Here at Camera Obscura you can find a (newly-updated) heat camera, which allows a unique view of your body by using infrared rays.
(reference: author’s own)
Many of you may have already experienced our heat camera, but those yet to see it have something to look forward to. But what you may not realise is that infrared imaging (thermography) can be used as a method of assessment when conducting building surveys. In essence, by seeing the infrared image of a particular wall, doorway or window can highlight otherwise unseen conditions, thus bringing to attention any potential problems.
(reference: Historic Scotland)
What is thermography?
Thermography is the visualising of temperature across a surface, which is non-destructive, through the use of a thermal imaging camera that detects infrared radiation (IR). IR cameras work outside the visible light spectrum (which is 0.4-0.76 μm) but within the infrared light wavelengths of anywhere between 2 μm and 14μm 1
What can we use thermography for?
Well, aside from the spectacle of viewing the hot and cold spots on your face and body, thermography can be used in electrical inspections, military operations, medical or laboratory environments, finding the path of heating pipes underneath your floorboards, detecting areas of moisture or water infiltration on a building surface, detecting areas of heat loss through a building façade or assessing how well insulation is performing in roofs. 2
(ref: Historic Scotland)
In building surveys, it is often advantageous to overlay an image from the thermal camera on top of a regular photograph, to give a visual context of where the thermal image was taken.
(ref: HS again)
How to undertake a building survey (with thermography)
It is necessary to heat the room to be investigated before undertaking a thermography survey, in order to achieve the best results. In normal conditions, there would be little temperature difference along any given surface, so heating the space for a recommended 24 hours beforehand is advised3. By creating a larger temperature difference between inside and outside allows evaporation of moisture to occur and the passing of heat through surfaces. The bigger the difference in temperature, the better the result will be.
Once the images have been taken, usually the presence of dampness and moisture can be seen immediately, or if imaging roof structures, areas where excessive heat is escaping are easily detected.
The majority of thermal images, such as those produced by our thermal camera, use the ‘rainbow’ method of coding, whereby hottest areas are red/white (hence the term red hot) and the coolest areas are blue/black. This code helps to highlight areas of moisture. Other codes include ‘iron’, which is normally used when analysing energy efficiency through heat loss, or a simple greyscale, from black to white.
(reference: author’s own)
There is a wealth of information out there on this topic, and it this blog entry is a mere summation of thermography uses outside of Camera Obscura & World of Illusions. Thanks must be given to Maureen Young from Historic Scotland who gave a great presentation on this rich topic of thermography in building surveys at the Heritage Research Conference provided by Historic Scotland and RCAHMS (Feb 18th-19th), which acted as a catalyst for this entry.
Written by Mathew Reilly
Footnotes/references for text:
1. Young, M.; Thermal Imaging in the Investigation of Solid Masonry Structures; The Building Conservation Directory 2014 (Cathedral Communication Ltd.: Wiltshire, 2013), pp 46
2. IBID, pp 46
3. IBID, pp47