You have a newer house that's "open"? No doors? In older houses you could control what rooms were warm by opening and closing doors. New houses are beautiful and airy but we pay a price for high ceilings and an open floor plan.
We can open and close doors and also the heater vents. They have a little
arm that can adjust the amount of air blowing through them to near zero.
The sun room has double doors, and we just close the vents and the doors.
We have too many windows, and in spite of their being double paned, the
cold comes through on those -18° nights. Well, we only had one so far...
But anything under 10° is dang cold. Heck, when it’s up in the high 20°s,
I go out in a sweater and my house shoes because it feels warm, LOL!