Q: If you have baseboard heating, wouldn’t it a bit of work with heat pumps adding/distributing ducts to all/most rooms in the house.

A: Yes, if you do not have ductwork for AC. If you have the ductwork for AC then the best solution is to connect your heat pump to that duct work. It will then both heat and cool via forced-air circulation, so your primary heating will now be by forced-hot air not forced-hot water. Not everyone likes forced-hot air heating, though I prefer it to forced-hot water because it creates better air circulation. If you do not have ductwork, you can add heat pumps that heat the water for circulating in the radiators. Please see the answer above.

Another alternative to adding ductwork is to install mini-split heat pumps rather than a ducted system. This is what we have at our rental property. Having experience with both ducted and ductless systems I prefer ducted systems. The air circulation is better, the installation cost is lower (if you have the ductwork in place) and the efficiency (COP) is higher, in our case the COP on our ducted system is about 3.0 and on our ductless system is about 2.5.

There are also hybrid solutions where you put new ductwork in the places that are accessible. Usually the first floor is accessible from the basement and so it is fairly cost effective to add ductwork to the first floor from below. Likewise it can also be cost effective to add ductwork through the attic to provide heating/cooling to the top floor. If you do add a heat pump to the attic the attic needs to be well insulated and the heat pump needs to be inside that thermal envelope. If you don’t do this you will be wasting a lot of heat in the attic in winter. This heat will melt snow on the roof and can cause ice dams to form and water leaks that can cause a lot of damage.