IR thermography applied in a proper way is able to detect very accurately temperature difference between air
and surfaces. By means of this tool is now possible to analyse the local instantaneous heat flux through the
surface of a building. In case of steady thermal state, this gives the thermal performance evaluation of the
building envelope. In case of a transient condition an averaging process or a system identification algorithm
must be applied on time-series of such a data. In any case, it is demonstrated that a standard technique based
on thermal flux meter for the thermal resistance (R-value) measurements is more affected by errors than
thermographic measurements using this new approach.
The method is illustrated with experimental results obtained into a residential building. A dedicated
thermographic apparatus is used to map the temperature of the indoor surface of an internal wall and to
measure in same positions the air temperature at 10 cm from the surface. From these data the local heat flux
is detected at any point of the internal surface. A conventional thermogram of the corresponding outside
surface or the outdoor air temperature history allows an easy way to achieve both thermal conductance and
transmittance of the investigated wall.
In this way it is possible the evaluation of both radiative and convective heat flux on a local basis with a
space resolution of 1 cm. The results are here presented within a comparison with the local measurement
with a thermal flux-meter device. These results are important in order to enhance energy efficiency and
comfort in buildings.