This paper describes results of a numerical simulation and an exergy analysis focusing on the influence of piping thermal insulation on thermal comfort and resource consumption related to hot water floor heating during night time. In a case, pipe length is 1m indoor and 4m outdoor, changing from polyethylene foam 10mm to urethane foam 30mm can reduce warm exergy consumption within the pipe from the boiler to the inlet of the floor in 68%. At the same time, the seasonal median of the room air temperature at am 6:00 can be raised from 15.5°C to 20.0°C. Improving thermal insulation of piping increases radiant and convective warm exergy from the floor two times and four times, even if hot water temperature at the outlet of the boiler is the same.