Sizing Window AC for Small Rooms

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dboeger1
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Sizing Window AC for Small Rooms

Post by dboeger1 »

We bought our first home last year. It's a modest older home without AC. My original thought was to get professionally installed AC, but after living here for almost a year, I've realized the home isn't particularly built with AC in mind. I've concluded that it's probably significantly easier and more cost-effective to start with smaller window units for the 2 smallest bedrooms, which get by far the most sunlight and are many degrees hotter than the outside air and anywhere else in the home. We're in San Jose, CA, so the weather is relatively mild most of the year, but we do get some really hot 100+ F weeks most Summers. I have not measured, but I suspect those 2 rooms regularly hit 100+ F even during milder weeks, and are pretty much uninhabitable on the hottest days.

Both rooms are approximately 100 square feet, so quite small and well within the stated bounds for 5000 BTU window units. However, I do not have experience buying window AC units myself, so given how hot those rooms get and the fact that the exterior part of the AC units will be under the beating Sun outside, I'm wondering if 5000 BTU is sufficient. Some reviews state that the 5000 BTU units struggle to cool rooms on hot days, but I don't know if that's just reviewers installing them incorrectly or in larger rooms than they're intended for. My understanding is that the window units are more efficient when running consistently as opposed to turning on and off. However, comfort and cooling ability is top priority for me as one of these rooms is going to be a nursery soon when our first baby is born.

Here are the options and approximate prices I'm considering:

1) 5000 BTU. The obvious choice for smaller rooms. I can get decently rated units for about $140. The Frigidaire I would prefer for having the R32 refrigerant is like $160, but I've seen it dip as low as $125, which I would have bought but was sold out by the time I got back home.

2) 6000 BTU. There are a number of cheaper brands with 6000 BTU units for not much more, approximately $180 I think. I suspect these would work well enough given the high temperatures of the bedrooms. I just don't know if it's worth getting a cheaper brand just to get some more BTU which may or may not be necessary for the room.

3) 8000 BTU. Costco's web site in particular has an 8000 BTU HiSense unit for $200 which is well below the standard price range for such units, so it seems like a screaming deal. However, again, I have not tried an 8000 BTU unit in a small bedroom before, so I have no idea if this is actually too much and would suffer from inefficiencies due to using on a room that is too small. Does anybody have relevant experience?

4) Wait for a deal. We're willing to wait for a sale, but the obvious one, Black Friday, may be too late. The baby is due at the end of October, and I'd really prefer to get something installed before then. The weather should be cooler by then, but again, these bedrooms trap a lot of heat, so if Summer runs late, our baby's going to be quite uncomfortable. Can we expect any obvious AC sales before then? Could these be impacted by pandemic supply chain issues?

5) Horizontal window units. All our windows slide horizontally, so we need to spend a little extra to set up standard window units to work with them. Frigidaire has some horizontal window units, but they start at 8k BTU and are quite expensive. I may splurge on the largest one for our living room, but I doubt it's worth it for the smaller bedrooms.

Note that I'm not really considering the portable hose units at this time. The floor space in these rooms is already quite limited, and we need to be able to pull blinds or shades or whatever over the AC which the hose will not allow (no window coverings installed yet, those will be done soon). We actually have a portable unit that we are using in the room currently. We picked it up for free from someone who was moving out of state last year. It's a 10k BTU LG unit. From my research online, it looks like it's 6500 BTU equivalent by DOE standard, and it struggles but does barely cool the room sufficiently while running continuously, but with one critical flaw, which is that the stupid flat piece that goes next to the sliding window isn't long enough for our window, so there's a small uncovered square opening in the top corner of the window. We also haven't bothered taping it up or anything, so basically, this room is not airtight at all. I suspect if we got a properly sized plexiglass cutout and put foam or other insulation material in all the gaps, it would probably work a bit better. I'm not sure how my experience with the portable unit would translate to a properly installed window unit. It has me worried that 5k BTU is not enough, but again, that might just be the poor setup we have now. And when I say it cools the room, yes, the air temperature will drop very gradually over a lengthy amount of time, but the memory foam mattress in particular still seems to feel hot and radiate a lot of heat. I still get sweaty laying in bed despite the air feeling nice and cool, and I doubt this portable unit could make that go away without running 24/7, which I would prefer not to do.

