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CAN CGSB 149.12-2017: Infrared Thermography Method for Determining Building Envelope Heat Loss Coefficient
A comprehensive guide to scope, technical specifications, and compliance for building energy performance assessment using infrared thermography
1. Scope and Application
CAN CGSB 149.12-2017, titled Determination of the Overall Envelope Heat Loss Coefficient of Buildings by the Infrared Thermography Method, establishes a standardized methodology for quantifying the thermal performance of building envelopes. This standard is applicable to both residential and commercial buildings, whether existing or newly constructed, and is widely used in energy audits, commissioning, and retrofit evaluations.
The primary purpose of the standard is to provide a reliable, non-destructive technique for measuring the overall envelope heat loss coefficient (often expressed as U-value or heat loss per degree temperature difference) using infrared (IR) thermography. It enables practitioners to assess thermal continuity, detect insulation defects, and verify compliance with thermal performance criteria.
The standard covers both qualitative and quantitative thermographic surveys. Qualitative surveys identify thermal anomalies (e.g., air leakage, missing insulation), while quantitative surveys calculate the actual heat loss coefficient under controlled environmental conditions. The scope includes interior and exterior scanning procedures, equipment requirements, and data analysis guidelines.
Tip: For best results, combine a CAN CGSB 149.12 survey with a blower door test (CAN CGSB 149.10) to isolate air leakage from conductive heat losses.
2. Technical Requirements
2.1 Equipment Specifications
Infrared cameras used under this standard must meet minimum performance criteria:
| Parameter | Requirement |
|---|---|
| Thermal sensitivity (NETD) | ≤ 0.05 °C at 30 °C |
| Accuracy | ± 2 °C or ± 2% of reading |
| Spectral range | 7.5 – 14 μm |
| Minimum image resolution | 320 × 240 pixels |
| Calibration interval | Not exceeding 12 months |
Additionally, the camera must have adjustable emissivity settings (±0.01) and be calibrated with a certificate traceable to a national standard.
2.2 Environmental Conditions
The standard specifies strict site conditions to ensure valid quantitative measurements. Table 2 summarizes the required environmental parameters during a survey.
| Parameter | Condition |
|---|---|
| Indoor-to-outdoor temperature difference | ≥ 10 °C (preferably 15 °C) |
| Wind speed at building height | ≤ 5 m/s |
| Solar radiation (direct) | Avoid direct sunlight on surfaces for 24 h prior |
| Precipitation | No rain, snow, or fog during survey |
| Stabilization period after weather change | At least 4 hours |
Surveys should be conducted when the building’s HVAC system is operating in normal heating or cooling mode. For quantitative heat loss coefficient calculations, the indoor temperature must be monitored and recorded at multiple points, and the outdoor temperature averaged over the test period.
2.3 Survey Procedures
The standard distinguishes between interior and exterior thermographic surveys. Interior surveys are preferred for conductive heat loss analysis because they avoid reflections from the sky and surroundings. Exterior surveys are used for detecting air leakage and moisture but require stringent emissivity corrections.
Thermographic images must be taken with the camera normal to the surface (angle ≤ 60° from perpendicular). Reflected apparent temperature must be measured using a reflector method, and emissivity values must be determined for each material type (e.g., painted drywall ε ≈ 0.90–0.95).
Warning: Surveying shiny metallic surfaces (low emissivity) without proper correction can lead to significant errors. Use masking tape or flat paint to increase emissivity if needed.
3. Implementation Highlights
Practitioners following CAN CGSB 149.12-2017 should emphasize proper training and equipment handling. The standard recommends that thermographers hold a Level 1 or higher certification from a recognized infrared training program (e.g., ITC, ASNT).
Key steps in a quantitative survey include:
- Pre-survey building inspection and weather forecasting.
- Setup of temperature loggers and weather station.
- Measuring surface temperatures from multiple equidistant spots.
- Calculating heat loss coefficient using the thermal resistance network method or direct heat flux measurements.
- Correcting for radiation and convection coefficients based on surface orientation and wind speed.
The standard provides calculation formulas for the overall envelope heat loss coefficient, accounting for both convective and radiative components. A complete report must include all raw thermal images, environmental data, equipment calibration certificates, and the calculated U-value with uncertainty analysis.
Success: When properly applied, CAN CGSB 149.12 can detect insulation voids, thermal bridging, and air leakage with accuracy comparable to guarded hot-box methods, but at a fraction of the cost and time.
4. Compliance Notes and Certification
Compliance with CAN CGSB 149.12-2017 is increasingly required for building energy codes, green building certifications (e.g., LEED, Passive House), and federal incentive programs such as NRCAN’s Greener Homes Grant. The standard forms part of the National Building Code of Canada’s referenced documents for thermal performance verification.
To achieve compliance, the following are mandatory:
- Use of a calibrated IR camera meeting the standard’s specifications.
- Conducting surveys under the prescribed environmental window.
- Employing a qualified thermographer with documented training.
- Maintaining a thorough audit trail of images and calculations.
Regular equipment recalibration (annually or per manufacturer’s recommendation) is essential. Laboratories offering calibration services must be accredited to ISO/IEC 17025.
Important: Non-compliance with environmental conditions can invalidate quantitative results. If conditions are marginal, the standard requires that the uncertainty range be reported, and the survey classification downgraded to qualitative-only.
5. Frequently Asked Questions
Q: What is the difference between qualitative and quantitative thermography under this standard?
A: Qualitative thermography identifies relative temperature differences to find anomalies (e.g., thermal bridging). Quantitative thermography calculates the actual heat loss coefficient (U-value) using measured surface temperatures and environmental data, requiring stricter conditions and equipment calibration.
A: Qualitative thermography identifies relative temperature differences to find anomalies (e.g., thermal bridging). Quantitative thermography calculates the actual heat loss coefficient (U-value) using measured surface temperatures and environmental data, requiring stricter conditions and equipment calibration.
Q: How often should the infrared camera be calibrated?
A: The standard requires calibration at intervals not exceeding 12 months. However, more frequent calibration is recommended if the camera is serviced, dropped, or used in harsh environments.
A: The standard requires calibration at intervals not exceeding 12 months. However, more frequent calibration is recommended if the camera is serviced, dropped, or used in harsh environments.
Q: Can CAN CGSB 149.12 be used for LEED v4 energy performance credits?
A: Yes. The standard is accepted as a supplementary test method for verifying building envelope thermal performance under LEED’s Minimum Energy Performance prerequisite and Optimize Energy Performance credit, provided the survey is executed by a qualified thermographer.
A: Yes. The standard is accepted as a supplementary test method for verifying building envelope thermal performance under LEED’s Minimum Energy Performance prerequisite and Optimize Energy Performance credit, provided the survey is executed by a qualified thermographer.
Q: What is the minimum temperature difference required for a quantitative survey?
A: The standard requires at least 10 °C difference between indoor and outdoor temperatures, with a preference for 15 °C to reduce measurement uncertainty.
A: The standard requires at least 10 °C difference between indoor and outdoor temperatures, with a preference for 15 °C to reduce measurement uncertainty.
Implementation guidance: 2026 — Review of CAN CGSB 149.12-2017 applies to studies conducted in that year.