We live in a 1914 house. There's 2 returns on the main floor. We end up with a wide gap among the floors (basement to 3rd floor). I looked into systems that

We live in a 1914 house. There's 2 returns on the main floor. We end up with a wide gap among the floors (basement to 3rd floor). I looked into systems that have inflatable bags that block the areas that are warm so the other areas can get more of the hot air. Something like this: https://www.retrozone.com/Catalog/flexdamper/Pumps.htm https://www.retrozone.com/Catalog/flexdamper/Pumps.htm I didn't end up doing it and I don't know anybody who has. And it's probably a lot more expensive than opening your window in the winter.