The perfect time to conduct a thermal inspection of a flat roof suspected of failure and allowing water to penetrate the substructure is in the summer months. This is because water when heated will hold its thermal temperature much longer than the surrounding roofing materials and therefore can be seen clearly when viewed with an infrared camera.

The summer months offer the best time to ensure that any water laying beneath the top waterproof membrane is sufficiently heated up by the sun irradiation during the day. Then just before dusk when the sun is setting or better still, after the sun has set completely, the roofing substructure will lose its thermal capacity quickly, much quicker than any water that has penetrated. The resulting thermal image will clearly show any water that resides in the substructure and has not evaporated away from the surface.