Thanks to thermography, there’s no longer a need to cut into walls and dig into a house’s innards to locate and identify the source of certain problems. Infrared cameras let you detect hidden defects – without breaking whatever is covering them!
These special cameras can detect:
- deficiencies in the airtightness or thermal insulation of the building envelope;
- water infiltration in a foundation or roof;
- condensation in a wall;
- a leak in certain heating systems;
- and more.
What is thermography?
Thermography is a technique for recording the temperature of objects and materials using infrared rays. Infrared cameras record the temperature at various points on the surfaces inspected. It displays these measurements in a colour image called a thermogram.
This image shows the recorded temperatures based on a colour code. Cold points are presented in a gradation of cold colours – green, blue and violet up to black, indicating the coldest temperature. At the other end, the higher an element’s surface temperature, the warmer its depiction, from yellow and orange on to red and then white.
Observation of the hottest or coldest surface points may reveal an anomaly. For example, a bluish portion of a wall on a thermogram taken from indoors in the winter may indicate missing thermal insulation. In this case, the same wall section examined by infrared camera from outdoors would appear in warm colours, showing heat loss.
How are the data interpreted?
Analyzing a thermogram is complex. Interpreting the data requires taking many factors into account. To understand what the colours are saying, factors to consider include the radiation characteristics of materials. For example, aluminium and brick do not absorb or radiate heat in the same way.
Also, when a technician is not using an infiltrometer to control for air pressure inside a building, the value of the information collected is heavily influenced by the prevailing atmospheric conditions at the time of the inspection. In this case:
- There must be a temperature spread of 10°C or more between indoors and outdoors to assess a building envelope. This makes wintertime ideal. Note that some older cameras require a bigger temperature spread because of their less advanced technical characteristics.
- Outdoor readings should be taken in good weather either very early in the morning or a few hours after sunset, because rain and sun alter the temperature of surfaces.
Who can do this type of analysis?
Not just anyone can be a thermographic inspector. It takes a combination of rigour and skill to get conclusive results. Images must be taken and interpreted by experts certified by the American Society for Nondestructive Testing (ASNT). Level 1 certification is required to use the camera and Level 2 to write the report.
After the inspection comes the report
Once the camera exploration and data analysis are completed, the inspector must provide a detailed report containing:
- digital infrared photos locating the problems detected;
- an explanation of the phenomena or construction details observed;
- diagrams showing the problem areas and the corrective measures required
- an explanation of the suggested corrective methods and what they involve.
The report should also contain a description of environmental conditions during the inspection and the image-taking parameters: temperature calibration, distance of the camera from the surfaces observed, emissivity of these surfaces, etc.
The identities and qualifications of the people handling the camera, interpreting the data and producing the conclusions from the analysis must be specified in the report.
How much does it cost?
The cost of a thermographic analysis is linked directly to the size of the job and the extent of the surfaces analyzed. Inspecting an entire house will cost more than looking at just one wall!
Examining the energy efficiency of a single-family house may cost around $525. This provides for assessment of the building envelope and covers missing or displaced insulation, thermal bridging, air leaks, etc.
For a more specific application, such as locating water infiltration through the roof or in a wall, the cost will be subject to a particular estimate.
We thank Alain Corbeil Pro Inspection, a CAA-Quebec approved residential supplier.
Prices and information valid as of December 2010.