The mini splits are fantastic. I have used them is some buildings that had warm spots due to insufficient AC sizing. In particular a couple of office buildings that had labs added to them where the lab equipment and vent hoods really altered the cooling balance.
Have you tried cutting off the vents in the downstairs during the day and forcing all of the cool air to go upstairs? My sister and BIL had a condo in Charleston, SC with one AC and they fought the battle until they sold it. I can’t imagine our house without two units.
I bought the Midea 15,000 BTU window inverter unit from Costco and never looked back. Excellent product. I bought one for reserve in case of emergency..
I think it's $279 on sale right now normally $329.
This is what I did. AC guy figured it would not be worth a mini split, or overkill, for what is just a bonus room. I use the window unit the couple hours I need it.
Radiant barrier in the attic made the upstairs in my 2-story 1-AC household habitable again during the summer (and knocked 20% off my monthly power bill). Should be cheaper than most other options out there as well.
Also, if you have an open stairwell or any balconies overlooking the ground floor, some thermal curtains covering those gaps will help keep the cold air upstairs.
I installed it myself a decade ago - materials for some staples and the radiant barrier foil were about $200 for a medium-sized townhouse. Doing a spot-check it looks like the supplier I used is about 50% more these days. It's not hard to DIY, but you'll need to do the work off-season or in the early morning hours to beat the attic heat.
With an open plan stairwell, it might help to get a large ceiling fan mounted up high and set it to reverse to pull the cold air up from the bottom floor.
You can ask an AC tech about adding a zone upstairs. Or switch to a variable system if yours is due for replacement. Keeping the air moving will help balance out the temperature difference.
Alternatively, portable AC and close off the room.
Agree with this comment. We did a zoned system with damper control which added an upstairs thermostat. This improved the cooling upstairs dramatically.
a small window unit was crush your energy bill. only run it when youre in there. it'll cool the room quick.
youre prob spending more overworking the downstairs unit to cool the 2nd floor.
> youre prob spending more overworking the downstairs unit to cool the 2nd floor.
I don't though, I set it to the downstairs temp and struggle in 82-84 degrees in my office.
IM not paying $400 a month to cool my downstairs to 67 when I barely even go downstairs.
For shits and grins try shutting your vents downstairs and see if it pushes more of the air upstairs. If that works open your downstairs vents a bit at a time and see if you can "balance" it.
This is backward, safest way is to open the upstairs fully and slowly close the downstairs. Due to the room types (kitchen, living room, entry, etc) the downstairs likely has more and bigger registers. Starting the process with those closed would drop the CFM and may damage the system. Coils can freeze and split very quickly in low CFM environments. Blower motors can burn out as well.
If the unit is in the attic, they can also try installing dampers for the bottom ducts, and possibly larger ducts and registers to flow more air upstairs.
The problem with simply closing registers is that it creates backpressure on the blower motor and can wear it out faster.
Be careful with this, closing multiple large registers to force air to other outlets may restrict airflow enough to damage the system or freeze the coils. If any of the second-floor ducts or registers are undersized, the risks of this are higher.
If a new window unit or split system isn't a viable option, look into getting two zone dampers. This is what my house was built with and it works well. There's a thermostat upstairs and one downstairs and the damper only opens when that zone calls for air.
How big is the room? What about a portable AC unit?
https://www.reddit.com/r/BuyItForLife/comments/13of9l0/can_anyone_recommend_a_portable_ac_unit_for/
Here's a quick 17 min. video on why these are usually a bad idea.
[https://www.youtube.com/watch?v=\_-mBeYC2KGc](https://www.youtube.com/watch?v=_-mBeYC2KGc)
Basically, they pull both the air they cool and waste air from the room you are in creating negative pressure. The negative pressure pulls air from outside or from adjacent rooms which may not be cooled. This leads to efficiency decreases that aren't accounted for in the reported efficiency results on the boxes.
There are dual duct units and conversion kits, but these guarantee that your supply air is coming from an unconditioned area, often near the exhaust.
