Hi all. I have a 2 storey, ~1200 sq ft home in a hot climate. I have a single HVAC unit…central air and ductwork, electric AC/heat. There is no zoning to the system. The thermostat is downstairs.

Everything is great in the winter months. But in the summer months, the upstairs is absolutely stifling. I don’t have a thermostat upstairs, but it feels like it stays at least 10 degrees hotter than downstairs. I get that hot air rises, but considering the bedrooms are upstairs, it makes things unbearable.

My HVAC air handler and condenser are from 2008, so they are rather old and I’m likely to have to replace them soon. When I do so, I want to figure out how to keep the upstairs more comfortable.

Before I start asking companies for quotes, I want to figure out what I’m doing first. Some things I’ve come across…

  1. Install something like a Nest system with a remote temperature sensor. Place the temperature sensor upstairs and have the Nest use that to figure out when to cycle the AC on instead of the downstairs thermostat. I could install something like this myself instead of needing an HVAC company, though it isn’t necessary very efficient.

  2. Consult with an HVAC company about having dampers/a zoning system installed. From what I’ve read online, it seems like people are saying this isn’t really financially worth it. But if I’m at the point where I want a new system anyway, would it make sense?

  3. Window AC units are an obvious “solution”, but I can’t have them due to the HOA.

  4. I have read of suggestions of people saying to close the vents downstairs in the summer, but it seems like this is bad advice, as supposedly it will stress your HVAC and cause it to fail prematurely.

Edit: Just found a new one…setting the fan on the thermostat to “on” instead of “auto”. Although some people seem to warn of mold growth.

Would love to hear any and all suggestions. Thanks!

  • jo3shmoo@sh.itjust.works
    0·
    5 months ago

    From the “redirect the vents” side of things, I’ve been doing this manually for the 7 years with no ill effects. Last year I added a Flair system and Ecobee to automatically balance using the registers. They have back pressure detection to prevent damage to the HVAC system so there’s always enough vents open. At least in my scenario it’s been a game changer for the third floor of our townhouse. As we’ve headed into warmer months our bedroom is actually cool in the evenings and the lower floors are normal temperatures. During the winter our living space on the second floor was cozy without blasting the bedrooms and making it too hot to sleep. With the number of vents I had it cost just over 1K to do, but that was way cheaper than it would have been to have the house and system rezoned.

    I’m into smarthome stuff so now I’ve actually got room level presence detection going and tying that back to Flair with Home Assistant so we only cool or heat occupied rooms. Wife is a very happy camper in her now temperature controlled office, and it only targets the office when she’s in it.