Final little demo of my new thermal camera is looking at the ceiling of the front room many hours after the heating has turned off. The FLIR One's camera is, as you've no doubt noticed, very low resolution, about 160 x 120. It also has a frame update rate of no better than 15 fps even when using the unofficial (paid) Android app I'm using below which unlocks quite a few features imposed on the device by US military technology export restrictions (I'm in Europe, so those don't apply to me, but the manufacturer which is US based must comply. Thankfully a kind German wrote an app to bypass the software based imposition of US law on non-US citizens). And note that even after many hours after the heating went off, there is an obvious "hot" bar running across the ceiling which is a bit of a surprise to us because there are no radiators anywhere on that side of the house. Despite the low resolution, the sensor is really great at picking out fractions of a degree in temperature difference, so an only one or two degree difference looks really severe below. Our best guess is maybe piping to a back boiler behind the open fire which is no longer in use? Anyway, I've confirmed the warmth via hand touch, it's definitely there.