How did you replace your radiators? Did you have to install ducts, or did you find a cost-effective way to have a heat pump heat the water for your radiator system?
Good ways to upgrade homes that use radiators to use heat pump heating seems like a big gap in the market right now (though, not sure if this is just a market problem or a gap in the technology, since my understanding is that radiators need higher temperatures than forced air systems).
I installed ducts. For me, personally, I think it was worth it. I live in an old home, but someone 50 years ago replaced all of the radiators with baseboard radiators (why???). So ducts over baseboard radiators is a huge upgrade.
Good ways to upgrade homes that use radiators to use heat pump heating seems like a big gap in the market right now (though, not sure if this is just a market problem or a gap in the technology, since my understanding is that radiators need higher temperatures than forced air systems).