By Cornelia Wu | Thu, December 18, 25
In 2025, the region showed forward progress and frustrating setbacks in building energy codes. Most states in New England and the Mid-Atlantic are reviewing or adopting the 2024 International Energy Conservation Code (IECC), including appendices and strengthening amendments. We see some momentum behind electric readiness provisions. These prevent costly upgrades for consumers down the line, enabling them to make the choice to adopt modern technologies in the future.
However, some states are facing resistance to forward-looking code elements or even to the recent model codes. The result? A mixed bag of progress and pushback, reflecting the broader national debate around energy and housing affordability. In this post, we provide a state-by-state roundup of regional progress and pushback on energy codes.
Why Building Codes are Good for Affordability and Housing Construction
When energy codes face setbacks, consumers miss opportunities to embrace energy efficiency that helps pocketbooks now and down the road. Improved energy codes support building measures that improve health and safety, and lower energy burden. And they can help – not hinder- new construction.
In October, the American Council for an Energy-Efficient Economy (ACEEE) published an article demonstrating that new home construction rates in states that adopted the 2021 IECC continue in line with national trends. For an analysis of the different factors that contribute to costs and savings as a result of building energy codes, see NEEP’s resource Energy Codes and Affordability.
Despite the benefits of updated codes, the National Association of Home Builders (NAHB) declared that there is a push to “mandate the use of restrictive, costly energy codes that raise housing costs while providing little energy savings to consumers.” These claims look at upfront costs while ignoring life cycle cost analyses.
Many other factors affect housing starts, from interest rates to skilled labor shortages. We need to keep energy codes in the conversation so that new housing construction can proceed at full speed ahead.
Led by Rhode Island, Region Pursues latest Model Codes
Eight states have reviewed or are reviewing the most recent model codes for adoption– the 2024 International Energy Conservation Code (IECC) and/or American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) 90.1-2022. These include Connecticut, the District of Columbia, Delaware, Maine, Maryland, Massachusetts, New Jersey, New York, and Rhode Island.
Rhode Island became the first state in our region with an effective energy code based on the 2024 IECC. Rhode Island published an updated version of its Energy Code, which became effective on December 1, 2025. The update includes Appendices RK and CH, which establish electric-ready provisions for residential and commercial buildings.
Electric readiness provisions in these appendices require that dedicated electrical circuits of the correct voltage and amperage for electric appliances be installed in new construction so that in the future, a consumer can replace fossil fuel appliances with induction cooktops, heat pump clothes dryers, or heat pump water heaters if they choose. Similarly, new commercial buildings are required to provide dedicated infrastructure and designated future locations for all-electric equipment. These requirements are important because they reduce future retrofit costs and preserve owner/resident abilities to make choices.
We’re seeing progress with electric readiness provisions across the region, which have already been incorporated into codes in Maryland and the District of Columbia. Massachusetts and Vermont have incorporated electric readiness provisions into their stretch codes.
Some States Chart Forward Progress but also Backward Steps
New York
New York is another state in our region about to make the 2024 IECC effective. The 2025 Energy Conservation Construction Code of New York State (ECCCNYS), which incorporates the 2024 IECC, ASHRAE 90.1-2022, and strengthening amendments was adopted on July 25, 2025. Important energy efficiency features such as thermal bridge mitigation and enhanced building envelope requirements are included.
Additional all-electric requirements, with some exceptions, would apply to most new buildings seven stories or less starting December 31, 2025, and to the remainder of new construction, with some exceptions, by 2029. The requirements do not apply to existing buildings. In November, New York paused the effective date of 19 N.Y.C.R.R. § 1240.6 (Part 1240.6), the section of the ECCCNYS that governs fossil-fuel equipment and building systems, until litigation challenging the All-Electric Buildings Act is resolved.
Part 1240.6 of the code supports buildings that are designed to be more efficient, resilient, and cost-effective over time while also being practical by providing exemptions to the all-electric requirements. For instance, fossil-fuel equipment could be used for emergency backup or standby power generation, and in manufactured homes, agricultural buildings, critical infrastructure and other applications. Fossil fuel equipment could also be used in cases where a local utility determines that new or expanded electric service cannot be reasonably provided by the utility to ensure that electrification requirements do not outpace grid capacity.
All other components of the 2025 ECCCNYS update go into effect on December 31, 2025.
Delaware
The story of this year’s report-out on Delaware starts 16 years ago, when the state first introduced long-term requirements for energy-efficient construction, with an implementation deadline of December 31, 2025. Over the years, the state established a series of requirements for construction capable of future upgrades to higher levels of energy efficiency. Today, the proposed energy code meets some but not all of these requirements.
In 2009, legislation required that all new residential building construction in Delaware shall be zero net energy capable by December 31, 2025, and that all new commercial building construction shall be zero net energy capable by December 31, 2030. In 2023, legislation mandated electric vehicle capable requirements for both single-family and multifamily residential buildings, and solar ready zone requirements for large commercial buildings.
