Permitting Modification of Shaft Requirements for Refrigerant Piping in the 2021 & 2024 International Mechanical Code
Originally Published by Greg Johnson on Linked in - Original Link Here
There is a significant problem with the shaft requirements of the 2021 and 2024 IMC for refrigerant piping which - according to the original proponent - unintentionally codified a provision that requires ventilated and drained shafts for Group A2L refrigerants, regardless of the quantity of refrigerant in the piping.
The cost burden of providing these unnecessary shafts is considerable; a client in the multifamily design industry tells us that some developers estimate $250K to provide these shafts in a 300 unit multifamily building.
The following article documents the rationale for permitting A2L refrigerants using the same shaft exception currently available to only A1 refrigerants and why that is consistent other codes and standards regulating the application, including what will be the provisions of the 2027 IMC.
Approving Modification of Refrigerant Piping Shaft Requirements of the 2021 and 2024 International Mechanical Code (IMC) by Permitting an Exception for All Refrigerant Groups
Code officials regulating multifamily buildings using state and local mechanical codes based on the 2021 and 2024 International Mechanical Code© (IMC) should grant a modification to eliminate the IMC Section 1109.2.5 requirement to provide a shaft for refrigerant piping containing quantities of other than Group A1 refrigerants below the tabular safety limits in IMC Table 1103.1.
Section 105.1 of the 2021 IMC and Section 104.2.4.1address permissible modifications of the code for individual cases provided the strict letter of the code is impractical and that “the modification is in compliance with the intent and purpose of this code and does not lessen health, life and fire safety requirements.”
Until the 2021 edition of the IMC, refrigerant piping that penetrated two or more floor ceiling assemblies was not required to be enclosed in a fire-resistance rated shaft provided the refrigerant quantity it contained did not exceed the limits of Table 1103.1 for the smallest occupied space through which the piping passed. IMC Table 1103.1 is duplicated from ASHRAE Standard 34, Designation and Safety Classification of Refrigerants© Table 4-1, Refrigerant Data and Safety Classifications.
This is technically founded; a core purpose of Table 4-1 of ASHRAE 34 and IMC Table 1103.1 is to establish the allowable quantity of refrigerant that can be released into an occupied space without creating a fire or human health hazard.
The 2021 and 2024 IMC limit the exception to the shaft requirement to piping containing Group A1 refrigerants which is inconsistent with ASHRAE 15, Safety Standard for Refrigeration Systems©. The parallel requirement in ASHRAE 15-2022, Section 8.10.3, Exception 4, permits the shaft exception for all refrigerants. Similarly, the 2024 Uniform Mechanical Code, Section 1109.3, Exception (4), permits the shaft exception for all refrigerants.
The IMC limitation to Group A1 refrigerants for the shaft exception was, according to the proponent of the code change that introduced it, (Julius Ballanco, P.E.), unintentional, and the result of the submission of an early draft of a code change proposal (M99-18) addressing more than sixty new sections, subsections, and tables addressing refrigerant piping. Mr. Ballanco has published a July 10, 2024, engineering analysis (full letter shown below this article) entitled, Refrigerant Piping Connecting (or Passing Through) Multiple Floor Levels, in which he states:
“SSPC 15 Refrigerant Piping Working Group had nine revisions to the original draft of the piping requirements. During those revisions, the limitation for shaft alternatives to only systems using Group A1 refrigerants was removed. There was no technical justification for limiting the shaft alternative to a single group of refrigerants. With the anticipated increased use of Group A2L refrigerants, it was noted that the shaft alternative must also apply to these refrigeration systems.”
Mr. Ballanco’s analysis also explains that only procedural deadlines within ASHRAE’s process for submitting code changes to other codes and standards prevented ASHRAE from proposing that Exception 2 of Section 1109.2.5 in the 2024 IMC be applicable to all refrigerant piping instead of only Group A1 refrigerants.
ASHRAE is a co-proponent of IMC code change M75-24 (see page 143 of 167), which returns the applicability of Exception 2 to all refrigerants. M75-24 was passed unanimously by the IMC hearing committee at the April 2024 committee action hearing (See page 222 of 314) and received no public comments in the subsequent public comment period. In accordance with the International Code Council’s code development process, M75-24 will be on the consent agenda for the 2027 IMC. This means that M75-24 will be codified, and the 2027 IMC will not limit the refrigerant pipe shaft exception to only Group A1 refrigerants.
