The authors conducted an RCT where the default settings on office thermostats in an OECD office building were manipulated during the winter heating season. Employees’ chosen thermostat settings were observed over a 6 week period. They find that (i) a 1°C decrease in the default caused a reduction in the chosen setting by 0.38°C on average and (ii) office occupants who are more apt to adjust their thermostats prior to the intervention were less susceptible to the default.