The U.S. Environmental Protection Agency (EPA) today published a final rule that will allow the continued installation in new homes of HVAC units manufactured or imported prior to Jan. 1, 2025, that use R-410A refrigerant until existing supplies of these HVAC units are depleted.

The rule becomes effective on July 27, 2026.

The HVAC industry is transitioning to new refrigerants required by the American Innovation and Manufacturing (AIM) Act of 2020, which gradually phases down the use of existing classes of refrigerants and establishes new requirements for the refrigerants used in air conditioners and heat pumps. The new class of refrigerants, commonly referred to as A2Ls, has a lower global warming potential (GWP) than older ones.

For more information on the new refrigerants, read this explainer post from NAHB staff.

The new refrigerants were not compatible with existing systems at the time. Manufacturers had to design new units to accommodate the A2Ls. EPA then laid out a timeline for the transition to the new units and for a phase-down in the manufacture of the older refrigerants.

Prior to EPA’s amended rule, contractors and builders were not allowed to install after Jan. 1, 2026, any split HVAC system manufactured before Jan. 1, 2025, that used refrigerant with a higher GWP such as R-410A. Late last year, EPA noted that enforcement of that deadline would be deprioritized in response to concerns on the availability and cost of A2L refrigerant in the field. To address these implementation challenges, EPA proposed changes last fall to the final rule.

Now, existing HVAC equipment using R-410A refrigerant can continue to be installed under EPA’s amended final rule. There are no new complete R-410A HVAC systems being manufactured so the supply of these units will eventually run out. But manufacturers are still producing components for the older systems for maintenance purposes.

Home builders, remodelers and developers can still procure and install HVAC systems using R-410A refrigerants until supply of existing units is exhausted. It should be noted that R-410A is being gradually phased out on a schedule that will decrease its production year-by-year until it reaches 15% of current output by 2036. This will impact supply of R-410A used for maintenance going forward.

Home builders also need to check state and local laws before installing the older systems. New York has passed a statewide law codifying the original Jan. 1, 2026 deadline, meaning no R-410A systems can be installed in New York.

For products that do not require field assembly, such as window air conditioning units, the rules establish the final date of sale as three years after the manufacture compliance date, no later than Jan. 1, 2028, without a compliance date for installation.