Section 1109.2.5 in the 2021 and 2024 IMC is impractical because, due to US Environmental Protection Agency rules regulating the Global Warming Potential of refrigerants, no Group A1 refrigerant is available for use in residential applications. Residential applications instead must use Group A2L refrigerants which in turn require shafts if complying with the letter of the 2021 or 2024 IMC.
Providing shafts for Group A2L refrigerant piping requires significant modifications to typical multifamily housing design. Further, Section 1109.3.2 requires refrigerant pipe shafts containing Group A2L or Group B2L refrigerants to be provided with drainage and ventilation. Where mechanically ventilated, ventilation must be either continuous – a waste of operational energy - or initiated with refrigerant detection. Where refrigerant quantities comply with Table 4-1 of ASHRAE 34 and IMC Table 1103.1, such shafts limit usable floor space for no additional safety benefit and at substantial additional cost.
The purpose of the IMC, as given in Section 101.3, is “to establish minimum requirements to provide a reasonable level of safety, health, property protection and general welfare by regulating and controlling the design, construction, installation, quality of materials, location, operation and maintenance or use of mechanical equipment or systems.”
Permitting a modification of Exception 2 to Section 1109.2.5 of the 2021 and 2024 IMC, that would expand the applicability of the exception to more refrigerant groups than Group A1, is consistent with establishing a minimum requirement that provides a reasonable level of safety.
Code officials are encouraged to permit multifamily buildings that comply with the refrigerant pipe shaft requirements of ASHRAE 15-2022, and the 2027 IMC as detailed in code change M75-24.
JULIUS A. BALLANCO, P.E.
JB ENGINEERING AND CODE CONSULTING, P.C.
President
July 10, 2024
Refrigerant Piping Connecting (or Passing Through) Multiple Floor Levels Based on ASHRAE 15 with a Reference to the ICC International Mechanical Code
Executive Summary: Where refrigerant piping passes through different floor levels in a building, design professionals have the option of locating the piping in a fire-resistance rated pipe shaft, or within the building elements with each floor/ceiling penetration properly protected.
The 2021 and 2024 editions of the ICC International Mechanical Code have a limitation on refrigeration systems using Group A1 refrigerants for exceptions to the pipe shaft requirements. This limitation was only proposed, but not accepted, by ASHRAE 15. The limitation is being removed in the 2027 edition of the Mechanical Code. Code Officials should accept the allowance of the exceptions for any system, in accordance with alternative approval.
Pipe Shaft Option: When refrigerant piping is located in a pipe shaft, the Building Code regulates the fire- resistant rating of the shaft. Shafts that connect three stories or less must be 1 hour fire-resistance rated. Shafts connecting four or more stories must be 2-hour fire-resistance rated. Every pipe penetration of the shaft wall, whether horizontal or vertical, must be protected with a through penetration pipe protection to maintain the fire-resistance rating of the shaft.
When the refrigerant piping contains a Group A2L refrigerant, the pipe shaft must be ventilated. The ventilation can either be by natural or mechanical means. If natural ventilation is selected, a 4-inch round duct or pipe must be at the base of the shaft and open to the outdoors. There must also be an opening at the top of the shaft, to allow the free flow of air for natural ventilation.
If the shaft is mechanically ventilated, a refrigerant detector is required at the base of the shaft to detect any leaking refrigerant, thus activating the mechanical ventilation. The ventilation rate is based on the inside area of the shaft. ASHRAE 15 specifies the ventilation rate for the given size of the shaft.
Penetration Protection Option: Piping is typically enclosed within the building elements. Refrigerant piping may also be enclosed within the building elements. Where the refrigerant piping passes through a floor/ceiling assembly, the annular space around the pipe must be protected with a through penetration protection means. This is typically accomplished with a fire rated caulking material.
If the refrigerant piping passes through a fire-resistance rated wall assembly, the annular space must be protected with a through penetration protection means. The through penetration protection must be the same or higher rating than the wall assembly.
Substantiation Detailing the Executive Summary
The refrigerant piping requirements in the 2022 edition of ASHRAE 15 have been completely rewritten. The new requirements were developed by the Refrigerant Piping Working Group of SSPC 15. Many of the piping requirements remain the same as previous editions of the standard, merely coordinated into a new format.
