Overview
ISO 19916-3:2021 specifies laboratory test methods for evaluating vacuum insulating glass (VIG) with a rigid edge seal when subjected to temperature differences between the glass sheets. The standard defines specimen selection, apparatus, measurement procedures and reporting requirements to ensure reproducible assessment of thermal performance and stress behaviour under controlled temperature differentials. This part applies only to VIG with rigid edge seals (not flexible edge seals).
Key topics and technical requirements
- Scope and applicability
- Applies to vacuum insulating glass (VIG) samples with rigid edge seal only.
- Not applicable to VIG with flexible edge seals.
- Specimens
- Three specimens required.
- Size limits: 300 mm ≤ width/height ≤ 850 mm.
- Maintain at least 100 mm clearance between specimen edge and chamber wall.
- Selection rules: test the design with the lowest U-value or with minimum total nominal thickness within a product range.
- Apparatus
- Temperature chamber (single or two-room arrangement), specimen frame with insulating board, heat transfer control board (flat metal plate), thermocouples, data recorder and suitable adhesive tape.
- Instrumentation and thermocouples
- Thermocouple wire diameter ≤ 0.25 mm; thermal contact length ≥ 20 mm.
- Place thermocouples on hot/cold centre glass surfaces and on air (or control board) at 100–200 mm from the glass surface.
- Position tips midway between pillars and between adjacent pillar rows.
- Test procedure
- Specimen mounted vertically with all four edges free to bend (edge contact at corners ≤ 30 mm); seal gap to prevent airflow.
- U-value and thermal resistance measured per ISO 19916-1 prior to temperature-difference testing.
- Maintain a steady-state temperature profile: the glass surface temperature difference ΔT must meet a minimum derived from specimen thermal resistance (R_VIG) and reference conditions (air-to-air ΔT = 40 °C with reference heat transfer coefficients 8 and 23 W/(m2·K)).
- Control ΔT within ±5% of the average steady-state value for at least 1 hour.
- Calculate surface heat transfer coefficients from measured temperatures; adjust control board or HVAC if coefficients fall outside acceptable ranges.
- Reporting
- Test report content and failure-evaluation references are defined; failure criteria are evaluated from measured temperatures per the standard.
Applications and users
- Manufacturers of vacuum insulating glass validating product performance
- Independent test laboratories performing VIG certification and R&D
- Façade engineers, window system designers and architects assessing thermal stress and durability under temperature gradients
- Certification bodies and building code authorities requiring standardized thermal/stress test evidence
Related standards
- ISO 19916-1 - Basic specification and evaluation methods for VIG thermal and acoustic performance (referenced for U-value measurement)
- ISO 10292 - Reference internal/external heat transfer coefficients used in ΔT derivation
Keywords: ISO 19916-3, vacuum insulating glass, VIG, rigid edge seal, test methods, temperature differences, U-value, thermal resistance, thermocouples, heat transfer coefficient.