Building and Maintenance
Reduce building costs with infrared thermology PDF Print E-mail
Written by Ian Goldsbrough, InfraTec UK, 2006   
Facilities managers can make considerable savings by minimising a building's energy losses. Of the various technologies that can be applied to do this, one of the most effective and efficient is infrared thermography Buildings that are well run and maintained have a reduced running cost and are more attractive to current and prospective tenants. There are fixed costs involved with purchasing or constructing a building that either cannot be or can only be slightly influenced; however through good facilities management considerable savings can be made on things such as energy costs. Looking for a cheaper provider of energy is one way but large savings can also be made by minimising the energy losses from the building.

The latter is also induced by the respective legislation. Based on the Kyoto protocol from 1997, which aims at the reduction of carbon dioxide and other greenhouse gases, the European Union developed a legislation for the increase of energy efficiency of buildings (2002/91/EG). This is put into national law e.g. by the Low Carbon Building Programme and other building regulations, and will be effective starting at the beginning of 2006.

But still there is the question on how to most efficiently find the areas in which a building loses energy. Various technologies can be applied, of which one of the most effective and efficient is infrared thermography. It is based on the physical phenomenon that objects with a temperature above absolute zero (0.0K or -273.15°C) emit electromagnetic radiation. By determining its intensity, the surface temperature of the emitting object can be calculated without any contact. In countries like Germany, where they have a long track record of reducing energy consumption, infrared thermography has already been successfully established as a leading technology in the market.
 
Problematic areas on a building can be quickly and easily identified using a thermographic camera. With a high-quality camera operating with 360x240 pixels, a field of view (FOV) of some 5.4x3.6m can be seen in one image taken from a distance of 10m with each pixel representing an area of 1.5cm on the building. By increasing the distance from the building, the FOV also increases but this also means each pixel represents a larger area of the building, so small problem areas may not be detected - e.g. at a distance of 20m the FOV is 10.8x7.2m but each pixel will resolve only details bigger than 3cm. These examples show the importance of the number of pixels being scanned for the image quality. High-quality solutions provide some 320x240 resp. 360x240 pixels. There are also thermographic cameras on the market offering 640x480 pixels, which will make the identification of faults a lot easier and more precise.

For building inspections in general, lenses providing a larger FOV like wide-angle lenses have proven to be a plus, for instance making it possible to take an image of a complete house and to take images inside the house with a good FOV. Using a camera offering the opportunity to change lenses or apply optical adaptors will increase the number of applications for which the system can be used, as do special lenses for normal photographic cameras within the visible spectrum of light.

Besides the geometrical resolution, the thermal resolution is important for thermographic measurements but it is especially crucial with building inspections. As insulation problems in Europe will mostly result in a loss of heat, at those areas they will appear warmer than the neighbouring outside areas (Figure 1) resp. colder than the neighbouring indoor areas (image 2).

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Figure 1. Leaking window with warming effect
on the outside of the building. 		Image
Figure 2. Poor insulation of outside wall.

Detection of these problems using a thermographic camera is far easier during the winter months because the temperature difference between the inside and outside of the building is greater. However if a high-quality cooled thermographic camera, which can detect temperature differences as small as 30mK, is used it is possible to carry out building inspections at other times of the year. This will mean that the payback time on your capital outlay will be much shorter with the equipment being used throughout the year. A procedure that is used to help detect where there is an air leakage problem with a building is the so-called Blower-Door Test. To perform this test, all external windows and doors are closed and air is blown into the building through one of the doors. This creates a pressure difference between the inside and out of about 50Pa. This will mean that air from the inside will pass through any areas that are not airtight, cooling down those areas and thus making them easier to detect with a thermographic camera (Figures 3 and 4).

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Figure 3. Thermogram without Blower-Door
Installation. 		Image
Figure 4. Thermogram with Blower-Door Installation.

With uncooled devices operating with a microbolometer detector, the thermal resolution is not higher than 80mK, normally expressed in the term Noise Equivalent Temperature Difference (NETD), which implies that temperature differences as small as 80mK can be detected (Figure 5). Although this seems to be a low value, images taken with such a camera are clearly distinguishable from those taken with cameras specifically designed for building inspections that operate with cooled detectors. The cooling enables the application of more sensitive detectors, providing NETD values of down to 30mK, which results in a much sharper image (Figure 6).

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Figure 5. Thermal image taken with uncooled
microbolometer camera. 		Image
Figure 6. Thermal image taken with cooled scanner camera.


Taking excellent thermal images is the first step towards a sound analysis of the thermal behaviour of the scanned building. Applying high-quality cameras or hiring service providers using such equipment is very important. Based on the images taken, the actual analysis of the data can be done using the respective software. Within a good-quality software package there will be features to make the analysis of the images much easier like automatic hotspot or coldspot detection plus many more. Different colour palettes and automatic isotherms indicate areas of heat loss on the spot (Figure 7). The software might come with integrated report generators but a drag-and-drop function to transfer the output of the analysis into other Windows programmes like Microsoft Word will serve the same goal - an easy way of producing effective reports for further maintenance operations.

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Figure 7. Screenshot of analysing software.

Having concentrated on insulation problems to be found using infrared thermography, it should not be forgotten that the other applications of this technology can be useful for FM. These could be monitoring of electrical installations (Figure 8), leakage location (Figure 9) or the location of damp areas that could lead to the growth of mould. (Figure 10).

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Figure 8. Switchboard cabinet. 		Image
Figure 9. Heating leake.


These application examples will only give you an idea of the opportunities infrared thermography will provide. As there are many more applications plus a lot of application specific know-how, please do contact the technology specialists to help decide the best solution. This will help to prevent you from going down a route that's seemingly cheap but actually expensive, so infrared you can use thermography to save money and not to spend more.

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Figure 10. Cold corner with tendency to moulder.

 
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