New emitters for a steam system

D107

My cousin lives in Queens, NY and is redoing his two-story 'townhouse' I guess you'd call it. A row of 5-6 connected houses serviced by one steam boiler. Some walls taken down, bathroom added, etc. Existing rads are cast iron. He's being advised to use cast iron baseboard. He reports that most of the radiators in the house have never had to be turned on, even after the basement mains were insulated some years ago. Not sure if risers are visible or not.



The issue is how does one size new emitters for a system like this, where one likely does not know the connected load of the other apartments? He should obviously find out the specs of the existing boiler and find out if it's set up correctly for pressure, etc. If it's set up wrong and overheating, and he bases emitters on that, there might be issues down the road with a new boiler or corrected settings. Seems like a new heat loss would help. Since I love cast iron rads, I'd probably keep what's there and put TRVs on them and replace any non-working shutoff valves, but there's routing issues due to some new room configurations.