You generally still need electricity for radiant heating - there's a pump moving water through the radiators.

But I think it's pretty easy to understand why it's unpopular. First, AC is popular in the US, so a system that can reuse the same ducts is a lot less expensive than something entirely separate. Secondly, it's a lot simpler and cheaper to service. If your hydronic heating system freezes or develops an airlock or springs a leak, you might be looking at five-figure repair costs.

Ever see radiator in action ? The ones I have uses steam. Water would boil in the furnace and pressure would force the steam up to the radiators. Then the steam would condense, heating the apartment and the water would flow back down to the furnace to be re-heated again.

In the old furnace, every so often you would have to add water, depending on how cold it is outside.

Oh, I understand that when AC is present, but in my experience in the PNW - AC is uncommon, but forced air is still preferred for heating.

The air circulation from forced air keeps the mildew down. I once had an apartment with radiant heat. The windows would collect condensed water and the sills were all moldy. Forced air also keeps the CO2 levels in the room in check.

Can confirm, I have radiant heat and we have to watch out for condensation on windows especially in the bathroom or where curtains are drawn. We have an air exchange as well and it does help but not 100%

You can have air circulation independent of the heating, which has the advantage of keeping the mildew down all year round. In fact that's the norm on newly built buildings in France, you have radiators for heating and an active air circulation system.

> I much prefer radiant heat to forced air

I'm curious, why? I've never lived somewhere with radiators, so I perhaps don't know what I'm missing.

I find that radiant more evenly heats a space - there's no obvious warm air flow from a vent like you'd get with forced air. It's also near silent (except for your boiler) and doesn't blow dust about.