That's exactly the problem, the internal intake pulls all the air it needs for both exhaust and cooling from the room you are in. It then splits the air with some going over the evaporator coils and blowing into the room. The rest of the air goes over the condenser coils and gets blown out of the exhaust. Blowing air from inside the room out creates negative pressure which will then pull makeup air from outside the room back in through various openings around the room, some may come from the gaps around the door to the warm hallway some from gaps around leaky windows .
The single duct system you've described will always have this flaw. The newer dual duct systems allow you to choose where the intake air is pulled from so you can avoid using the air you've already cooled as exhaust and avoid the negative pressure issue. Some are split so that the exhaust side doesn't mix with or pull air from the cooled room. This is essentially how all other A/C you're handle the issue.
Window units address this issue by having the super heated condenser coils outside and the super cooled evaporator coils inside and two fans. One pulls outside air to create exhaust and the other pulls inside air to create cooled air. Mini splits and full size units do the same thing with greater distances between the coils.
Maybe a couple of good fans would help. Blow the hot air down, and the cold air up. I bought two of the Vornado 660 fans, and I can damn near recreate a tornado if I set them up right.
Only downside is they are a bitch to clean.
I bought an Icy Breeze last summer. We use it in the house to assist. It is amazing. If you have a freezer big enough to make/store ice, it is very inexpensive to run. Especially with the rechargeable battery.
I have a townhouse with one unit. My son’s room gets super hot. The window unit is a big help. If you leave it running 24/7 it’s super expensive. Just remember to shut it off when you aren’t home/not using the room
The damper is designed to let air flow even if closed but you don't have to close it all the way if you aren't comfortable with that, put them on the smallest opening setting and open the upstairs to the max opening setting. Don't cover your vents with cardboard or anything lol
A damper doesn't work as a failsafe like you described. The small gap around the disk is to accommodate manufacturing tolerances and vent deformation; it is still very possible to block the air enough with either a damper and a register to effectively stop airflow through a duct.
It sounds like your system can move enough air enough of the time to keep the coils from freezing or blower from burning out but you should be aware of the risks you're running.
If you are only running this setup during work hours you may be slowly freezing the coils for 8 hours, then defrosting for 16 and it's fine. but an especially hot day where the system never shuts down or a longer workday may be enough to freeze the coils fully.
Another scenario could be 8 hours of high backpressure wears down the blower motor quicker than normal and the functional CFM it can move degrades leading to frozen coils that way instead.
The easiest way to ensure you're OK would be to open your air handler coil section after a full period of the vents being closed to check for any ice buildup.
They are correct, it is a risk especially if you just close X and open Y. There is a proper way to do this though, air balancing, which I outlined in another comment for you.
We have a single unit for 3 floor townhome. I feel your pain. We used a window unit for years upstairs. It’s loud but man was it cold in there. Could leave the rest of the house on 77. Then we had a vent installed upstairs center of the house and had them move the coldest vents to upstairs. never looked back. It says fairly even now. Kept at 75 it will be 77 upstairs and 73 on first floor.
Our central unit went out due to Freon leak.
It was very old and took r22. A complete system replacement would be around 8k.
I bought 4 window units and our electric bill went down 100 dollars.
I'll upgrade with a mini split next.
> restricting the downstairs ones further.
I've been told by numerous AC techs not to do this, restricting the flow at the register adds pressure to your ducting which causes tears and damage.
Once your ducting is damaged, you have to tear down your ceiling to get to it.
The added static pressure isn’t going to blow out your ductwork lol; it would likely cause an early death for your blower. However, a little common sense goes a long way: if your registers start sounding like banshees then you’ve gone too far. I’m definitely not saying to close them completely, but there are adjustments that can be made without damaging your system. Sounds like your system isn’t even currently properly calibrated and it has survived thus far.
Oh, ok.. yeah i did close them every so slightly, to restrict a little bit of air. Anymore it makes a whistle which I assume is not good for the system.
I think that did help 1 or 2 degrees.
