Building Codes

ACCA helps contractors comply with building codes. And we help code officials understand HVAC.

The purpose of building codes are to guide government agencies in meeting their minimum obligations to protect the general welfare of the population they serve. Codes are designed to prevent damage to property, as well as injury or death to persons, and these objectives are accomplished by applying accumulated knowledge to the avoidance, reduction, or elimination of definable hazards.

Codes generally apply to the built environment and, when adopted by the pertinent authority, become lawful requirements that mandate compliance. An authority may write its own code document or may adopt other code documents. Different states and/or municipalities are free to adopt different codes.

Standards are usually regarded only as recommendations that do not have the force of law, unless the standard is adopted by the authority having jurisdiction. It is common for sections of a local code to refer to nationally recognized standards. In many instances, entire sections of the standards are adopted into the code by reference, and then become legally enforceable.

There are three main organizations in the United States who write codes that impact the indoor environment industry: IAPMOICC and NFPA.

Current Activities

Update on New Code Change Cycles

The International Code Council (ICC) and the International Association of Plumbing and Mechanical Officials (IAPMO) are currently mid-way through their respective code change cycles. The ICC’s “Group A” codes have concluded their code change process, which include their mechanical, plumbing, fuel gas and residential codes. The ICC energy code change cycle has commenced and proposals were submitted by October 2021. In addition, both the IAPMO Uniform Mechanical Code (UMC) and Uniform Plumbing Code (UPC) have completed their proposal phase and are now into the public comment period. The above code change cycles will result in the publication of the 2024 editions.

The above activity falls under the scope of the ACCA Codes Subcommittee, which takes a proactive role in developing proposed code changes based on member input, plus reviewing other code proposals published for public comment to provide contractor guidance. The Codes Subcommittee is always seeking CONTRACTOR input on changes needed for the above codes. If there are any areas of the codes that you feel need improvement, or “fixing,” please send your ideas or suggestions to ACCA staff at Your suggestions do not have to be in formal code language, just let us know where (and why) the problem or improvement is needed.

Shown below is an update on current code change activities.

International Mechanical Code (IMC)

During public comment hearings held in September 2021, the ICC membership considered code change proposals in light of comments received. Shown below are some highlights.

  • Despite ACCA testimony in favor of its modified proposal to add permanent attic stairs for servicing HVAC equipment in new construction, the code officials in attendance voted to reject. The National Association of Home Builders (NAHB) once again voiced opposition. ACCA’s Codes Subcommittee had developed the proposal based on an amendment to the Georgia building code that was effective January 2020.
  • Based on comments and testimony from ACCA and other parties, a proposal to require new HVAC systems to be designed to accommodate MERV 13 filters will be located as a new non-mandatory appendix.
  • Another proposal to require return air ducts for bathrooms as an option was rejected based on opposition from ACCA and others. ACCA supported this rejection as moist bathroom air should be exhausted and not returned.
  • All proposed changes to the mechanical codes covering the use of A2L refrigerants in residential applications were approved. They will be published in the 2024 editions. ACCA joined others in supporting these changes, which were based on applicable UL and ASHRAE standards
International Energy Conservation Code (IECC)
For the upcoming ICC energy code change cycle, ACCA has submitted two proposals, as described below.

  • For Chapter 11, Energy Efficiency, in the 2021 International Residential Code (IRC), a proposed exception to leak testing ducts located inside conditioned space if a duct airflow balancing procedure is conducted, as outlined in ACCA 5 QI, HVAC Quality Installation Specification.
  • Also for Chapter 11 in the IRC, the proposed addition of ACCA Manual D, Residential Duct Systems. Currently, ACCA Manual J (load calculations) and Manual S (equipment sizing) are already required by Chapter 11. All three ACCA standards are required for ensuring an energy-efficient HVAC system is designed and installed per the energy codes.
New IECC Code Development Process

Earlier this year, the ICC Board shifted its energy code development process to a consensus standards committee, based on ANSI procedures. Two new committees were formed, one for commercial and the other for residential. Additionally, working groups have been formed which will review proposed energy code changes and make recommendations to their respective committees. ACCA has applied for membership on the HVAC/Water Heating Working Group of the Residential Energy Code Committee. It is hoped that this new committee process, including its working groups, will provide a better environment for development of logical code requirements. Meetings to review submitted energy code proposals will be held during 2022.

IAPMO Uniform Mechanical Code (UMC)

During “virtual” meetings held earlier this year, the UMC Technical Committee considered code change proposals. Promising news from the above meeting includes the approval of proposed revisions to add comprehensive coverage for A2L “mildly flammable” refrigerants for use in home comfort systems. Last year, a special A2L Task Force met many times to develop consensus-based proposals for the coverage. ACCA participated in these meetings to ensure that the interests of our membership were represented to keep contractors and their customers safe. ACCA has voting membership on the UMC TC.

