  4. Indoor airPLUS and the ZERH Program
  5. Additional ZERH Program Requirements
  6. Cold Climate Building Science and Assemblies

Recorded webinar trainings for the City and County of Denver can be found on Denver's Building Department site under Building Guides, and IECC Training Sessions 

Technical Analyses:

Energy Savings Analysis: 2021 IECC for Residential Buildings (July 2021)

DOE has issued a final determination that the 2021 International Energy Conservation Code (IECC) will improve energy efficiency in residential buildings. DOE analysis indicates that buildings meeting the 2021 IECC, as compared with buildings meeting the 2018 IECC, would result in national site energy savings of 9.38 percent, source energy savings of 8.79 percent, and energy cost savings of approximately 8.66 percent of residential building energy consumption.

Cost-Effectiveness of the 2021 IECC for Residential Buildings in Colorado - 2015 IECC baseline (Dec 2021) 

Do you have a question about the building I-codes, how to review or inspect for a measure, how the I-codes interact, or how to comply? We can help! If you're in Colorado, you can submit a question to our free Code Helpline. Our subject matter experts will respond to you via email within two business days. In addition to the helpline, we also created two resources as listed below:

  • Energy Code Fact Sheet for Homeowners: Provides guidance to homeowners who are rebuilding following the Marshall Fire in Superior, Louisville, and unincorporated Boulder County, Colorado
  • Builder and Homeowner Quick Reference Guide: Building Efficient and Resilient Homes Quick Reference Guide: Covers the top building energy and water saving options for a builder or homebuyer to consider when renovating or building a new home

Additionally, the following is a list of websites that provide helpful resources for energy code adoption and compliance: