A new law in Colorado focusing on environmental standards is set to take effect in January 2026, requiring all residential structures three stories or lower to use Energy Star-rated products. House Bill 23-1161 applies to a range of appliances, fixtures and other products used in residential buildings—including doors, windows and skylights. The new law mandates the use of fenestration products that are Energy Star-rated for the Northern climate zone, despite the fact that parts of Colorado are in the North-Central climate zone. It also marks a juxtaposition of rule for a state in which building and energy codes are adopted at the local level, suggests Kathy Krafka Harkema, U.S. technical operations director for the Fenestration & Glazing Industry Alliance.

“Energy Star is not a code,” Krafka Harkema says. “This is a far-reaching, precedence-setting law that acts like a code.”

Introduced in Colorado’s House of Representatives in February 2023, by a total of 30 representatives and 10 senators, House Bill 23-1161 was passed under strong democratic partisan, commanding 38 votes to two. The bill was passed by the house and the senate in May of this year, after which it was signed into law by Colorado’s governor June 1.

Meanwhile, with Energy Star Version 7.0 set to take effect in October 2023, the new law is a tall order, suggests one Colorado dealer—especially considering the challenges associated with high-performance insulating glass units (IGUs) in high altitude areas.

Most wood and clad-wood windows are manufactured at an elevation of 1,000 feet or less, mainly due to where the source lumber for manufacturing is located, says Gwénaël Hagan, president of Signature Windows + Doors in Denver. At the same time, “Most IGUs are manufactured at lower elevations closer to sea level,” says [DWM] columnist and insulating glass (IG) expert Dave Cooper, of Fenestration Consulting Services LLC. “Then they either get shipped to a higher elevation for installation in a window product or are installed at a lower elevation with the whole product being shipped up to, say, Denver.”

Meanwhile, just 1.2% of the U.S. population lives at or above 5,000 feet of altitude—75% of which is in Colorado’s Front Range communities, Hagan says.

To prevent bowing in IGUs shipped to those higher altitudes, a breather or capillary tube is installed through the edge seal system, Cooper says, adding, “However, this means Argon cannot be used, as it will leak out … affecting the overall U-factor performance.” There are work arounds, he says, “but keeping the Argon between the glass is the goal.”

Due to these altitude-related challenges, “Glass manufacturers do not have an economically viable interest in developing ways to work around altitude issues for such a small segment of the U.S. market,” Hagan suggests. Typical IGUs formulated for the performance requirements of Energy Star’s Northern climate zone can experience issues, such as bowing, glass breakage or unit failure, he says. “… the best U-value bang for [the] buck is the dual-pane, Argon-filled unit with a room-side i-89 low-E coating,” Hagan suggests. “However, that only provides a U-value of 0.26,” which doesn’t meet Energy Star 7.0 requirements. This creates a dilemma for homeowners in the Front Range market, Hagan says. “Most code officials that I have spoken with don’t understand the high-altitude market dynamics and it is clear the lawmakers, lobbyists and industry groups representatives involved in the creation of this law don’t either,” he alleges. “Energy Star 7.0 door values are manageable. However … we don’t sell a window that will hit a 0.22. U-value. Given the small sliver of the U.S. market living at altitude, I don’t see glazing technology coming to the rescue. So it will be up to industry participants to provide the data to state lawmakers to undo the unintended consequences of this well-meaning legislation.”

So far as how Colorado will enforce its new law, state officials plan to do so by monitoring major retailers and distributors via spot checks.

“They’re going to do a lot of mystery shopping of dealers and retailers,” Krafka Harkema said. “So just be prepared … This is coming. It’s law, not proposed legislation. We all need to take a closer look at how we do business in Colorado.”

On or before Jan. 1, 2025, a process will be established through which individuals can anonymously report potential violations. Following investigation, any possible violators will be reported to the state’s attorney general, after which the attorney general may bring civil action and seek civil penalties.

“Colorado is setting up a complaint hotline on their website where you can anonymously report and the fine is $2,000 per violation,” Krafka Harkema said. “So, if you have a house with 50 windows … add that up.”

The new law does provide exceptions for residential doors and windows that are custom-made for historically designated buildings—most notably in cases where they must maintain character.


  1. […] Colorado has discovered a new way to generate revenue from window and door remodeling retailers.  I'm sure everyone in the window and door retail sector is just thrilled about it.Starting in January 2026, a new law regarding environmental standards will be implemented in Colorado. This law will require all residential structures that are three stories or lower to use Energy Star-rated products. House Bill 23-1161 applies to a variety of appliances, fixtures, and products used in residential buildings, including doors, windows, and skylights. Even though parts of Colorado are located in the North-Central climate zone, the new law mandates the use of Energy Star-rated fenestration products for the Northern climate zone. This law represents a change in the state's approach to building and energy codes, which have traditionally been adopted at the local level. Kathy Krafka Harkema, the U.S. technical operations director for the Fenestration & Glazing Industry Alliance, notes that this marks a significant shift in policy.In order to enforce the new law, Colorado officials have planned to conduct spot checks on major retailers and distributors through mystery shopping. This law, which is not just a proposed legislation, requires responsible business owners to thoroughly review their operations to ensure compliance. To report potential violations, individuals can make anonymous reports on the state's website. These reports will then be processed and violators will be reported to the attorney general. If found in violation, civil action may be taken, with civil penalties being sought. The complaint hotline is specifically set up for anonymous reporting, and each violation carries a fine of $2,000. It is important to note that exceptions are provided for custom-made residential doors and windows for historically designated buildings, in order to maintain their unique character.Read the full article at: dwmmag.com  […]

  2. Actually Colorado’s new law DOES allow windows meeting the North-central levels and DOES allow windows with U-factors of up to 0.26. ENERGY STAR v7.0’s Northern criteria has prescriptive levels but also allows “Equivalent Energy Performance” levels — one of which is a U-factor of 0.25 and SHGC of ≥0.40 (conveniently the same as North-central) and another which is a U-factor of 0.26 and again a SHGC of ≥0.40. Builders and window installers are not limited to 0.22 U-factors unless they want to be.

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