SMACNA Class C Leakage Standards: 2026 Statutory Context

In the 2026 Malaysian HVAC landscape, SMACNA Class C Leakage Standards are defined by the allowable leakage rate in relation to duct surface area and static pressure. While "Class C" is often associated with the DW/143 (UK) framework as a "High-Pressure" standard, in the SMACNA framework, it traditionally refers to a Seal Class C—which is the most basic level of sealing, generally limited to transverse joints only.

However, under the Energy Efficiency and Conservation Act (EECA) 2024 and MS 1525:2024, utilizing only "Class C" sealing is now largely non-compliant for commercial office environments in Malaysia, as these regulations now mandate Seal Class A (sealing all seams, joints, and penetrations) to meet energy intensity targets.

1. The Engineering Definition of Leakage Class

The SMACNA formula for predicting leakage is based on the Leakage Class ($C_L$), which correlates leakage to duct surface area and static pressure:

• $F$: Leakage rate ($cfm/100\text{ ft}^2$).

   

• $P$: Static pressure (inches w.g.).

• $C_L$: Leakage Class.

In the SMACNA hierarchy, the expected Leakage Class for a duct depends on its Seal Class and its shape:

2. Statutory Conflict: Seal Class C vs. EECA 2024

Under the current 2026 enforcement of EECA 2024, "Class C" sealing is essentially obsolete for new commercial installations.

• The "Energy Waste" Mandate: EECA 2024 legally defines air leakage as "Spent Energy." To satisfy the Building Energy Intensity (BEI) targets, the Suruhanjaya Tenaga (ST) now requires a minimum of Seal Class A for all ductwork operating above 500 Pa.

• MS 1525:2024 Compliance: The latest Malaysian Standard has moved toward the ASHRAE 90.1-2025 alignment, specifying that all duct systems must be sealed to Class A to ensure the Specific Fan Power (SFP) remains below 1.6 kW/m³/s.

• Leakage Class 4: For rectangular ducts, the industry "Gold Standard" is now Leakage Class 4 (which requires Seal Class A), as this is the only way to ensure the VFD-driven AHU operates at its optimized frequency without fighting "false load" from leaks.

3. DW/143 "Class C" vs. SMACNA

It is critical for contractors in KL to distinguish between the two standards, as many 2026 specifications now use them interchangeably in error.

• SMACNA Seal Class C: The lowest level of sealing (Transverse joints only).

   

• DW/143 Class C: A high-performance standard for high-pressure systems (up to 2000 Pa).

   

If your project specifies "Class C," verify whether they mean the SMACNA construction seal (which is likely non-compliant) or the DW/143 performance class (which is a high-spec requirement).

4. The "Fire Mode" Statutory Protocol

Leakage standards are a life-safety issue under BOMBA (JBPM) 2026 regulations.

• Smoke Leakage: In a "Smoke Spill" event, a duct with only Class C sealing will allow toxic smoke to "break out" into ceiling voids, potentially bypassing fire compartments.

• BOMBA Audit: For a building to receive its annual Fire Certificate (FC), the smoke extraction ducts must pass a Duct Air Leakage Test (DALT) ensuring they meet the high-integrity Seal Class A requirements.

5. Why Partner with EKG (Malaysia) SDN BHD?

• Technical Integrity: We refuse to install "Seal Class C" systems for commercial clients because they fail the 2026 REA (Registered Energy Auditor) inspections.

• Precision Testing: We perform DALT on all EKG (Malaysia) SDN BHD installations to verify a Leakage Class 4 or better, ensuring your facility is ready for ST and BOMBA witness testing.

• GITA Compliance: Our Seal Class A installations are the technical prerequisite for claiming your 100% Green Investment Tax Allowance (GITA).

Is your ductwork leaking energy or failing to meet the 2026 Seal Class A mandate?

Contact EKG (Malaysia) SDN BHD today for a specialized Duct Air Leakage Test (DALT) & Statutory Audit.