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Thermal imaging for damp diagnosis

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For experts like Brick Tie Preservation in Yorkshire (UK), electronic moisture meters, surface thermometers, hygrometers and data loggers, all are standard tools-of-the-trade apart from the company’s own salts analysis and gravimetric testing lab for masonry samples. So, why did it choose to add thermal imaging to its arsenal?

The answer is the ability to see the ‘big picture’ in an instant and to factor in hidden features and defects that have a bearing on the damp problem. These can easily be seen on a thermal image through differences in heat transfer and heat retention.

Brick Tie Preservation’s MD, Bryan Hindle had been interested in thermal imaging for some time and decided to enrol on a thermal imaging course with Thermographic Consultancy Limited (TCL) in Swindon to learn more about the technology.

Next step was to decide on the most suitable thermal imaging camera and as a result of his training, Bryan realised that an entry-level model would be false economy for his business. With expert guidance from Stuart Holland of TCL, a Level III thermographer, Bryan Hindle chose the FLIR T420bx with an additional wide angle lens, as much of the company’s work is performed indoors. Bryan Hindle said. “FLIR T420bx provides the ideal combination of functionality, sensitivity and grip’ type units. Good sensitivity is a particularly important criterion as I can’t count on high temperature differentials and I need to deal with conditions as I find them. Preparation counts for little if, for example, the doors and windows of a building are open when I arrive making the measurement conditions far less than ideal.”

Minimizing Destructive Testing

Although thermal imaging does not directly diagnose conditions such as rising damp, it helps in refining the judgements. This is important as many damp problems are influenced by work carried out in the past which is often hidden behind plaster or other finishes and of which the building owner or tenant may be completely unaware. Thermal imaging helps in making an informed decision on whether time consuming and destructive testing is necessary. For instance, Bryan Hindle was recently able to show a surveyor that a house didn’t require a full damp proof course and lots of work, as the problem was simply one of condensation. He used FLIR T420bx in combination with FLIR MR77 moisture meter, both equipped with Meterlink, a function that allows measurements from the moisture meter to be embedded in the associated thermal image. Hindle added, “I’m able to give my clients an image with dew points and relative humidity overlaid on a colour isotherm taken of the property so they can see the result of the live readings from the moisture meter. Being able to supply the IR image with a clear explanation of what is going on works extremely well.”

Building Knowledge

Apart from being an important aid for diagnosis, FLIR T420bx is also helping to build the company’s scientific knowledge. For example, it was recently used to provide a deeper understanding of how salts can affect the thermal characteristics of masonry and also how saturated air, common in winter, affects rising damp. For this particular project Hindle used FLIR Systems’ patented multispectral imaging technology, MSX®, to help visualise thermal effects. MSX captures visual data from the built-in digital camera and radiometric data from the thermal camera. Internal software then analyses the image and superimposes key elements from the visual image as a high-contrast ‘skeleton’ on the thermal output. “I have also used FLIR Systems’ FLIR Tools to plot some measurement lines to highlight the temperature gradients and plot the maximum and minimum apparent temperatures on each,” Hindle explained.

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