Proposals to Eliminate Press-Connect Fittings for Refrigerant Piping

During the above meeting of the UMC TC, proposals were narrowly approved which would eliminate press-connect fittings for refrigerant piping, including piping for A2L refrigerants. The proposals would only allow brazed fittings to be used. Currently, the UMC allows for press-connect fittings for refrigeration if they are tested and certified to UL Standard 207. ACCA and the HVACR industry continue to oppose these changes. Listed press-connect fittings have a proven safety record in the field as installed per manufacturer’s instructions. In addition, there needs to be a viable option if there are situations where brazing is not allowed per local codes.

The TC’s actions on the above proposals are now out for public comment with a due date of January 4, 2022. The TC will meet again in May 2022 to consider public comments and finalize their recommendations.

The UMC is developed by IAPMO using the American National Standards Institute's (ANSI) consensus development procedures. The code is adopted as the California Mechanical Code, and by other states such as Nevada and New Mexico.

Update on 2020 National Electrical Code Requirement for GFCI Protection on Outdoor HVAC Equipment

The Standards Council of the National Fire Protection Association (NFPA) has approved a Tentative Interim Amendment (TIA) which delays the effective date for 210.8(F) in the 2020 National Electrical Code (NEC) until January 1, 2023. The above requirement mandates GFCI protection for outdoor equipment, including HVAC. The delay only applies to variable speed HVAC equipment.

The above TIA was submitted by the Minnesota Department of Labor and Industry, and narrowly focused on variable speed HVAC equipment, instead of all HVAC equipment as with other submitted TIA proposals that have failed NFPA's balloting process over the past year.
In addition, the Council authorized the formation of a task group comprised of GFCI and HVAC manufacturers, as well as other interested parties, “to evaluate and reach an informed technically substantiated resolution to the issues raised.” In response, ACCA Codes Subcommittee Chairman Manny Chaves has appointed Ed Lehr, President, Jack Lehr Heating, Cooling & Electric, Allentown, PA, to represent ACCA on this task group.

Numerous proposals and appeals have been submitted to NFPA to delay the effective date due to the high incidence of nuisance trips in the field. The nuisance trips are due to the electrical incompatibility between currently available GFCI devices and HVAC equipment. Although the above TIA applies only to variable speed compressors, there is evidence of nuisance trips on single speed equipment. This aspect will have to be resolved as well. ACCA has gone on record as supporting all proposed TIAs calling for the delay until a resolution can be found.

The ACCA Codes Subcommittee continues to encourage ACCA members to request their jurisdictions to delete the above requirement if and when they consider adopting the 2020 NEC as their state or local code. The template can be found at the link shown below.

An update on which states have adopted (or are adopting) the 2020 NEC as of October 1, 2021 can be found at the link shown below.
Learn where the National Electrical Code® (NEC®) is enforced. | NFPA

Currently, 14 states have adopted the 2020 NEC as modified by deleting or delaying the above requirement, with 3 more states processing similar amendments. For more information please contact ACCA’s Manager of Codes and Standards at

Information for Contractors

ACCA Template to Request Jurisdictions Not to Adopt GFCI Protection for Outdoor HVAC Equipment in 2020 NEC – Nuisance Trip Issue

The 2020 Edition of NFPA 70, the National Electrical Code (NEC) now requires ground fault circuit interrupter (GFCI) protection for outdoor outlets, which would include disconnects for HVAC/R condenser units and other outlets. Read more here.

ACCA Releases Template to Request Jurisdictions To Exempt Leak Testing of Ducts Within Thermal Envelope – New Energy Code Requirement 

The ACCA Codes Subcommittee developed a Template for members to request an exemption from this testing requirement.   Different states adopt codes at different times, Missouri recently adopted the IRC even though it is not published.  A useful tool to determine which code is adopted and enforced in your state can be found on ICC’s website. Read more here. 

Adoption of ICC Codes in the U.S.

The International Code Council’s (ICC) website details “State Adoptions” and “Local Adoptions” of the varied ICC codes (e.g., IBC, IECC, IMC, IPC, IRC, etc.) across the U.S. ICC’s “State Adoption” link provides information as to when the codes where adopted as well as to the key code contacts within a State. ICC’s “Local Adoption” link details county-by-county breakdowns of which version of the varied ICC codes are utilized in a given county by State. Learn more here.

A number of substantive changes have been made during ICC’s last code change cycle, which culminated in the publication of the 2021 editions. Below is a summary of those changes.  More summaries will be added as ICC publishes their new editions.

