Yes, and that was Canadian houses, I assume, with dozens of vents in the floor on every level of the house. In Europe we mostly see air-to-air heat pumps in co

Yes, and that was Canadian houses, I assume, with dozens of vents in the floor on every level of the house. In Europe we mostly see air-to-air heat pumps in cottages, and there is then only one vent for the entire house. Which if fine and efficient for a small cottage in the fall and spring and maybe a few weekends in the winter. But it would be hopeless in a Canadian winter.