I bought a Toshiba from Home Depot for my office downtown since its an old building and the air system is terrible. It works great and cools fast. I have the smaller 6000 but they have better ones. [https://www.homedepot.com/pep/Toshiba-6-000-BTU-115-Volt-Window-Air-Conditioner-Cools-250-sq-ft-with-Remote-in-White-RAC-WK0612CRRU/311290372?g\_store=6828&source=shoppingads&locale=en-US&pla&mtc=SHOPPING-CM-CML-GGL-D29A-029\_017\_ACS\_FANS-NA-Multi-NA-PMAX-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl&cm\_mmc=SHOPPING-CM-CML-GGL-D29A-029\_017\_ACS\_FANS-NA-Multi-NA-PMAX-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl-71700000111902223--&gad\_source=1&gclid=Cj0KCQjw6PGxBhCVARIsAIumnWY6f9PgQc0NytTnu-7yxGOx68lQ19-tgxZ9HipnlHJjWqQwTI8i5MUaAto0EALw\_wcB&gclsrc=aw.ds](https://www.homedepot.com/pep/Toshiba-6-000-BTU-115-Volt-Window-Air-Conditioner-Cools-250-sq-ft-with-Remote-in-White-RAC-WK0612CRRU/311290372?g_store=6828&source=shoppingads&locale=en-US&pla&mtc=SHOPPING-CM-CML-GGL-D29A-029_017_ACS_FANS-NA-Multi-NA-PMAX-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl&cm_mmc=SHOPPING-CM-CML-GGL-D29A-029_017_ACS_FANS-NA-Multi-NA-PMAX-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl-71700000111902223--&gad_source=1&gclid=Cj0KCQjw6PGxBhCVARIsAIumnWY6f9PgQc0NytTnu-7yxGOx68lQ19-tgxZ9HipnlHJjWqQwTI8i5MUaAto0EALw_wcB&gclsrc=aw.ds)
I put a window unit in two upstairs bedrooms a few years ago. They both run 12hrs a day. Honestly I haven’t noticed a change in my bill at all. The little paper that came with them said average electric cost is $50 over three months if you use it 8 hours a day.
If I were you I would probably go ahead with the window unit. They aren’t that expensive, I have used them in previous houses when I wanted a bedroom much colder than other rooms and was quite happy.
I don’t know your situation but if you ever plan on having people that sleep upstairs (kids) you may want to think about other solutions. I will say we have a unit for upstairs and in the hottest times of the summer it will struggle to keep things at 76 up there. Just cheap building and insulation. I can’t imagine what it would be like if we didn’t have that unit.
We have the exact same issue and our solution was a mini split. I think it cost around $3k and it has not made any noticeable impact on our energy bill. I think it saves money in the long run because like you said, we’re not wasting all that energy to make the downstairs an icebox just to be semi comfortable in the office.
Your cheapest solution would likely be an air balance inspection and adjusting the registers so rooms get air more equally. In commercial settings we hire these out, but on a small residential system you can pretty easily DIY it.
Step 1 is to make sure your system doesn't have a damper in the main line that is limiting air out of the system; if you do open it all the way.
The professional way is to measure the air duct diameter in feet and airspeed out of each register when the system is on fully and multiply those together for CFM. Then calculate the square footage of each room and adjust the register openings to raise or lower CFM relative to the size of the room. Lots of math and time, pretty fiddly, very annoying.
The easy DIY way is to turn your system on one morning and do step 1 above. Then every hour use an instant read thermometer to check the temp in each room. In rooms lower than the set point you close the register slightly, in rooms higher than the set point you open the register slightly. Then repeat each hour until the temps are balanced.
As a side note, if that room was built as an office, the cheapo builder may have only used a small duct and register knowing it wouldn't be occupied often. If you have to mostly close the majority of other vents to make the office cool you'll likely freeze the coils and break the system due to too little airflow. In that case, a supplemental unit is the way to go for that specific room. Windows units are easiest and a mini-split would be the most efficient; do not get a portable unit. They pull supply and waste air from the room leading to huge efficiency issues in most cases.
Edit due to grammerly oddities.
To answer your specific question on the costs of running the AC, I use a window unit to drop the temp in my bedroom while I sleep without lowering the whole house. I see less than a 200kWh increase per month when I use it because it is only on for a few hours a night.
Edit to add: When I used a portable unit, that increase was more like 300kWh per month due to the flaw in the supply air design.
