Colorado has officially adopted a new building code designed to make homes and offices more climate-friendly without further inflating the state's high cost of living.
The Colorado Energy Office published its Model Low Energy and Carbon Code today, which will become the state’s new minimum building code on July 1, 2026. After that date, all cities and counties must adopt the regulations whenever they update local building codes or adopt even tougher local building efficiency rules.
“Colorado is helping to pave the way for a more affordable cost of living and, at the same time, making significant progress towards reducing greenhouse gas pollution and meeting our climate goals,” said Will Toor, the director of the Colorado Energy Office.
The new minimum requirements are part of a multi-year plan to bring local building codes in line with state climate goals. In 2022, Gov. Jared Polis signed a law to establish the Colorado Energy Code Board to develop statewide building standards, which published an initial set of minimum codes a year later to ensure future buildings were wired for solar panels and electric vehicle chargers.
The latest minimum code takes aim at emissions coming directly from homes and offices. State data show residential and commercial buildings account for almost 10 percent of Colorado's contribution to climate change, making the sector the state’s fifth-largest source of greenhouse gas emissions behind transportation, electricity generation, oil and gas and heavy industry.
Home builders warn the new rules will further increase housing prices across Colorado. Toor, however, said the rules will insulate residents from high energy bills, and that the toughest requirements only apply to large, luxury homes rather than smaller, more affordable units.
What’s in the new building codes
The new building code is a modified version of the 2024 code developed by the International Code Council (IECC), an independent non-profit organization that develops building standards used by state and local governments.
The rules set exacting requirements for everything from the proper depth of nails to the amount of insulation required within walls and ceilings. The IECC updates those requirements every three years, and its 2024 updates made the rules less rigid by providing builders more options to meet energy efficiency standards.
The U.S. Department of Energy determined the standards would generally improve overall energy efficiency. An analysis commissioned by the National Association of Homebuilders also found the 2024 update would reduce the cost of building new homes in most places.
Colorado’s energy code board met for more than a year to trim and tailor the 2024 IECC code. The panel included affordable housing experts, local officials, union leaders, architects, sustainability advocates and a home builder.
The final version sets tougher standards for larger homes. If a home is under 5,000 square feet, it must meet baseline energy efficiency standards. If a home is between 5,000 and 7,499 square feet, it must be even more efficient. If it's over 7,500 square feet, the home must cover its total energy usage with onsite options like solar panels or purchase offsite energy from a community solar garden or another source.
“Extra-large homes generally have an exponential increase in energy use from amenity loads like pools and spas and snow melt systems,” said Adam Berry, a senior advisor for the Colorado Energy Office focused on building codes. “While it's a relatively small number of homes that we're talking about, it's a very large amount of energy.”
Colorado’s updated codes also tweak standards to encourage the adoption of all-electric heat pumps. Those systems work like reversible air conditioners to both heat and cool homes, potentially replacing a natural gas furnace.
Toor said the new rules don’t mandate a shift away from natural gas heating. The standards instead set a single energy efficiency target for all-electric and mixed-fuel buildings so heat pumps can compete with fossil-fuel-based systems on a level playing field.
“There is much more parity between gas and electric than in prior versions of the code,” Toor said.
An ongoing debate over affordability
Colorado home builders, however, expect the rules will increase the cost of much-needed housing.
In a written statement, Ted Leighty, the CEO of the Colorado Association of Home Builders, claimed the code council favored local officials from affluent communities over homebuilders or future home buyers. He added that tougher energy efficiency rules won’t make it any easier for Colorado residents to afford a home.
“Our primary concern, which was largely dismissed by the board and CEO staff, is that housing affordability is determined by whether families and individuals can afford to purchase a home in the first place—not whether their energy bill savings will offset the increased costs of their home decades later,” Leighty said.
In comments submitted to the code council, the home builders pushed the state to adopt the 2024 IECC without modifications. The trade association warned that additional rules would restrict the housing supply by making Colorado more competitive for home builders than neighboring states.
Meanwhile, the new codes won praise from environmental advocates like Christine Brinker, a buildings policy expert with the Boulder-based Southwest Energy Efficiency Project.
“It’s the right code for Colorado. In a nutshell, it has the right balance between energy efficiency and affordability,” Brinker said.
