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Thermography, a quick and simple imaging technique, serves to determine remotely and contact-free the temperature of a given object. When applied to a city, this technique is used to identify, for each building (whether public or private) within a given zone, the amount of heat loss.

Thermography: Emphasis on saving energy and reducing the greenhouse effect

All residents of the municipality being studied are entitled to know the level of heat loss of their residences and whether their dwelling is adequately insulated or instead whether they should be advised to proceed with insulation works.


To obtain a comprehensive diagnosis of a building, two types of thermography are combined:

  • aerial thermography, which serves to visualize energy losses emanating from roofs;
  • land thermography, or so-called facade thermography, which serves to visualize the heat losses emanating from building facades (walls, doors, windows, etc.).

How is aerial thermography conducted?

To measure heat losses from roofs, a plane equipped with a photo hatch housing an infrared scanner flies over the territory at relatively low altitude (400 meters) in order to obtain heat loss images. The measurements are recorded at night while making several passes.

Did you know?

During the measurements, so as not to bias the data, residents are requested to:

  • keep the temperature in their dwellings at approx. 19°C, as an overly high or low heat setting alters the interpretation of results;
  • refrain from opening windows to glance at the plane.

How is land thermography conducted?

A building facade thermography is performed by means of an infrared scanner placed on-board a dedicated vehicle that travels along the streets at night so as not to interfere with traffic.

By traversing tens of kilometers at night, this innovative method is thus able to complete a thermography at the scale of a municipality or an entire metropolitan area, which in turn reduces the per-building cost.

The acquisition system developed by LNE features equipment like nowhere else in France for facade thermography applications:

  • a tried and tested infrared scanner,
  • a laser profilometer used for the 3D reconstitution of buildings,
  • a geo-referencing system incorporating GPS receivers,
  • an inertial platform and odometer to measure the distance traveled by the vehicle,
  • a data acquisition and control computer unit.

Did you know?

The laboratory vehicle is inserted into city traffic without causing any disturbance.

How are results presented?

Upon completion of the thermography, results are translated into a color-coded format. Buildings are classified into 5 heat loss levels, ranging from class 0 (no heat loss, i.e. unheated building) to class 5 (sizable losses).

By applying these results to the corresponding documents (city maps, parcel plats, aerial photographs, etc.), the municipality under study generates a complete thermal mapping of the city, with a possible close-up on each dwelling. The local public works office and individual homeowners are thus given a decision-making tool to undertake insulation works deemed to be a priority.

In the case of a facade thermography, results are superimposed onto a 3D reconstitution of the buildings produced by LNE.

What exactly is heat loss?

Répartition des déperditions de chaleur dans un logement

Heat loss refers to all instances of calorie leakage (or losses) detected on a building. Such losses tend to be concentrated on the roof and facades of a dwelling.

30% of the heat losses on a building with no or insufficient insulation originate via the roof, and another 25% via the facades.

When a dwelling is not insulated or only poorly insulated, these heat losses are significant and lead to excess energy consumption along with high heating bills. This surplus consumption also produces greenhouse gases, which further contribute to global warming.