Ideas for adding zoning to single HVAC Unit

[Will Adams Jr]

Hi All,

I have a property that has a single family upstairs (3b 1.5ba) with a partially finished basement (3b, 1ba) that I will be finishing and turning into a separate unit. The whole house is on one HVAC system. Additional ductwork will need to be ran to a few rooms. 

I need some ideas for how to zone the upstairs and basement without adding a new hvac system. Any ideas? Some that I have stumbled on and a few notes regarding each:
- Smart-vents (Keen, Flair, Ecovent): The issue with these, is it seems as though they only open and close the vents based on the temperature. This will be an issue with the basement as in winter, simply keeping the vent open will not force additonal warm air out of the furnace. Does anyone know about these?
- New HVAC: $10,000 pill I wont be swallowing if I can help it.

- Electronic dampers: I don't know how these work really, and if the separate thermostat would force warm/cool air.

- Mini-split/wall units: Since I would have to put one ($900) in about 5 rooms ($4500) in the basement to fully separate the systems, this is also a tough solution. I also lose space.

I'm really scratching my head on this one and could really use the help. 

[Kyle Ebersole]

Hey Will, I actually had the same situation in a duplex that my wife and I own and house hacked for a little bit. We lived upstairs in a 3/1 and rented out a 1/1 below. The whole house was on one HVAC system. I looked into smart thermostats and installing sensors everywhere but that didn't work out well. It became a big enough headache as temperatures varied from 1st floor to 3rd floor a lot. Also, my tenants wanted to control the thermostat as it was in their unit and my wife and I wanted to control it. Needless to say, home doesn't feel great when you can't walk into your living room and change the thermostat. I spent $5,000 and had mini splits installed, one of the best decisions I made. All parties are happy and I increased the value of my rental by now having two separate HVAC systems, one for each unit. 

All that to say, I would recommend you install the mini splits. Seems like a big deal now and costly, but you will get that money back very easily if you ever decide to sell the place.