I observe consistently 2C higher when inside the bottom triangle with the sensor facing out compared to hanging beside the wall on the cable. This is compared to my commercial programmable thermostat on the same wall. They match when out, 2C higher when in. There was some discussion of this elsewhere on the forum too. This isn’t just when the pi is working hard, but all the time (for example at 2% cpu load and 36C CPU temp.) I’ve added a Samsung S4 as an “external sensor” in the same location, also 2C lower.