This is how to avoid ventilated shafts.
ASHRAE’s recent update in 2025 introduces a key change: under certain conditions, developers using flammable refrigerant (such as A2L) may not need to run piping through a rated shaft.
The Challenge
With the shift in the use of refrigerants now well underway, developers are adjusting designs to comply with fire and safety codes. What is often overlooked, however, is a critical implication of this change: current codes require refrigerant piping containing flammable refrigerants to be routed through ventilated, rated shafts. This requirement has introduced design and cost challenges for many projects, especially in multi-story buildings where space and layout flexibility are already at a premium.
The Solution
Fortunately, there’s good news. The recent ASHRAE update offers a more flexible approach to refrigerant piping compliance, potentially reducing both complexity and cost in your next development project. Here is the highlight:
ASHRAE 15-2024, Addendum A
- Section 9.12.1.5.1 (with newly added exception d) states:
A shaft enclosure shall not be required for the refrigerant piping if any of the following conditions are met:
- a. Systems using R-718 (water) refrigerant
- b. Systems meeting ASHRAE 34 concentration limits
- c. Piping located on the exterior of the building
- d. Continuous refrigerant piping tested per Section 9.13
In short: You may be able to eliminate the shaft altogether.
Ready to Find Out If Your Project Qualifies?
Let us review your project and save you from unnecessary expenses.
Thank you,
Blair Hildahl
BASE4 Principal
608.304.5228
BlairH@base-4.com
Source:
1.ASHRAE 15-2024 Addendum A – Section 9.12.1.5.1 (Shaft Alternative)
2.ASHRAE 15-2024 – Section 9.13 (Leak testing + pressure integrity)
3.IMC 2021 – General shaft and mechanical enclosure requirements
4.ASHRAE 34 – Concentration tables for refrigerant classification