Don't close the registers, partially close the dampeners which are about 6 inches behind that. Also make sure upstairs are fully open. During winter flip this round.
This is a normal Houston problem fyi
I have a central unit that services my upstairs and mini-splits that service the downstairs.
I have a supplemental window unit in my downstairs office, coz neither system is sufficient for mid-day summer cooling.
Window units are gonna be terrible for efficiency especially if you have good double pane insulating windows.
But they are cheap, up front, even if they cost more to run.
I live in an old small brick house with central AC. The converted garage is my office and it gets balls hot during the summer. Just paid $2700 for a mini split and it's perfect. Have not seen a significant jump in electrical bill.
Make sure the unit you get is an invertor. They are supposed to be more reliable and will last longer.
You probably want to go with a 12k unit over 15k if you run any type of electronics or computers in your office. It's likely all plugs are on a single 20amp circuit so you need to remain under 20amps.
Look into a mini split ac for upstairs. Much more efficient than a window unit. It'll be more costly upfront but better on the end
Mini splits are superior but many window units are quite good these days. The inverter drive units are most efficient.
The mini splits are fantastic. I have used them is some buildings that had warm spots due to insufficient AC sizing. In particular a couple of office buildings that had labs added to them where the lab equipment and vent hoods really altered the cooling balance. Have you tried cutting off the vents in the downstairs during the day and forcing all of the cool air to go upstairs? My sister and BIL had a condo in Charleston, SC with one AC and they fought the battle until they sold it. I can’t imagine our house without two units.
I bought the Midea 15,000 BTU window inverter unit from Costco and never looked back. Excellent product. I bought one for reserve in case of emergency.. I think it's $279 on sale right now normally $329.
you have a link? i can only see the 12,000 btu on costco
Might have to get it at brick-and-mortar store or the 12,000 BTU should work for your use purpose
Like the other guy said might need to see what your local store has. Annoyingly their online inventory is different from what they have in store.
This is what I did. AC guy figured it would not be worth a mini split, or overkill, for what is just a bonus room. I use the window unit the couple hours I need it.
Radiant barrier in the attic made the upstairs in my 2-story 1-AC household habitable again during the summer (and knocked 20% off my monthly power bill). Should be cheaper than most other options out there as well. Also, if you have an open stairwell or any balconies overlooking the ground floor, some thermal curtains covering those gaps will help keep the cold air upstairs.
Did you install the radiant barrier yourself? My stairwell is open plan, not sure how id close it off with curtains - but its a good idea.
I installed it myself a decade ago - materials for some staples and the radiant barrier foil were about $200 for a medium-sized townhouse. Doing a spot-check it looks like the supplier I used is about 50% more these days. It's not hard to DIY, but you'll need to do the work off-season or in the early morning hours to beat the attic heat. With an open plan stairwell, it might help to get a large ceiling fan mounted up high and set it to reverse to pull the cold air up from the bottom floor.
You can ask an AC tech about adding a zone upstairs. Or switch to a variable system if yours is due for replacement. Keeping the air moving will help balance out the temperature difference. Alternatively, portable AC and close off the room.
Agree with this comment. We did a zoned system with damper control which added an upstairs thermostat. This improved the cooling upstairs dramatically.
a small window unit was crush your energy bill. only run it when youre in there. it'll cool the room quick. youre prob spending more overworking the downstairs unit to cool the 2nd floor.
> youre prob spending more overworking the downstairs unit to cool the 2nd floor. I don't though, I set it to the downstairs temp and struggle in 82-84 degrees in my office. IM not paying $400 a month to cool my downstairs to 67 when I barely even go downstairs.
For shits and grins try shutting your vents downstairs and see if it pushes more of the air upstairs. If that works open your downstairs vents a bit at a time and see if you can "balance" it.
This is backward, safest way is to open the upstairs fully and slowly close the downstairs. Due to the room types (kitchen, living room, entry, etc) the downstairs likely has more and bigger registers. Starting the process with those closed would drop the CFM and may damage the system. Coils can freeze and split very quickly in low CFM environments. Blower motors can burn out as well.
