We have a new house with radiant floor heating. The heat is provided by an air-to-water heat pump. For the most part the system works well. But we have two rooms that never quite get up to temperature. I can get most rooms hotter than we would want (24C), but these two won't go over 21 even with all the other zone valves closed. I'm suspicious that there's a flow restriction. The HVAC contractor feels that the temperature differentials would be greater that what they are (2C) if there were a restriction. There are no flow meters in the system. The contractor is a good guy but he's run out of ideas. Does anyone have any suggestions as to what we should be looking at?