ISO 5222-1:2025

Overview

ISO 5222-1:2025 defines standardized testing and calculation methods for the sensible heating recovery seasonal performance factor of heat recovery ventilators (HRVs). Intended for marking and comparison purposes, this second edition establishes the test conditions, procedures and calculation steps needed to determine how effectively an HRV recovers sensible heat over a heating season. The standard applies to HRVs covered by ISO 16494-1 and aligns terminology and stage naming with other parts of the ISO 5222 series.

Key topics and technical requirements

• Scope and purpose: Procedures for measuring and calculating the seasonal sensible heating recovery performance (F_sh) of HRVs.
• Test conditions: Standardized test points (T5, T6, T7) with specified outdoor/indoor dry-bulb temperatures (e.g., T5 = 2 °C outdoor / 21 °C indoor; T6 = 5 °C / 20 °C; T7 = 7 °C / 20 °C) used to represent application climates and to compute seasonal metrics.
• Performance metrics:
  • Gross sensible heating effectiveness (ε_sh) - measured effectiveness not corrected for leakage or motor heat gain.
  • Seasonal sensible heating recovery capacity (E_sh) and seasonal performance factor (F_sh) - calculated from bin-hour outdoor temperature distributions, capacity curves, and power input characteristics.
• Bypass and control functions: Methods to determine bypass outdoor temperature (T_b) and to account for bypass ventilation or fan speed control that reduces fan power when heat recovery is not energy-beneficial.
• Power measurements: Procedures for measuring fan power with and without bypass, power input to supplementary preheaters, and the power value of moving air.
• Frosting and low-temperature tests: Determination of frosting temperature and related test reduction points.
• Reporting: Required test report contents and informative annexes (schematics, default bin distributions, calculation examples, and report templates).

Practical applications and users

ISO 5222-1:2025 is useful for:

• Manufacturers verifying and declaring HRV seasonal sensible heating performance for product labels and datasheets.
• Independent test laboratories performing standardized HRV testing and certification.
• HVAC engineers and specifiers comparing HRV options for energy-efficient ventilation system design across climate zones.
• Regulators and certification bodies evaluating compliance with energy-performance labeling schemes or procurement specifications.
• Energy modelers incorporating validated HRV seasonal performance factors into building energy simulations.

By standardizing test methods, ISO 5222-1 helps ensure consistent, comparable HRV performance data, supports energy-efficient product selection, and enables fair comparison across manufacturers and climates.

Related standards

• ISO 16494-1 - normative reference for method of test and metric development for HRVs/ERVs.
• Other parts of the ISO 5222 series (ISO 5222-2, ISO 5222-3) for related performance factors and aligned terminology.