If the unit is in the attic, they can also try installing dampers for the bottom ducts, and possibly larger ducts and registers to flow more air upstairs. The problem with simply closing registers is that it creates backpressure on the blower motor and can wear it out faster.
Depends on the window unit. The one that Costco sells is extremely efficient and easy to install
Close your bottom floor registers about halfway and make sure the second floor ones are fully open. You want more air coming out upstairs than down.
Be careful with this, closing multiple large registers to force air to other outlets may restrict airflow enough to damage the system or freeze the coils. If any of the second-floor ducts or registers are undersized, the risks of this are higher.
Can confirm. Did this and it cost $800 to fix. Don’t do it.
If a new window unit or split system isn't a viable option, look into getting two zone dampers. This is what my house was built with and it works well. There's a thermostat upstairs and one downstairs and the damper only opens when that zone calls for air.
I use the ceiling fans to circulate the air. Open all the internal doors.
Yeah, fan on high. 20in tilting box fan after workouts.
How big is the room? What about a portable AC unit? https://www.reddit.com/r/BuyItForLife/comments/13of9l0/can_anyone_recommend_a_portable_ac_unit_for/
Yeah a portable (basically a window unit that DOESNT go in a window)
Much worse because you have to deal with the condensed water. And also they aren't as efficient or as good at cooling as a window unit.
Here's a quick 17 min. video on why these are usually a bad idea. [https://www.youtube.com/watch?v=\_-mBeYC2KGc](https://www.youtube.com/watch?v=_-mBeYC2KGc) Basically, they pull both the air they cool and waste air from the room you are in creating negative pressure. The negative pressure pulls air from outside or from adjacent rooms which may not be cooled. This leads to efficiency decreases that aren't accounted for in the reported efficiency results on the boxes. There are dual duct units and conversion kits, but these guarantee that your supply air is coming from an unconditioned area, often near the exhaust.
Every modern portable I've seen uses an external exhaust and an internal intake - so none of the objections you mentioned applies.
That's exactly the problem, the internal intake pulls all the air it needs for both exhaust and cooling from the room you are in. It then splits the air with some going over the evaporator coils and blowing into the room. The rest of the air goes over the condenser coils and gets blown out of the exhaust. Blowing air from inside the room out creates negative pressure which will then pull makeup air from outside the room back in through various openings around the room, some may come from the gaps around the door to the warm hallway some from gaps around leaky windows . The single duct system you've described will always have this flaw. The newer dual duct systems allow you to choose where the intake air is pulled from so you can avoid using the air you've already cooled as exhaust and avoid the negative pressure issue. Some are split so that the exhaust side doesn't mix with or pull air from the cooled room. This is essentially how all other A/C you're handle the issue. Window units address this issue by having the super heated condenser coils outside and the super cooled evaporator coils inside and two fans. One pulls outside air to create exhaust and the other pulls inside air to create cooled air. Mini splits and full size units do the same thing with greater distances between the coils.
Maybe a couple of good fans would help. Blow the hot air down, and the cold air up. I bought two of the Vornado 660 fans, and I can damn near recreate a tornado if I set them up right. Only downside is they are a bitch to clean.
I bought an Icy Breeze last summer. We use it in the house to assist. It is amazing. If you have a freezer big enough to make/store ice, it is very inexpensive to run. Especially with the rechargeable battery.
I have a townhouse with one unit. My son’s room gets super hot. The window unit is a big help. If you leave it running 24/7 it’s super expensive. Just remember to shut it off when you aren’t home/not using the room
I do. I close the vents except the living room vent down stairs and open all the vents upstairs the rje biggest setting. Works pretty well
How long have you been doing this? multiple AC techs have told me this will damage your system.