Sorry for the long wall of text. Any advice is greatly appreciated. Thanks!
Mr. Rumples
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Re: Sizing Window AC for Small Rooms

Post by Mr. Rumples »

I went through this just two weeks ago when my central AC was down due to a project. It was 95F out (in the shade) and humid; the sun was beating down on it. The little 5,000 BTU cooled not only the bedroom (about 150 sf), but also the adjacent bedroom with a fan on the floor blowing it out of the room where it was located. I'd say 5,000 is fine, 6,000 to be safe. The key is to be sure the wiring can handle the load so there shouldn't be any other big items pulling power on the circuit.

Too big of a unit in a bedroom and you will get too cold.

I grew up without AC and frankly prefer window units to central air...I am in the minority of course.

If your house has eaves, put them in a window with eaves to help divert the sun and protect from rain.
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dboeger1
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Re: Sizing Window AC for Small Rooms

Post by dboeger1 »

Mr. Rumples wrote: Mon Jul 19, 2021 5:40 pm I grew up without AC and frankly prefer window units to central air...I am in the minority of course.
Same here, I treasure simplicity and not having to tear up the house to retrofit something fancy.
Mr. Rumples wrote: Mon Jul 19, 2021 5:40 pm I went through this just two weeks ago when my central AC was down due to a project. It was 95F out and humid; the sun was beating down on it. The little 5,000 BTU cooled not only the bedroom, but also the adjacent bedroom with a fan on the floor blowing it out of the room where it was located. I'd say 5,000 is fine, 6,000 to be safe. The key is to be sure the wiring can handle the load so there shouldn't be any other big items pulling power on the circuit.
Thanks for the data point. My use case would likely be to treat each room as a separate zone, so it sounds like 5k BTU in each should be fine. I am concerned about the load with multiple units though. I should probably look into that.
Carousel
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Re: Sizing Window AC for Small Rooms

Post by Carousel »

dboeger1 wrote: Mon Jul 19, 2021 5:27 pm Both rooms are approximately 100 square feet, so quite small and well within the stated bounds for 5000 BTU window units.
Can't help with your questions, but do check the noise level of the AC unit. Some are loud enough to cause hearing loss over a long time. Here's a CR article:
https://www.consumerreports.org/hearing ... ring-loss/
You can buy a sound level meter for $50 or less. (That's what I used to check my bedroom AC unit.)
sport
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Re: Sizing Window AC for Small Rooms

Post by sport »

If an AC unit is too big, it will cool the space without removing enough humidity. You can end up with a cold damp room. My understanding is that bigger is not better. You want to use the proper size, not too small and not too large.
Big Dog
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Re: Sizing Window AC for Small Rooms

Post by Big Dog »

duplicate post
Last edited by Big Dog on Mon Jul 19, 2021 6:37 pm, edited 1 time in total.
Big Dog
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Re: Sizing Window AC for Small Rooms

Post by Big Dog »

the feds have a good article on sizing.

https://www.energystar.gov/products/hea ... oning_room

For a nursery, look for one that is quieter on the decibel scale. (not Frigidaire) Cheaper is gonna be louder/noisier.
Last edited by Big Dog on Mon Jul 19, 2021 6:40 pm, edited 2 times in total.
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RickBoglehead
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Re: Sizing Window AC for Small Rooms

Post by RickBoglehead »

Room air conditioners are noisy. Very noisy. Central air is far superior. Had a window and a room a/c in our cottage. Very loud.
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suemarkp
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Re: Sizing Window AC for Small Rooms

Post by suemarkp »

A typical floor vent puts out about 100 CFM of air flow. When cooling, that translates to 1/4 ton which is about 3000 BTU. If similar houses in your area have one HVAC register in a room that size, then 3000 to 4000 BTU is what you need. If they have two registers, you'd need 5000 to 8000 BTU. So I think the 5000 BTU will be plenty.

