Zoned heating system very warm even without heat on upstairs?

Question

I know heat rises, but our 1st story floorplan house gets pretty darn warm during the winter months. Other than turning on the AC or opening windows in the upper story zone, anything else that could be done? The majority of the square footage is downstairs and there is only one small stairway leading upstairs.

Forced air heat, supplies overhead. Upstairs is a separate zone. Displacement of sqftage is about 600 upstairs, 1800 downstairs. There are 2 zones, upstairs and downstairs. The downstairs is set to 70 in mornings, but gets up to 75 degrees upstairs without running heat up there. For the upstairs, there is one return air vent in the main rec room. Downstairs there are two in the hallway and master bedroom.

Answer 1

Shutting some internal doors might help. Especially the door to the room upstairs with the return vent, to avoid pulling hot air upstairs. Anywhere air can get out upstairs (e.g. bathroom extractors, trickle vents) can encourage convection too.

If there's heat in the downstairs hallway you might want to restrict it. I have had to do this with our (wet) heating system otherwise the master bedroom gets too hot. Heat from near the bottom of the stairs goes straight up. You may need to improvise, at least for testing.

Ceiling mounted warm air vents and their ducting have to be well insulated to avoid acting as underfloor heating for the floor above, and yours probably aren't. Feel the floor and you may be able to tell where the ducts run.

Answer 2

If the upstairs is truly another zone there should be a separate damper to close it off or reduce the flow.

Zoned means you have separate control over different areas.

Sounds like you either need to adjust the existing damper or install one.

Good luck!