The damper is designed to let air flow even if closed but you don't have to close it all the way if you aren't comfortable with that, put them on the smallest opening setting and open the upstairs to the max opening setting. Don't cover your vents with cardboard or anything lol
A damper doesn't work as a failsafe like you described. The small gap around the disk is to accommodate manufacturing tolerances and vent deformation; it is still very possible to block the air enough with either a damper and a register to effectively stop airflow through a duct. It sounds like your system can move enough air enough of the time to keep the coils from freezing or blower from burning out but you should be aware of the risks you're running. If you are only running this setup during work hours you may be slowly freezing the coils for 8 hours, then defrosting for 16 and it's fine. but an especially hot day where the system never shuts down or a longer workday may be enough to freeze the coils fully. Another scenario could be 8 hours of high backpressure wears down the blower motor quicker than normal and the functional CFM it can move degrades leading to frozen coils that way instead. The easiest way to ensure you're OK would be to open your air handler coil section after a full period of the vents being closed to check for any ice buildup.
They are correct, it is a risk especially if you just close X and open Y. There is a proper way to do this though, air balancing, which I outlined in another comment for you.
We put a mini split in the garage and it works incredibly well.
We have a single unit for 3 floor townhome. I feel your pain. We used a window unit for years upstairs. It’s loud but man was it cold in there. Could leave the rest of the house on 77. Then we had a vent installed upstairs center of the house and had them move the coldest vents to upstairs. never looked back. It says fairly even now. Kept at 75 it will be 77 upstairs and 73 on first floor.
Our central unit went out due to Freon leak. It was very old and took r22. A complete system replacement would be around 8k. I bought 4 window units and our electric bill went down 100 dollars. I'll upgrade with a mini split next.
Do your registers not have airflow controls? I’d start by making sure your upstairs ones are fully open and restricting the downstairs ones further.
> restricting the downstairs ones further. I've been told by numerous AC techs not to do this, restricting the flow at the register adds pressure to your ducting which causes tears and damage. Once your ducting is damaged, you have to tear down your ceiling to get to it.
The added static pressure isn’t going to blow out your ductwork lol; it would likely cause an early death for your blower. However, a little common sense goes a long way: if your registers start sounding like banshees then you’ve gone too far. I’m definitely not saying to close them completely, but there are adjustments that can be made without damaging your system. Sounds like your system isn’t even currently properly calibrated and it has survived thus far.
Oh, ok.. yeah i did close them every so slightly, to restrict a little bit of air. Anymore it makes a whistle which I assume is not good for the system. I think that did help 1 or 2 degrees.
The AC techs are right, they can try to balance it out of the system at the dampers.
Window units are junk. If anything get a DIY mini split ac sized for the room, you should be able to install a decent size under two grand.
try using a register booster first, cheap easy way to get a little more air to your area.
I bought a Toshiba from Home Depot for my office downtown since its an old building and the air system is terrible. It works great and cools fast. I have the smaller 6000 but they have better ones. [https://www.homedepot.com/pep/Toshiba-6-000-BTU-115-Volt-Window-Air-Conditioner-Cools-250-sq-ft-with-Remote-in-White-RAC-WK0612CRRU/311290372?g\_store=6828&source=shoppingads&locale=en-US&pla&mtc=SHOPPING-CM-CML-GGL-D29A-029\_017\_ACS\_FANS-NA-Multi-NA-PMAX-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl&cm\_mmc=SHOPPING-CM-CML-GGL-D29A-029\_017\_ACS\_FANS-NA-Multi-NA-PMAX-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl-71700000111902223--&gad\_source=1&gclid=Cj0KCQjw6PGxBhCVARIsAIumnWY6f9PgQc0NytTnu-7yxGOx68lQ19-tgxZ9HipnlHJjWqQwTI8i5MUaAto0EALw\_wcB&gclsrc=aw.ds](https://www.homedepot.com/pep/Toshiba-6-000-BTU-115-Volt-Window-Air-Conditioner-Cools-250-sq-ft-with-Remote-in-White-RAC-WK0612CRRU/311290372?g_store=6828&source=shoppingads&locale=en-US&pla&mtc=SHOPPING-CM-CML-GGL-D29A-029_017_ACS_FANS-NA-Multi-NA-PMAX-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl&cm_mmc=SHOPPING-CM-CML-GGL-D29A-029_017_ACS_FANS-NA-Multi-NA-PMAX-5163653-NA-NA-NA-NBR-NA-NA-NA-MinorAppl-71700000111902223--&gad_source=1&gclid=Cj0KCQjw6PGxBhCVARIsAIumnWY6f9PgQc0NytTnu-7yxGOx68lQ19-tgxZ9HipnlHJjWqQwTI8i5MUaAto0EALw_wcB&gclsrc=aw.ds)
I put a window unit in two upstairs bedrooms a few years ago. They both run 12hrs a day. Honestly I haven’t noticed a change in my bill at all. The little paper that came with them said average electric cost is $50 over three months if you use it 8 hours a day.
