I need to provide the builder of my new house the height from floor of the water connections for the radiator of my bathroom.
Right now I have a 1800 x 3100 mm bathroom with a "design radiator" (the tall ones where you can hang towels on multiple levels). The radiator is 500 x 1150 mm (taller than wider). The connections for the water are at the top, at 1920 mm height. Above the bathroom is the roof (plus an empty cold space for storage), below the bathroom is another bathroom.
My new bathroom will have a living room below and a heated attic above it, therefore less heat loss, but is 16% bigger: 1800 x 3600 mm.
In both cases the radiator must be located on the long wall next to the door.
Using the values from a shop, I estimate that my current radiator (500 x 1150 mm) should provide about 650 W at 75C water temperature (there are products with the same size and 550-750 W, plus one 435W quite similar to my current one). It is set usually to a bit less than half power, but I admit the actual water temperature in my building is unknown to me, but it's quite hot at the touch of the pipes. In the new house the water temperature will be lower, given the use of floor heating.
I guess I can use a similar radiator, but how can I estimate more accurately the power (and therefore the size) required for the new one in the new house?
After knowing the height of the radiator, I have to choose the position of the water connection. The height is more or less fixed to be easily accessible, but I can choose between water connections on top of the radiator, or on the bottom side. Which one is preferable?