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!

  • Death_Equity@lemmy.world
    8·
    5 months ago

    The mini-split route idea is a great solution, but I am wondering if you have an unvented or poorly insulated attic that is a contributing factor to your problem. If your attic space isn’t setup properly and you throw a mini-split at the problem, it is sort of like pumping water out of a boat without fixing the leak that is flooding the boat. Even something as “simple” as a powered attic vent could help in HVAC performance and operating costs. If the hot air can’t vent or your insulation is inadequate, it just stacks down and heats the top floor.

    The other thing I would be looking at is if the HVAC run up to the second floor is done properly or if the dampers are not right. A house that size really shouldn’t have much trouble if everything is balanced right.

    Closing vents on the first floor and leaving the second floor open will increase the wear on the fan and may decrease efficiency if not enough air can be moved through the open vents. Knowing how bad an idea that is would require some measurements and math.

    Having the nest with a second temp sensor would just force your HVAC to work harder to cool the upstairs. The single sensor nest can be a smart move to reduce costs with the higher degree of control.

    Having dampers installed does more or less the same thing as closing vents, but with a higher cost. A zoned system is expensive and kind of silly on a house of that size.

    • dingus@lemmy.worldOPEnglish
      2·
      5 months ago

      The mini-split route idea is a great solution, but I am wondering if you have an unvented or poorly insulated attic that is a contributing factor to your problem. If your attic space isn’t setup properly and you throw a mini-split at the problem, it is sort of like pumping water out of a boat without fixing the leak that is flooding the boat. Even something as “simple” as a powered attic vent could help in HVAC performance and operating costs. If the hot air can’t vent or your insulation is inadequate, it just stacks down and heats the top floor.

      Unfortunately, I don’t live in a free-standing house. It’s a townhouse, so it’s connected to other units so I don’t think that I can make changes to the attic.

      The other thing I would be looking at is if the HVAC run up to the second floor is done properly or if the dampers are not right. A house that size really shouldn’t have much trouble if everything is balanced right.

      I don’t seem to have any dampers at all as far as I can tell.

      Having the nest with a second temp sensor would just force your HVAC to work harder to cool the upstairs.

      Yeah, I get that I would be pushing the HVAC system to simply be on more, but at the very least I could actually set the temperature upstairs instead of having it fluctuate so wildly. Often, I’ll set the temp low at night to be more comfortable. It’ll be to the point where I’m basically freezing with the sun down. But then in the morning, when the sun rises it’s unbearably hot.

      The single sensor nest can be a smart move to reduce costs with the higher degree of control.

      What do you mean by this?

      Having dampers installed does more or less the same thing as closing vents, but with a higher cost. A zoned system is expensive and kind of silly on a house of that size.

      So there’s no real reason to get dampers installed then?

      • Nougat@fedia.io
        7·
        5 months ago

        If you’re in a townhouse, you have an association. The association would be responsible for the common attic and its insulation. Bring this concern to the attention of the board. Could be other people have the same problem and the fix could be attic-related.

        • SchmidtGenetics@lemmy.world
          4·
          5 months ago

          Most town houses have fire walls up to the roof, so it’s your own liability and issue as it’s not a common space.

      • Death_Equity@lemmy.world
        4·
        5 months ago

        You would have to get a GC out to inspect the attic and then give you a written recommendation of alterations, which you then would take to your association. Talk with your neighbors and see if they have the same issue, them jumping in on the issue would offer a greater chance of approval. It is possible the association may pay for it if the problem is attic venting, insulation would likely fall on you.

        Forcing the system to run more to compensate for the upstairs would drive up your electric bill and may not actually help if the problem is in the attic or balance of the HVAC. You could set the temp lower at night to accomplish the same thing as dual sensors, but you still are just throwing money away that should be better spent on addressing the issue directly.

        Having a nest vs non-smart thermostat allows you to set schedules in a smarter way than a regular tstat.

        Having dampers allows you to balance the system so the downstairs gets less air than the upstairs, instead of you having to go around closing vents and the downstairs would be cooled better than just shutting vents and sending most of the air upstairs.