Hi. I'm looking for some information regarding radiator size/btu/quantity. In a new build, should the builder provide the radiator size/btu on the room size only or, the room size (3×4mt), ceiling hieght, how many windows and how many outside walls? I'm in a new build with the lounge the depth of the house. One triple payne window at one end and a double payne at the opposite side. Three outside walls. The builders have put 1 radiator under the three payne window only. The back of the room never gets warm, only the first 3rd of the lounge infront of the radiator. I worked it out with the full measurements. I would need over the btu of the one radiator, should the builder have know this and added a second radiator at the other end of the room to add up to the btu required? Any building regulations regarding this please? Any advice gratefully appreciated.