18 C O N T E X T 1 4 9 : M A Y 2 0 1 7 particularly when needing to capture a whole facade. Sometimes it is also necessary to use a wide-angle lens. Occasionally images have to be stitched together, depending on the size of the building. The cost of cameras rises significantly in line with increases of the resolution, and with the addition of any accessories, but there is no substitute for having the right equipment for the job. One great advantage of using thermography during retrofit is for communicating what has been done. Capturing the whole facade before and after insulating is a great way of visually highlighting the improvements that have been made. More detailed and close-up images are also useful for identifying any gaps and subsequent thermal bridging. When interpreting thermal images taken inside the building, colours representing cold areas are an indication of heat loss. For external thermal images, it is the colours representing warm and hot areas that are an indication of heat loss.These areas of heat loss can be either expected as part of the design, or unexpected and indicating a potential problem. Issues could include inappropriate installation, poor workmanship or other unforeseen consequences. To demonstrate the use of thermography as part of a retrofit project, the following example illustrates a traditional solid-walled house after receiving retrofitted external wall insulation (EWI).The independent survey was undertaken as part of the monitoring element of the energy efficiency improvement programme. The house, built pre-1919, is of traditional construction. The design of the EWI installation was undertaken by the system supplier and commissioned by the principal contractor.While the overall aesthetics of the house appeared to have been improved, primarily due to the whole-street approach taken, a closer look under the surface and at critical junctions tells a slightly different story. The images shown here are a corresponding thermal image and photograph of the internal surface of an external wall after the EWI had been installed. The blue colour of the wall in the thermal image indicates that the surface is colder than the surrounding surfaces and the ambient air temperature. From the naked eye and the photograph it was not possible to identify this anomaly. However, an external thermal image and a discussion with the home owner did suggest a possible cause. The thermal image of which a detail is shown on the front cover of this issue of Context illustrates the external facade of the dwelling.The thermal image appears to confirm the resident’s claim that water was pooling on the first floor window sill, and was travelling down behind and penetrating the EWI. Jo Atkinson, an architectural technologist and qualified thermographer, leads the Carbon Trust’s housing-related work. An internal photograph of an external wall (Images: Jo Atkinson) An internal thermal image of that external wall
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