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…
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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.
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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?
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Window AC units are an obvious “solution”, but I can’t have them due to the HOA.
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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!
Not an HVAC tech, but where are your air returns located? I would agree that keeping the fan on will help mix the air in the house. Closing all the registers on the lower floor might stress the system, but you could close a few I’d wager and be safe.
There is a single air return upstairs and the filter has been somewhat recently replaced
We added a return to our upstairs and added an in line booster fan to our HVAC system to move more air up stairs. This helped a lot, but I have to agree that first I would look into insulation as it is a cheaper solution and closing a few downstairs vents as needed.
Close the downstairs registers?
Right here @dingus.
During the summer, close the down stairs registers.
Also yes, if your system can, leave the fan blowing, that way you keep the air circulating.
Our thermostat is downstairs, and this is what we do.
I know multiple people say to close the downstairsregisters, but HVAC sources that I look at say that it greatly stresses the system if you do this and that it’s a bad idea.
You have registers upstairs right? That should provide enough flow so you’re not stressing your system
What are dampers but registers closer to the source?
If you close a register all pipes and joints between the furnace and the register will be under more pressure than designed and can force the joints to cause leaks, this can push humid air into joist spaces as well.
Theres lots of potential issues, putting a damper as near to the source as possible prevents this issue.
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.
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?
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.
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.
Install a mini-split upstairs, it will keep that zone the correct temperature using it’s own thermometer. It can be downsized a bit as the main HVAC unit will help it out using your existing ducting.
For exact design, I would say have one per bedroom or a multi-zone mini-split that can cover each bedroom.
Many (most?) mini-splits are DIY friendly as well, if you want to save a bunch of money and install it yourself.
Just piling on at this point, but we made 2 changes last spring that made summer so much more tolerable in our house.
- More insulation. I bought a cheap thermal camera on Amazon and found entire closets and a bathroom with no insulation. Those rooms are a solid 10+ degrees cooler now.
- More ventilation. Half my house didn’t have any soffit vents, but had attic vents. Adding soffit vents made that half the house 5 degrees cooler all on its own.
And we haven’t found ourselves needing it, but a mini split has popped up a lot here already and is a great idea.
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.
Same issue as you. Second floor bedroom above the garage gets really hot, but we can’t stick a window unit out the front of the house because it would be conspicuous, ugly, and prohibited by HOA.
What I do have is access to the attic part that is adjacent to that room. So what I’m thinking of doing is punching a hole thru the drywall of the bedroom into the attic, mounting a window type AC unit in there so the attic is the “waste heat” side. I would install a drip tray to handle the condensation, and maybe something else to vent additional moisture and heat out of the attic. They make solar powered fans you can install that pull air out the top of the roof.
A better solution in this case would be a split unit to move the heat out of the home envelope completely.
Turn on any upstairs bathroom fans. I find it gives the hot air an escape and allows more cool air to flow upstairs
I use a portable AC - this is different from a window unit. The unit itself stands up inside your room, and it has a flexy hose that goes into a flat panel that’s about 10 inches high and expandable widthwise. You lift the window a bit, put the flat panel in the open spot, then close the window so the light pressure keeps the flat panel in place. It’s all on the indoors side of the screen, so it counts as being inside your house and nobody can complain.
(Assumptions: you have the typical American sliding windows, and your HOA doesn’t have rules about the inside of your house like curtain color or whatever)