You don't want to oversize. Also, a larger unit needs more power. Many bedrooms share a single 15A electrical circuit. So a small window AC in two separate room on the same circuit are going to use a lot of the available power, but there should still be some left over. If you put in a huge one, you'll blow the breaker when you use any other significant electricity.
Mark | Somewhere in WA State
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dboeger1
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Re: Sizing Window AC for Small Rooms

Post by dboeger1 »

Carousel wrote: Mon Jul 19, 2021 6:28 pm Can't help with your questions, but do check the noise level of the AC unit. Some are loud enough to cause hearing loss over a long time. Here's a CR article:
https://www.consumerreports.org/hearing ... ring-loss/
Very interesting, especially for a newborn baby. I'm not concerned with long term damage for adults or older kids just because they would likely not be used year round, only in the hotter Summer months and mostly just while someone is in those rooms, which may be mostly at night since our living room is like half the house and where most of the entertainment is set up. But for a nursery, I could see how it would be a bigger issue, given the baby will likely spend many hours sleeping there.
sport wrote: Mon Jul 19, 2021 6:35 pm If an AC unit is too big, it will cool the space without removing enough humidity. You can end up with a cold damp room. My understanding is that bigger is not better. You want to use the proper size, not too small and not too large.
Our area has very low humidity. Not only do we like to run humidifiers, but I was even considering supplementing these window units with one of those ice-based evaporative units. We wake up with dry mouths pretty much every night. That being said, I believe there are other efficiency-related concerns with regards to oversizing.
suemarkp wrote: Mon Jul 19, 2021 6:47 pm Also, a larger unit needs more power. Many bedrooms share a single 15A electrical circuit. So a small window AC in two separate room on the same circuit are going to use a lot of the available power, but there should still be some left over. If you put in a huge one, you'll blow the breaker when you use any other significant electricity.
That's what I'm afraid of. I suspect most units would work fine under normal usage, but I already know the way my wife is, she'll try to overload it when I'm not looking some day. I remember hen she discovered that she could not run a bunch of the kitchen appliances at the same time as the microwave. I wasn't going to splurge for Energy Star originally based on purchase price differences, but with random price fluctuations, it looks like they might be worth it, if for no other reason than they save a little over 1A each. I don't actually know how the house is wired, and we will eventually need to come up with a solution for the 3rd master bedroom (although that one's tricky because it's a very large glass sliding door as opposed to a standard window), so that could be 3.5A+ saved on a circuit if they're all together.
suemarkp wrote: Mon Jul 19, 2021 6:47 pm A typical floor vent puts out about 100 CFM of air flow. When cooling, that translates to 1/4 ton which is about 3000 BTU. If similar houses in your area have one HVAC register in a room that size, then 3000 to 4000 BTU is what you need. If they have two registers, you'd need 5000 to 8000 BTU. So I think the 5000 BTU will be plenty.
Very interesting. To be honest, I haven't been in enough houses around here to know how to apply that knowledge. The Bay Area's pretty experience so we're in about the smallest starter SFH available, and I don't know that our construction is directly comparable to most of the larger homes that would have AC, particularly with regards to insulation. I put some holes in walls when installing security cameras, and it looks like there's very little insulation. I suspect that's because there is very little actual exterior wall space when you subtract the windows, doors, garage, etc. The South-facing front of the home is ironically much cooler than the North-facing back where the bedrooms are, I think because of tree shade and the slope of the property. Anyway, all I'm saying is whatever better-built houses uses, I wouldn't be surprised if we need more due to lack of insulation the heat that seems to build up behind the house. I vaguely recall seeing homes with 1 floor register per room in the area, so 5k BTU is probably in the ballpark.
vasaver
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Re: Sizing Window AC for Small Rooms

Post by vasaver »

Think about investing in a mini-split.