Summary of Significant Changes in the 2021 Edition of the International Mechanical Code

Reciprocal ICC Membership for ACCA Members

Through a special agreement between ACCA and the International Code Council (ICC), ACCA Members may apply for a free membership to the Code Council. No other building code association offers you more I-Code resources to help enhance your code knowledge. Take Advantage of These Code Council Benefits:
  • Discounts on ICC certification renewals
  • Best pricing on I-Code resources and online training
  • Free access to ICC’s online Career Center
  • Discounts up to 25% off code publications
  • Opportunities to participate in member councils, committees and more
To receive these benefits, download, complete and submit this simple application.

Codes 101 Brochure

This brochure covers the basics of codes and standards and is aimed at providing contractors with a general understanding of these issues so that they can become more involved in the code development processes that affect the HVAC industry. Download it.

Residential System Design Review Form

ACCA has crafted an easy-to-use evaluation of HVAC system design elements in the pertinent building codes. Download it.

Computing Infiltration Loads based on a Target Envelope Leakage Requirement

This Technical Note shows how to convert a maximum code allowable leakage limit (say, 3 or 5 ACH 50 per the ICC International Energy Conservation Code) to a Manual J infiltration CFM value, and then to the infiltration load contributions (Btuh) for sensible heating, sensible cooling, and latent cooling. It also discusses the use of blower door data for one or more test points. Download it.

ACCA Codes Committee (committee members only)

Get involved in ACCA’s Codes Committee and make a difference in the development and adoption of good building codes. For more info about becoming involved in the Codes Committee and ACCA's building code efforts, contact

Information for Code Officials

Residential System Design Review Form for Code Offices

ACCA provides a “review form” (that may be customized by code officials for the relevant ICC and IAPMO codes) that can serve as the cover page to a contractor’s permit submission.  Blank forms as well as completed examples and instructions to contractors can be found here.  

Brochures for Code Officials

ACCA has developed several brochures which help code officials verify residential load calculations, duct design and equipment selection in accordance with Manuals J, D, and S. While it’s not practical for code officials to verify every single aspect of these submissions, these brochures offer checklists for a simplified verification process. Download them.

Load Calculation Software

An important warning notice for code officials about the dangers of inappropriate load calculation software. Download it.

ICC PMG Membership Council

Visit the International Code Council's (ICC) Plumbing Mechanical Gas (PMG) Membership Council webpage for other resources like CodeNotes, High School Technical Training Program Toolkit, and technical partners information.

Bob's House

Bob's House - A case study for understanding the residential HVAC design process as described in the ACCA residential technical manuals. The book begins with the building plans and follows the process through the completion of the system design. Also included are useful appendices that explore what would happen to Bob's house if he were in a different city, or if his builder had used different building materials , as well as the impact of other possible scenarios and other possible variations. Other appendices discuss different equipment types, duct challenges, and an illustrative example of how information might be presented for a permit application. Click here to learn more

Video Training for Code Officials

ACCA has developed a three-part video series that aims to help code officials better understand the three main aspects of a proper residential HVAC system design: a load calculation, selecting the appropriate equipment, and proper duct sizing.  The basis for the videos are the code-referenced ACCA Manual J, Manual S, and Manual D.  The videos do not comprise a design course, but instead provide an overview of the design process and presents ACCA-recommended verification points.  This will better enable code officials to verify that a system was designed correctly.


Looking for CEUs?  

ACCA is now an ICC Preferred Education Provider. Earn .2 CEUs by passing a 30 question online exam and earn your course certificate.
Click here to learn more and sign up.

ACCA in Building Codes

For years, ACCA's technical manuals and standards have been an integral part of the national model building codes' requirements for proper HVAC design.  The following model codes currently reference, or have in the past referenced, ACCA's various design manuals and standards:

  • IAPMO's Uniform Mechanical Code
  • IAPMO's Uniform Swimming Pool, Spa, and Hot Tub Code
  • ICC's International Residential Code
  • ICC's International Energy Conservation Code
  • ICC's International Mechanical Code

To see the detailed references in each model code, including section excerpts, please see the document for the specific cycle:

ACCA Codes Development Position Statement

The model building codes are intended to ensure that our buildings are safe, sustainable, affordable, and resilient; they contain the minimum safeguards for their construction. Though the distinct code-promulgating organizations have different procedures for the development of their various codes, they all include provisions for the call for, publication of, discussion about, and voting on public code change proposals. These code change proposals are (ideally) intended to refine the codes by addressing gaps or moving them forward in their stated mission. 

In practice, however, the various players in the code development arena (code officials, design professionals, code consultants, trade associations, builders/contractors, manufacturers/suppliers, and government agencies) may submit code change proposals that are intended to give a specific process, product, or organization special consideration in the administration of a code. 

As a national trade association that represents more than 60,000 professionals and 4,000 businesses in the indoor environment and energy services community, ACCA does not support changes to the model codes that would limit a designer's options to provide quality service to their customer. ACCA recognizes that any aspect of a building system may be installed incorrectly due to subpar field practices. However, these installation issues should be addressed through the development of consensus standards on the specific issue, and not by code banning a viable design alternative.