Hello Gary, Sorry for the delay in answering but I was away at my daughters and did not have acess to facts and figures.
Iv'e had to blow the dust off them as I haven't used them for years.
The area of the room doesn't really tell you much about the size of rad needed as there are so many other things to take into consideration.
From my tables, if your rad is a single without fins at the rear then its rated output is about 5800 Btus
If it has fins at the back i.e a convector rad then the output would be about7800 Btus.
What I can say is that the U factor for a ventilated wooden floor on joists with lino or similar covering is 0.3 and therfore the heat loss through the floor will be 2016 Btus
The U factor for double glazing is 1.0 and the loss through the window is 1400 Btus.
If the rooms above your lounge are heated to the same temperature as the lounge .then there should be no losses through the ceiling.
Obviously the more wall area to outside ,the greater the losses but losses on inside walls could be zero if it adjoins a room which is heated to the same temperature.
A rad will only give out its rated output if it has a temperature drop of 20 degrees F between flow and return. (Iam still in farenheit as that was what I worked in) . We ran the boiler with a 180 flow.
Alan