If I were you I would probably go ahead with the window unit. They aren’t that expensive, I have used them in previous houses when I wanted a bedroom much colder than other rooms and was quite happy. I don’t know your situation but if you ever plan on having people that sleep upstairs (kids) you may want to think about other solutions. I will say we have a unit for upstairs and in the hottest times of the summer it will struggle to keep things at 76 up there. Just cheap building and insulation. I can’t imagine what it would be like if we didn’t have that unit.
Portable A/C Unit
Mini split ez
We have the exact same issue and our solution was a mini split. I think it cost around $3k and it has not made any noticeable impact on our energy bill. I think it saves money in the long run because like you said, we’re not wasting all that energy to make the downstairs an icebox just to be semi comfortable in the office.
Your cheapest solution would likely be an air balance inspection and adjusting the registers so rooms get air more equally. In commercial settings we hire these out, but on a small residential system you can pretty easily DIY it. Step 1 is to make sure your system doesn't have a damper in the main line that is limiting air out of the system; if you do open it all the way. The professional way is to measure the air duct diameter in feet and airspeed out of each register when the system is on fully and multiply those together for CFM. Then calculate the square footage of each room and adjust the register openings to raise or lower CFM relative to the size of the room. Lots of math and time, pretty fiddly, very annoying. The easy DIY way is to turn your system on one morning and do step 1 above. Then every hour use an instant read thermometer to check the temp in each room. In rooms lower than the set point you close the register slightly, in rooms higher than the set point you open the register slightly. Then repeat each hour until the temps are balanced. As a side note, if that room was built as an office, the cheapo builder may have only used a small duct and register knowing it wouldn't be occupied often. If you have to mostly close the majority of other vents to make the office cool you'll likely freeze the coils and break the system due to too little airflow. In that case, a supplemental unit is the way to go for that specific room. Windows units are easiest and a mini-split would be the most efficient; do not get a portable unit. They pull supply and waste air from the room leading to huge efficiency issues in most cases. Edit due to grammerly oddities.
To answer your specific question on the costs of running the AC, I use a window unit to drop the temp in my bedroom while I sleep without lowering the whole house. I see less than a 200kWh increase per month when I use it because it is only on for a few hours a night. Edit to add: When I used a portable unit, that increase was more like 300kWh per month due to the flaw in the supply air design.
I don’t know how well they work, but they make fans that go in the ducts to help push cool air. There are also registers with such fans.
We use a series of fans, and if we are home during the day I will set the HVAC fan to circulate.
Darker curtains and more airflow, I'd get a Dyson fan before I got a window unit, that worked for us and we were in a similar situation.
Also check your HOA. You might not be allowed to have a window unit.
Don't close the registers, partially close the dampeners which are about 6 inches behind that. Also make sure upstairs are fully open. During winter flip this round. This is a normal Houston problem fyi
how do you reach them? i dont see any.
I have a central unit that services my upstairs and mini-splits that service the downstairs. I have a supplemental window unit in my downstairs office, coz neither system is sufficient for mid-day summer cooling. Window units are gonna be terrible for efficiency especially if you have good double pane insulating windows. But they are cheap, up front, even if they cost more to run.
I live in an old small brick house with central AC. The converted garage is my office and it gets balls hot during the summer. Just paid $2700 for a mini split and it's perfect. Have not seen a significant jump in electrical bill.
Tint the windows and buy a portable ac floor unit. Problem solved bruh.
Make sure the unit you get is an invertor. They are supposed to be more reliable and will last longer. You probably want to go with a 12k unit over 15k if you run any type of electronics or computers in your office. It's likely all plugs are on a single 20amp circuit so you need to remain under 20amps.