Many many thanks go to our AECB friend, Andrew Pratt at RETANE Thermal Images. He has come over to the Eco Hub with his thermal image camera. The thermal images can identify inconsistency on the thermal envelop.
The contrast could be because of the construction geometry, which nothing is wrong to have, moisture content, emissivity, reflected temperature, atmospheric temperature, distance, heat loss at air/moisture leaks, or missing insulation. The building was not heated for a long enough period (just 8 hours almost for the first time. A heavier structure had not had time to heat up yet) so that it will be very useful to take images again soon at the same positions, well, at 58 locations! The room temperature was just 18.5 degrees. Outside was 9.9 degrees.
Thank you for your detailed advice too, Andrew!