I am adding a bedroom, bathroom, and entertainment room to my walkout basement and am planning on installing hydronic baseboard heat myself while I have the professionals hook it up to my combination boiler Navien CH-210.

I put A LOT of research in and I believe I figured out how much baseboard I should install (please correct me if I’m wrong though) to ensure that I heat my basement enough in the winter months (Rhode Island), but will my boiler be able to handle the addition of a second zone, first one being my main floor?

I plan on installing 36 linear feet of BB in the entertainment room, 12 feet in the bedroom, 6 feet in bathroom, water temp would be 170° at 4gpm (I don’t know how to set the flow rate though, so rate and temp may need to vary 🤷🏼‍♂️)

Below is technical info that may help in answering and sorry for the information over load, I just don’t want to get this wrong lol.

Navien CH-210 ASME

MAWP, Water 30psi

Max water temp 203°

Heating surface 28.6 sqft

Min relief valve capacity 175,000 btu/hr

Min/Max input rating 20,000/175,000 btu/h

264 gph

Entertainment room with exterior door and window 385 sqft

Bedroom with exterior window - with and w/o closet 120/140 sqft

Bathroom with exterior window 64 sqft

Cement slab floor with rug or laminate TBD

exterior walls are cement with 2x4 framing and insulation

Ceiling 2x8 with insulation.