In July 2025, the Department of Natural Resources and Environmental Control (DNREC) staff proposed regulatory language to incorporate these requirements into an updated State Energy Conservation Code, based on the 2024 IECC with strengthening amendments. The Code included the addition of optional Passive House and Zero Energy Ready Homes compliance paths to meet the residential zero net energy capable requirement. This Code was based on the 2024 IECC plus appendices for EV charging infrastructure and solar ready zones. In October, The Secretary of the DNREC declined to approve the current version of Docket No. 2025-R-CCE-0008/7 (Del. Admin. Code 2101), Regulations for State Energy Conservation Code, and directed DNREC Energy staff to prepare a revised proposal.
On December 1, 2025, DNREC published the revised 2101 Regulations for State Energy Conservation Code and re-opened a period of public comment, with comments due by December 31, 2025. As directed, the Code omits the residential zero net energy capable construction requirement. However, the regulation still enables DNREC to advance a code that satisfies Delaware’s statutory mandates for electric-vehicle-charging and solar-roof readiness.
Vermont
Last year, Vermont adopted the 2024 building energy codes, based on the 2021 IECC and known as the Vermont Residential Building Energy Standards (RBES) and Commercial Building Energy Standards (CBES). The Code became effective July 2024. However, recent actions have rolled back energy efficiency in Vermont’s codes.
On September 17, 2025, Vermont Governor Phil Scott issued Executive Order (EO) No. 06-25 that reinstated the 2020 building energy codes, which are based on the 2018 IECC. Projects can now choose to comply with either the 2020 RBES/CBES (including the 2020 Stretch Code) or the 2024 RBES/CBES. The EO cites complaints from homeowners, builders, and economic development professionals, such as unreasonable compliance costs, insufficient workforce training, and negative impacts on housing affordability. On November 20, the Vermont Attorney General issued a formal Attorney General Opinion (the first since 2014) that states that the EO does not exceed the Governor’s authority to the extent that it directs agencies to commence rulemaking, but that “the Order exceeds the Governor’s authority to the extent it intends to immediately change any law related to wetlands and building energy standards without rulemaking.”
The Department of Public Service (DPS) is required to submit a report, due May 2026, to the Governor that explores the affordability impacts of the RBES and CBES, compliance information for both the 2020 and 2024 codes, recommended modifications for future code updates, and a regional assessment of energy codes across New England and the Mid-Atlantic.
Room for Improvement
On July 1, 2025, the International Codes (Building Code, Residential Code, Fire Code, Mechanical Code, Plumbing Code) in New Hampshire were updated to the 2021 model code version, except for the Energy Code, which remained at the 2018 model code year.
The NH local chapter of ASHRAE formed a working group to evaluate the costs and benefits of updating the state’s energy building code from 2018 to the 2024 IECC and presented the findings to the State Building Code Review Board (BCRB), Quantifying the Cost and Benefits of Upgrading the NH IECC 2018 Building Energy Code to the IECC 2024 Code. The working group assessed the cost implications and the projected energy savings associated with stricter code requirements for construction in New Hampshire. The group, which included a professional cost estimator and engineering professionals from across the state, used a recently designed New Hampshire multi-family building as the reference model. The analysis found that moving from the IECC 2018 building code, including the New Hampshire amendments, to the IECC 2024 code would have a 0.2% impact on the upfront cost to build the structure, and immediately reduce the operating costs of the building by approximately 15%.
Despite the significant benefits of the updated code, the New Hampshire 2024 IECC Committee recommended that the State Building Code Review Board (BCRB) not adopt the 2024 IECC, citing concerns about construction costs and potential impact on housing costs. The BCRB voted to maintain the 2018 IECC. The 2024 IECC Committee did note concerns that remaining on the 2018 IECC could increase long-term complexity, as future update cycles would require evaluating changes across multiple intervening editions of the IECC.
Leading the Nation
Even with the mix of forward and backward movement, the region continues to lead the nation in code adoption. Several states have adopted or are reviewing the 2024 IECC and many have adopted electric readiness provisions, electric vehicle capable requirements, and solar ready roof zones. Beyond 2024 IECC and ASHRAE 90.1-2022 adoptions, states are advancing benchmarking, Building Performance Standards, net zero buildings, and stretch codes. And the next round of model codes is already in the works. The 2025 public comment draft of the 2027 IECC was published in October and is open for public comment through December 15, 2025. Since their introduction, energy codes have been designed to create buildings that are efficient and healthy to live in. Requirements such as better insulation and improved airtightness have enabled homeowners and tenants alike to save on energy bills. With readiness provisions, energy codes are even more forward-thinking, saving building owners from costly future retrofits, and enabling choice further down the road. Stay tuned for an update to our Energy Codes and Affordability resource in 2026.
