Overview
ISO 9869-2:2018 - "Thermal insulation - Building elements - In‑situ measurement of thermal resistance and thermal transmittance - Part 2: Infrared method for frame structure dwelling" specifies an infrared (IR) thermography method for in‑situ measurement of thermal resistance and thermal transmittance (U‑value) of opaque building elements on existing buildings. The method is intended as a screening and diagnostic technique for frame‑structure dwellings with light thermal mass (daily heat capacity per ISO 13786 typically below 30 kJ/(m2·K)) and for surfaces that are high‑emissivity diffuse.
Key topics and requirements
- Measurement principle: Derive heat flux from the indoor surface temperature distribution (from an IR camera), the local total heat transfer coefficient, and an environmental temperature; calculate U‑value from heat flux and temperature difference.
- Apparatus required: infrared camera (thermography), heat transfer coefficient sensor, environmental temperature (ET) sensor, thermocouples and data logger - with specified performance and calibration needs.
- Surface conditions: applies to high‑emissivity, diffuse indoor surfaces and is designed to minimize solar/radiant interference (indoor measurements preferred).
- Measurement procedure: guidance on building and area selection, sensor placement, measurement conditions, measurement time, intervals and observation period suitable for light thermal mass components.
- Data handling: calculation methods for heat flow rate, heat transfer area and thermal transmittance; statistical approaches and evaluation of steady‑state assumptions for short observation periods.
- Quality and reporting: requirements on measurement accuracy, uncertainty analysis (informative annexes), and contents of test reports.
Practical applications
- Thermal diagnostics and retrofit screening: rapid identification and quantitative evaluation of defect areas (gaps, insulation defects, thermal bridges) in framed dwellings.
- U‑value verification: in‑situ verification of thermal transmittance for existing partitions, walls and ceilings with light thermal mass where heat flow meter installation is impractical.
- Energy audits and building inspections: non‑invasive thermographic surveys combined with localized sensors to produce actionable U‑value estimates.
- Research and quality control: comparative studies of insulation performance and post‑installation verification for renovation projects.
Who should use this standard
- Building energy assessors, thermographers and retrofit contractors
- Building inspectors and certification bodies
- Researchers and laboratories performing field measurements
- HVAC and façade specialists involved in energy retrofit verification
Related standards
Keywords: ISO 9869-2:2018, infrared method, in-situ measurement, thermal transmittance, U-value, thermography, heat transfer coefficient sensor, ET sensor, frame structure dwelling, building diagnostics.