We have pieced together Window ACs and if I were you I would seriously consider doing a mini split system and get each room to the temperature you want it.

Window ACs are usually noisy, bugs can crawl in and your wiring might not be able to handle the load in an older house.

If you can swing it get a few quotes enjoy your lives.

https://www.nytimes.com/wirecutter/revi ... nditioner/

Costco has some good ones as well (precharged for amateur installation) that are a good price.
https://www.costco.com/mrcool-diy-18k-b ... 73104.html
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Padlin
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Re: Sizing Window AC for Small Rooms

Post by Padlin »

I've never had bugs come in thru an air conditioner, around them maybe, if not well sealed, but that's just me.

A single evaporator mini split cost me about $4k to have installed. The op would be looking at a 3 evaporator unit for the bedrooms unless they leave all the doors open, and a single for the rest of the house. That's going to be pretty big bucks compared to window units.

Could put in something like 6 or 8k window units, and have an electrician put in dedicated circuits if you start popping breakers. Way cheaper then mini's. When I heard of Mini's, I had one put in the family room, I can hear the TV without it being on max volume.

I've found cheap window units are very noisy, I've had a couple Friedrich units and had good luck with them, they run around $400 for the smaller ones.

No idea about horizontal units though.
Regards | Bob
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dboeger1
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Re: Sizing Window AC for Small Rooms

Post by dboeger1 »

vasaver wrote: Mon Jul 19, 2021 7:56 pm Think about investing in a mini-split.
My original plan was to get a multi-zone mini-split, but that seems complicated by the structure of the house. It would work in the 2 smaller bedrooms I mentioned, but ironically, the larger master bedroom is the problem because it has a large sliding glass door, which likely doesn't leave enough room for the typical head unit, if it's even allowed to install it in the header over the door, which I honestly don't know. There is not enough room on either side of the door to fit it. I know there are ceiling units available for such systems, but my understanding is they require a certain amount of overhead clearance for ductwork to the exterior, and that bedroom is under the flat portion of the roof with no attic space above it. The room is also adjacent to the neighbors (it's what's called an "attached single-family home" here), so literally the only way I can think of to get the head unit in here is to put it on the interior wall and have the conduit go out the side of the unit through a small hole in the back exterior wall. I don't actually know if this is even supported; I was under the impression that those head units were only designed to go directly up against the exterior wall and have the conduit poking out the back.

Then there's the complication of the kitchen and living room, which are by far the largest rooms in the house, but are currently the coolest and most tolerable. As I explained in an earlier comment above, there's really no proper way to run any kind of duct work or piping from the back of the house to the front, so the only way I can think to get a zone in the living room is to run the conduit all the way around the side of the house. It may be doable, I'm not sure. Otherwise, the living room would need its own separate system with compressor in the front. And then the kitchen, which is along the back of the house, has similar issues to the master bedroom in that most of the exterior wall is taken up by a sliding glass door.

To be honest, I'm not much of a handyman around the house. There are projects I will do myself, but I'm liable to screw up the part with bending the conduit or charging the systems that are not pre-charged. This seems complicated enough that I'd probably have to hire a professional, and I don't doubt that I would get up-charged due to the structure of the house. It's a small house, but there's just no easy, convenient way to run anything from front to back. I ran into a lot of these same issues when installing security cameras myself, and ended up just running the wires along the ceiling inside the house, which looks silly but gets the job done. Not only would window units avoid anything destructive, but it should be relatively simple to remove them in the colder months and replace them whenever they eventually die.