One of the issues that appears confusing is the installation of refrigerant piping between multiple floors, specifically three or more floors. Section 9.12.1.5 states, in part, “Refrigerant piping that penetrates two or more floor/ceiling assemblies shall be enclosed in a fire-resistance-rated shaft enclosure. The fire- resistance-rated shaft enclosure shall comply with the requirements of the building code.”
The following section, 9.12.1.5.1, lists alternatives to installing refrigerant piping in a fire-resistance rated shaft. The second item listed for shaft alternatives states, “Piping in a high-probability system where the refrigerant concentration does not exceed the amounts shown in ASHRAE Standard 34, Table 4-1 or 4-2, for the smallest occupied space through which the piping passes.”
While both Section 9.12.1.5 and 9.12.1.5.1 appear to be new requirements, they are actually a rewrite of Section 8.10.3 of the 2019 and prior editions of ASHRAE 15. Rather than including exceptions to the shaft requirements, the new Section 9.12.1.5.1 uses the term, “shaft alternative.” In effect, shaft alternatives are exceptions to the shaft requirements.
The requirement for a pipe shaft dates back to when the Building Code mandated pipe shafts where piping extended three or more stories in a building. The 1984 BOCA Building Code had the following statement in Section 1410.4:
Section 1410.4 Ducts and pipe shafts: In all buildings other than buildings of Use Group R-3, vertical pipes arranged in groups of two or more which penetrate two or more floors and occupy and area of more than 1 square foot …. shall be enclosed by construction having a fireresistance rating specified in Table 401.
It should be noted that Use Group R-3 is the classification for one- and two-family dwellings.
Section 9.12.2.2 of ASHRAE 15 specifies requirements to ventilate a pipe shaft where refrigerant piping using Group A2L refrigerants is used. Shaft ventilation can be accomplished by either natural or mechanical means. For natural ventilation, Item a of Section 9.12.2.2 requires a minimum of a 4-inch diameter pipe, duct, or conduit at the lowest point of the shaft and open to the outdoors. A means of make up air must be at the top of the shaft.
Mechanical ventilation, identified in Item b of Section 9.12.2.2, is based on the area of the pipe shaft. Table 9-12 specifies the minimum ventilation rate. A pipe shaft of 20 square inches or less requires a minimum of 100 cfm of ventilation. A pipe shaft greater than 20 square inches, and less than or equal to 250 square inches, requires a minimum of 200 cfm of ventilation.
A pipe shaft remains an option for enclosing refrigerant piping. The ICC International Building Code has the following requirement for a shaft fire-resistance rating:
713.4 Fire-resistance rating. Shaft enclosures shall have a fire-resistance rating of not less than 2 hours where connecting four stories or more, and not less than 1 hour where connecting less than four stories. The number of stories connected by the shaft enclosure shall include any basements but not any mezzanines. Shaft enclosures shall have a fire-resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours. Shaft enclosures shall meet the requirements of Section 703.2.1.1.
By 1987, all of the model building codes were revised to remove the mandatory requirement for a pipe shaft. A pipe shaft was still permitted as an optional design, however, the building codes added extensive pipe penetration requirements for floor/ceiling penetrations when a pipe shaft is not installed. Those requirements remain in the current ICC International Building Code. Section 714 specifies penetration protection requirements. When a through penetration firestop system is used to protect the annular space, the system must be tested to ASTM E814 or UL 1479.
There are special exceptions for penetrations of copper and steel pipe 6 inches in diameter or less. When passing through concrete or masonry, the annular space can be filled with mortar, provided the penetration does not allow the passage of smoke or flame.
Item b in Section 9.12.1.5.1 of ASHRAE 15 is consistent with the International Building Code allowance for multi-floor piping with penetration protection rather than a pipe shaft. ASHRAE 15 directs the user to the Building Code to determine the requirements for penetration protection.
When utilizing Item b in Section 9.12.1.5.1, the design professional must perform an analysis of the potential leak of refrigerant into the smallest space in which the piping passes. The 2022 edition of ASHRAE 15 added new requirements for analyzing potential refrigerant leaks. This included the addition of effective dispersal volume charge (EDVC), as well as, effective dispersal volume (EDV). Section 7.2.3.1.1 added exempted spaces when determining the EDV. The section reads, “The areas that contain only continuous refrigerant piping, or contain only joints and connections that have been tested in accordance with Section 9.13, are exempt from the effective dispersal volume calculation unless these areas are part of connected spaces per Section 7.2.3.2.”
