| Driven by rising energy costs, building regulations and | | | | is needed. |
| Carbon Emission Reduction Targets (CERT), | | | | External or Internal Survey? |
| thermography of building envelopes is the fastest | | | | The choice of survey approach does not stop there. |
| growing application of thermography. The intention of | | | | The next question is should the survey be carried out |
| this article is to inform potential customers of the | | | | externally, internally or both? |
| various approaches to building thermography and | | | | An external survey, invariably is the simplest approach |
| provide an understanding of the benefits and limitations | | | | to implement. It is relatively straight forward to capture |
| of each of these approaches. This will enable the | | | | thermal images of all of the building envelope, whereas |
| reader to specify the type of survey they require to | | | | images captured internally require the walls to be clear |
| meet their desired outcomes. | | | | of furniture, pictures and other equipment, if confidence |
| Qualitative or Quantitative? | | | | is to gained from the survey. On the face of it then, an |
| Approaches to building thermography can classified | | | | external survey would be the best approach to |
| under two categories; qualitative and quantitative. | | | | implement. |
| Qualitative approaches rely on the thermographer's | | | | However, it may be the simplest, but it may not give |
| knowledge and experience of thermography and | | | | the desired results. An external survey is very much |
| building science to identify potential defects with a | | | | affected by the environmental conditions at the time of |
| building envelope. This approach does not rely on | | | | the survey, clear night skies and windy conditions |
| temperature measurements but rather the differences | | | | make any kind of quantitative survey far too |
| in the levels of radiosity (differences in colours shown | | | | inaccurate. Also, depending on the building construction, |
| on a thermal image) to ascertain areas of excess | | | | not all building defects will be evident from images |
| heat loss. Whereas quantitative approaches use the | | | | taken externally, e.g. poorly fitted loft insulation in a |
| same approach to identify the defects but go one | | | | house with a pitched roof, can only be detected with |
| step further and use the temperatures measured to | | | | an internal survey. |
| ascertain how much heat is being lost. | | | | Conversely, an internal survey is less affected by |
| The type of approach used will therefore depend on | | | | environmental conditions, as air temperature and |
| what it is you are trying to achieve. If you are only | | | | convective currents are relatively constant making |
| looking identify the defects within the building envelope, | | | | quantitative assessments more accurate. But internal |
| then a qualitative survey will deliver the desired results, | | | | surveys are far more time consuming, with many |
| however if you are looking to identify potential cost | | | | more images needed to be captured due to the |
| savings/CO2 reductions, then a quantitative approach | | | | number of floors/rooms and limitation of the lens angle. |