Overview
ISO 9972:2015 - Thermal performance of buildings - Determination of air permeability of buildings - Fan pressurization method - specifies field measurement of a building’s air permeability using mechanical pressurization or depressurization. The standard defines how to measure air flow rates across the building envelope at a range of indoor‑outdoor static pressure differences and how to express results such as air leakage rate, air change rate, effective leakage area and specific leakage rates. ISO 9972:2015 is intended primarily for single‑zone buildings or multi‑zone buildings treated as single‑zone by opening internal connections or equalizing pressures.
Key topics and requirements
- Test method: Use of fan‑based mechanical pressurization/depressurization (fan pressurization method) to induce controlled pressure differences and measure resulting air flow.
- Scope limits: Intended for whole‑building or part‑building envelope measurements; does not address air permeability of individual components.
- Measurement outputs: Air leakage rate, air change rate (per internal volume), air permeability (per envelope area), effective leakage area and specific leakage rates referenced to a defined pressure difference.
- Test conditions and preparation: Guidance on measurement conditions (temperature and wind considerations), building preparation (opening/closing interior openings), and isolation of HVAC or other systems during the test.
- Instrumentation: Requirements for air‑moving equipment, pressure‑measuring devices, airflow measurement systems and temperature measurement (general instrument categories are specified).
- Procedure & reporting: Steps covering preliminary checks, pressure sequences, zero‑flow correction, calculation methods and test report content.
- Uncertainty: Discussion and recommended procedures for estimating measurement uncertainty and reference values (internal volume, envelope area, net floor area).
Practical applications and users
ISO 9972:2015 is used for:
- Verifying building airtightness and compliance with design or regulatory requirements
- Comparing air permeability across buildings or building types
- Assessing effectiveness of retrofit measures by measuring leakage reduction before/after works
- Supplying input data for energy models to estimate infiltration heat loads (note: the method does not directly measure natural infiltration - tracer gas methods are needed for direct infiltration rates)
Typical users:
- Building energy assessors and auditors
- Test technicians and contractors performing airtightness testing
- Architects and HVAC engineers involved in energy performance design
- Retrofit specialists and building certifiers
Related standards
- ISO 7345 (referenced for thermal quantities and definitions)
- ISO 9972:2015 replaces ISO 9972:2006
- Tracer gas methods are noted as alternative approaches when direct measurement of infiltration rate is required
Keywords: ISO 9972:2015, air permeability, fan pressurization method, air leakage, building envelope, airtightness testing, air change rate, effective leakage area.