Section 9.13, referenced in the exempted spaces section, is the new robust testing requirements for field installed refrigerant piping. Testing is required for all field installed refrigerant piping, hence, if the piping installation complies with ASHRAE 15, spaces containing only the piping, including joints and connections, are exempt from the EDV calculations.
Where the refrigerant piping, connecting three or more stories, is not located in a fire-resistance rated shaft, Item b of Section 9.12.1.5.1 requires an analysis of the leak potential into the spaces in which the piping passes through. However, Section 7.2.3.2 exempts spaces from the EDV calculation if the space only contains tested refrigerant piping, joints, and connections. When installed in such a manner, the International Building Code requires all pipe penetrations of floor/ceiling assemblies to be properly protected.
ICC International Mechanical Code: At the time the ASHRAE SSPC 15 Refrigerant Piping Working Group began rewriting the refrigerant piping requirements in ASHRAE 15, it was noted that the refrigerant piping requirements in the 2018 edition of the ICC International Mechanical Code were woefully inadequate. A code change was submitted, using an early draft of the changes to the refrigerant piping requirements in
ASHRAE 15. Included in that early draft were the refrigerant pipe shaft provisions listed as Section 1109.2.5. Rather than shaft alternatives, the code change listed exceptions to a refrigerant pipe shaft section.
The second exception in the proposed code change added a limitation as only being applicable to refrigeration systems using Group A1 refrigerants. The exception reads:
2. Piping in a direct system using Group A1 refrigerant where the refrigerant quantity does not exceed the limits of Table 1103.1 for the smallest occupied space through which the piping passes.
This limitation for systems using Group A1 refrigerants was part of a very large code change. Most of the emphasis and review were of the other sections in the proposed change. Exception 2 was not identified in the code change substantiation, nor was it discussed during testimony on the code change.
SSPC 15 Refrigerant Piping Working Group had nine revisions to the original draft of the piping requirements. During those revisions, the limitation for shaft alternatives to only systems using Group A1 refrigerants was removed. There was no technical justification for limiting the shaft alternative to a single group of refrigerants. With the anticipated increased use of Group A2L refrigerants, it was noted that the shaft alternative must also apply to these refrigeration systems.
When the exception to Section 1109.2.5 was added to the 2021 ICC International Mechanical Code, the code became inconsistent with ASHRAE 15. The 2019 edition of ASHRAE 15 did not include the update from the Refrigerant Piping Working Group, however, the standard always permitted the shaft exception for a system using any refrigerant.
The final approval of the refrigerant piping rewrite to ASHRAE 15 occurred in the early part of 2022, after the final consideration of code changes to the 2024 ICC International Mechanical Code. In accordance with ASHRAE policy, a code change could not be submitted to ICC to correct exception 2 to Section 1109.2.5 since the piping change had not been accepted by ASHRAE.
The 2022 edition of ASHRAE 15, which is referenced in the 2024 edition of the ICC International Mechanical Code, updated the refrigerant piping requirements. The shaft alternatives allowable for all refrigerants was included in the 2022 edition of ASHRAE 15. Thus, there is a conflict between the Mechanical Code and the referenced standards regarding the exception or alternative to refrigerant pipe shafts.
The SSPC 15 Code Change Working Group noted this conflict and proposed a change, M75-24, to the 2027 edition of the ICC International Mechanical Code to remove the limitation applying to only Group A1 refrigerants. Code change M75-24, sponsored by ASHRAE and others, was unanimously approved by the Mechanical Code Committee. The result of this code change will make the Mechanical Code consistent with ASHRAE 15 regarding the allowance of the exception, or shaft alternative, being applicable to all refrigeration systems.
It is appropriate for code officials to grant an alternative approval in accordance with Section 104.2.3 of the ICC International Mechanical Code. The alternative approval would be to allow the use of Exception 2 to Section 1109.2.5 as applying to a refrigeration system using any refrigerant. The alternative approval would be consistent with ASHRAE 15 and the 2027 edition of the ICC International Mechanical Code.
Summary: ASHRAE 15 grants the design professional the option to install refrigerant piping in a fire- resistance rated shaft, or to protect every floor/ceiling penetration in accordance with the Building Code. Code Officials enforcing the 2021 or 2024 edition of the ICC International Mechanical Code should grant an alternative approval for refrigeration systems using refrigerants, other than Group A1 refrigerants, to not be located in a pipe shaft based on the requirements in ASHRAE 15.
Respectfully submitted,
Julius Ballanco