Looking to add panel radiators to existing cast iron gas boiler and radiator system

todddos

Hello, I own a fully connected townhouse in Queens, NY. Top 2 floors (~1500 sqft) are heated by the original cast iron radiators and a relatively new cast iron gas boiler. I'm renovating the basement floor that currently has no heat and houses the boiler and main supply/return lines for the 2 floors above. The home is on a steep grade, so the basement is entirely above grade at the rear of the home and ~75% below grade at the front. I'm looking to add ~4 panel style radiators to the system in order to heat this floor.

Curious on suggestions of how to most affordably and simply do this. I do not necessarily need the floor and the new radiators to be on a separate zone. The will have thermostatic valves individually and should provide sufficient control. It has been suggested that I add a set of Venturi T's right at the boiler. The radiators that need to be fed will be ~ 5 ft. beneath the main supply and return lines, so it's been recommended to not T off from those lines, as the water will get trapped in the radiators and not have sufficient pressure to make it back up and to the boiler.

Questions:

- Where exactly should I put the verturi T's? I know right at the boiler, but on the supply line or the return line. And if supply line, should I place them before or after the pump?

- If Venturi T method is the simplest way to go, how do I size them? And how many do I need?

- Can I mix low mass panel radiators (Beacon Morris Series 21) with the existing higher mass cast iron radiators in the rest of the home?

todddos

Pictures attached show my current boiler setup. Boiler is one of these... http://newyorkerboiler.com/products/gas-boilers/cg-f-water-series-boiler/

Ironman

What kind of piping method is currently employed on the rest of system?

Have you done a Manual J heat loss calculation on the downstairs to determine how much heat is needed?

Pics of the existing piping would help.