Another issue, as I've alluded to in previous comments, is that the house seems barely insulated. The only wall I've actually seen with insulation is the wall between the living room and garage. I'm assuming the garage walls are all insulated, and maybe the side alley wall, but the rest seemingly don't have any insulation, probably because they're mostly glass doors, windows, and structural headers. I suspect even quality insulation would do very little for those walls because of all the glass and wooden beams. That's probably why AC was never installed before. I was honestly kind of surprised when this house didn't come with AC because the previous owner renovated the interior quite nicely before selling, but I kind of understand now.

Anyway, I should probably get a quote for professional installation of a mini-split just to see what they say, but I would be shocked if it wasn't several thousand more. And again, we only really have a few unbearable weeks/months of the year here. I could see it being $10k+, compared to maybe $1k when all is said and done with the window units where they're most needed. I suppose some of that extra cost might be made up in home equity, but that's a bit of a long-term gamble.
andypanda
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Re: Sizing Window AC for Small Rooms

Post by andypanda »

Also consider your ceiling height. My 19`6 house had 10-foot ceilings. The square footage suggestion on the AC box didn't apply.
Also consider your wall insulation. My old house had 14-inch solid brick exterior walls with an inch of plaster on the inside and no insulation.
And so forth. Are your windows leaky? Are there large gaps under or around the room doors to let the cold air escape into the hall?
vasaver
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Re: Sizing Window AC for Small Rooms

Post by vasaver »

dboeger1 wrote: Mon Jul 19, 2021 9:03 pm
vasaver wrote: Mon Jul 19, 2021 7:56 pm Think about investing in a mini-split.
My original plan was to get a multi-zone mini-split, but that seems complicated by the structure of the house.
A few more options to consider - since we have many of the same issues you have.

Window Minisplit Soleus saddle (prices are highest right now off season). We have a 8k wifi one and it super quiet and low wattage.
https://www.amazon.com/Soleus-Air-Exclu ... 2231872245

Forestair portable minisplit - Costco in the US carries these at different times of the year.
https://www.youtube.com/watch?v=BrlESvS2QjU&t=3s
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tyrion
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Re: Sizing Window AC for Small Rooms

Post by tyrion »

Long term, you're going to want a mini-split. It will be quiet, efficient (for air conditioning, at least), and effective.

We faced a similar quandary 15 years ago. Installed a sleeve in our living room wall and put a 12k BTU 'though-the wall' air conditioner in it. It ran like a champ and we used a fan inside the house to spread the cool air around. Later it was supplemented with a 5k window unit in the master bedroom and more fans. It made the hot days tolerable but that's about it. 15 years ago mini splits were more of a new solution. But I wish we would have just put in a 4 zone mini-split. One for each bedroom and a bigger one for the main open living area.

So for you? Definitely spend a few thousand dollars to get something good. Let the techs figure out how to mount the thing in your bedroom. The world is only getting warmer, Bay Area included.

If you want to buy a cheap window unit for the summer, that's not a bad idea. Then put in a more robust solution when pricing is more favorable.
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Re: Sizing Window AC for Small Rooms

Post by LilyFleur »

dboeger1 wrote: Mon Jul 19, 2021 9:03 pm
vasaver wrote: Mon Jul 19, 2021 7:56 pm Think about investing in a mini-split.
My original plan was to get a multi-zone mini-split, but that seems complicated by the structure of the house. It would work in the 2 smaller bedrooms I mentioned, but ironically, the larger master bedroom is the problem because it has a large sliding glass door, which likely doesn't leave enough room for the typical head unit, if it's even allowed to install it in the header over the door, which I honestly don't know. There is not enough room on either side of the door to fit it. I know there are ceiling units available for such systems, but my understanding is they require a certain amount of overhead clearance for ductwork to the exterior, and that bedroom is under the flat portion of the roof with no attic space above it. The room is also adjacent to the neighbors (it's what's called an "attached single-family home" here), so literally the only way I can think of to get the head unit in here is to put it on the interior wall and have the conduit go out the side of the unit through a small hole in the back exterior wall. I don't actually know if this is even supported; I was under the impression that those head units were only designed to go directly up against the exterior wall and have the conduit poking out the back.

