I checked on the tiny house this morning to see how the thinset was curing and to make sure that the floor wasn’t too cold. It went down to -16 C (3 F) last night and the thinset needs to be at least 10 C (50 F) to cure properly. The floor seemed to be curing but was still a little cool to the touch so I turned up the heater. The windows and parts of the door were covered in condensation. The condensation on the lock and door handle had frozen. I do indeed need a heat recovery ventilator to for ventilation in the winter. I didn’t have my camera with me to take pictures when I went in at first, so the photographic evidence isn’t quite as spectacular as it was when I first went in.