Then there's the complication of the kitchen and living room, which are by far the largest rooms in the house, but are currently the coolest and most tolerable. As I explained in an earlier comment above, there's really no proper way to run any kind of duct work or piping from the back of the house to the front, so the only way I can think to get a zone in the living room is to run the conduit all the way around the side of the house. It may be doable, I'm not sure. Otherwise, the living room would need its own separate system with compressor in the front. And then the kitchen, which is along the back of the house, has similar issues to the master bedroom in that most of the exterior wall is taken up by a sliding glass door.

To be honest, I'm not much of a handyman around the house. There are projects I will do myself, but I'm liable to screw up the part with bending the conduit or charging the systems that are not pre-charged. This seems complicated enough that I'd probably have to hire a professional, and I don't doubt that I would get up-charged due to the structure of the house. It's a small house, but there's just no easy, convenient way to run anything from front to back. I ran into a lot of these same issues when installing security cameras myself, and ended up just running the wires along the ceiling inside the house, which looks silly but gets the job done. Not only would window units avoid anything destructive, but it should be relatively simple to remove them in the colder months and replace them whenever they eventually die.

Another issue, as I've alluded to in previous comments, is that the house seems barely insulated. The only wall I've actually seen with insulation is the wall between the living room and garage. I'm assuming the garage walls are all insulated, and maybe the side alley wall, but the rest seemingly don't have any insulation, probably because they're mostly glass doors, windows, and structural headers. I suspect even quality insulation would do very little for those walls because of all the glass and wooden beams. That's probably why AC was never installed before. I was honestly kind of surprised when this house didn't come with AC because the previous owner renovated the interior quite nicely before selling, but I kind of understand now.

Anyway, I should probably get a quote for professional installation of a mini-split just to see what they say, but I would be shocked if it wasn't several thousand more. And again, we only really have a few unbearable weeks/months of the year here. I could see it being $10k+, compared to maybe $1k when all is said and done with the window units where they're most needed. I suppose some of that extra cost might be made up in home equity, but that's a bit of a long-term gamble.
I love my mini-splits. The one in the living room and the one in the master bedroom both are between top of the sliding patio doors and the ceiling. They are quiet (MUCH more quiet than window units, both inside and out) and are energy efficient. The ductless system was perfect for my home. I did have to get a bigger electrical panel, and there were holes in the ceilings for the wiring, but I live in a ground-floor condo so they couldn't go through an attic. I rarely use the unit in my spare bedroom; I keep the door shut most of the time. Where I live, humidity is much more of an issue, and for most of the summer so far, in my living/kitchen/dining area, I have just been running the dehumidifier function rather than the AC.

Are your patio doors original? When I replaced my single-glass, original 1978 patio doors with double-glass patio doors and windows, it helped insulate my home a lot--in my living/dining/kitchen area, almost one entire wall is patio doors and windows.

My mini-splits also provide heat in the winter, so it eliminates furnace replacement, which is expensive. My heater never worked, so I removed it completely and gained an extra closet.
Katietsu
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Re: Sizing Window AC for Small Rooms

Post by Katietsu »

As a temporary move, $15 worth of foam and weatherstripping and your portable unit should be more than up to the task. I think you are spending too much energy trying to cool the great outdoors. Add $5 for a temporary light blocking blind to keep the sun from coming in and you will buy yourself time for a more permanent solution.
bacon4retirement
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Re: Sizing Window AC for Small Rooms

Post by bacon4retirement »

If your portable AC is a single hose design, keep in mind that it the actual cooling is only about half of the adversided BTU rating. The testing standard for single hose units ignores that single hose AC units draw in hot air from the outside, than then the hot outside air also has to be cooled.

Other lower energy intensive changes such as adding insulation, sealing gaps, adding shade, and putting in an attic fan can dramatically reduce the size of AC unit you might need.
Mr. Rumples
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Re: Sizing Window AC for Small Rooms

Post by Mr. Rumples »

Yes, the noise was reason why I had the AC in one bedroom, but I slept in the other. This might be even more critical for children who are exposed to all sorts of loud noises. Having an AC running in the same room as sleeping might mean they get no quiet. I did see at Lowe's some of the window units have decibel ratings on them.

Regarding doors and light / heat reflection. When in CO I had the privilege to attend an event at the Governor's Mansion. The rear has a sunroom which faces south, getting the full force of the CO summer sun. When I asked, I found that they hired a company to install on the inside some sort of clear reflector plastic to the window. I hired the same company and it helped with our windows. I think it was around $300 for both sliding balcony doors but that was about 10 years ago. Rear of the CO Governor's Mansion (Boettcher Mansion):

https://jasonstravelsdotcom.files.wordp ... ansion.jpg
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telemark
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Re: Sizing Window AC for Small Rooms

Post by telemark »

If you get a window unit with an inverter and a variable speed compressor, instead of cycling on and off the compressor will run slower after the desired temperature is reached. Which should alleviate the problems associated with sizing too big. The Wirecutter likes this one, and LG and Frigidaire also make inverter models.

Disclaimer: I don't own an inverter AC.
talzara
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Re: Sizing Window AC for Small Rooms

Post by talzara »

dboeger1 wrote: Mon Jul 19, 2021 5:27 pm We actually have a portable unit ... It's a 10k BTU LG unit. From my research online, it looks like it's 6500 BTU equivalent by DOE standard, and it struggles but does barely cool the room sufficiently while running continuously, but with one critical flaw, which is that the stupid flat piece that goes next to the sliding window isn't long enough for our window, so there's a small uncovered square opening in the top corner of the window. ... It has me worried that 5k BTU is not enough, but again, that might just be the poor setup we have now.
A 5,000 BTU/h window air conditioner should have about twice the cooling capacity of your "10,000 BTU/h" single-hose portable air conditioner at 100°F.

Portable air conditioners depressurize the room, so they draw in hot air from outside. The portable air conditioner is blowing 55°F air from the evaporator, but since you have a hole in your window, it's also drawing in 100°F air from outside. You'd be lucky to get 2,000 BTU/h of net cooling at that temperature.

Window air conditioners do not depressurize the room. They can typically deliver at least 70% of their rated cooling capacity at 100°F, and some of them can deliver 100% because the manufacturer understates their capacity. You can expect 3,500 BTU/h from a 5,000 BTU/h window air conditioner.
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dboeger1
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Re: Sizing Window AC for Small Rooms

Post by dboeger1 »

I appreciate all the input, but just to clarify, I'm aware of the shortcomings of portable units, haha. I keep getting responses about how portables are not good, and believe me, I'm there, lol. I know our current uninsulated setup is a joke, but it was mostly just because we had a free unit to try and see how it handled the room.

I was about to pull the trigger on some window units that are on sale, but when I spoke to the wife, she insisted she wanted to go with a proper mini split installation. Of course, she wants to have her cake and eat it too, so she's under the impression we can get a DIY unit and either do the installation ourselves or hire an unlicensed friend to do it for $500. That's a pipe dream given the structure of the house. If nothing else, I want a proper electrician to do the electrical work, because the breaker box is in the front of the house, the majority of the units will be in the back, and as I said, there are no clear ways to run things from front to back without running external cabling and conduit along the side of the house. I'm inclined to just hire a proper outfit to do the job right just to get it nice and comfortable before the baby arrives, and then we would have heat pump functionality to supplement our gas furnaces which are more in the middle of the house and don't heat the bedrooms well. I expect it to run a good $6k-$10k, maybe even more, but we'll see what they quote us.
talzara
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Re: Sizing Window AC for Small Rooms

Post by talzara »

dboeger1 wrote: Tue Jul 20, 2021 1:09 pm I appreciate all the input, but just to clarify, I'm aware of the shortcomings of portable units, haha. I keep getting responses about how portables are not good, and believe me, I'm there, lol. I know our current uninsulated setup is a joke, but it was mostly just because we had a free unit to try and see how it handled the room.
You said you didn't think 5,000 BTU/h would be enough because a "10,000 BTU/h" single-hose portable barely works.

Someone else told you that a central air conditioner would only give you 3,000 BTU/h, so a 5,000 BTU/h would be plenty. However, you objected that your house was not as well-built as other houses.

I'm telling you that a 5,000 BTU/h window air conditioner will deliver twice as much cooling as your portable air conditioner. You said that your portable "struggles but does barely cool the room sufficiently." Since you're already running your portable in the same room, this removes construction quality as a variable.
talzara
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Re: Sizing Window AC for Small Rooms

Post by talzara »

bacon4retirement wrote: Tue Jul 20, 2021 1:45 am If your portable AC is a single hose design, keep in mind that it the actual cooling is only about half of the adversided BTU rating. The testing standard for single hose units ignores that single hose AC units draw in hot air from the outside, than then the hot outside air also has to be cooled.
The DOE rating includes the effect of air infiltration. That's why the OP's "10,000 BTU/h" portable air conditioner has a DOE rating of only 6,400 BTU/h. However, even that number is much too high.

Due to industry lobbying, the DOE single-hose test is done at an interior temperature of 80°F and an exterior temperature of 80°F. The DOE wanted the test to be done at an exterior temperature of 95°F, but the industry didn't want their "10,000 BTU/h" air conditioners to be rated at 2,000 BTU/h.
Carousel
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Re: Sizing Window AC for Small Rooms

Post by Carousel »

dboeger1 wrote: Mon Jul 19, 2021 7:37 pm
Carousel wrote: Mon Jul 19, 2021 6:28 pm Can't help with your questions, but do check the noise level of the AC unit. Some are loud enough to cause hearing loss over a long time. Here's a CR article:
https://www.consumerreports.org/hearing ... ring-loss/
Very interesting, especially for a newborn baby. I'm not concerned with long term damage for adults or older kids just because they would likely not be used year round, only in the hotter Summer months and mostly just while someone is in those rooms, which may be mostly at night since our living room is like half the house and where most of the entertainment is set up. But for a nursery, I could see how it would be a bigger issue, given the baby will likely spend many hours sleeping there.
Yes, babies need special care!
***
In 2014, the American Academy of Pediatrics (AAP) tested 14 white noise machines designed for infants. They found that all of them exceeded recommended noise limits, which is set at 50 decibels.

In addition to increased hearing problems, the study found that using white noise increased the risk of problems with language and speech development.

Based on the findings of the AAP, pediatricians recommend that any white noise machines should be placed at least 7 feet away (200 cm) from your baby’s crib. You should also keep the volume on the machine below the maximum volume setting.
***
Topic Author
dboeger1
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Re: Sizing Window AC for Small Rooms

Post by dboeger1 »

I realize the original discussion of this thread has more or less run its course, but I figured I'd give an update on our first quote for anyone curious or going through something similar. Around $40k for a 5-zone mini-split installation, which absolutely blew our minds. To be fair, this was a very experienced, professional installer, and the installation they proposed was quite a bit fancier and more discreet than what I expected. They want to put the condenser on the flat part of the roof and spider out the line sets from there, running them through the top of the internal walls so that no lines appear along the exterior sides or the inside of the home. In addition to all the obvious work that entails, they would need a crane to lift all the equipment onto the roof, which I was not expecting. I give them props for ambition, and it's certainly an interesting all-out option, but that is quite a bit higher cost than I was expecting.

My wife is in the process of getting some other quotes over the next few days, and it sounds like there are some handyman types willing to do the work un-permitted for under $20k, probably with the condenser and exposed line sets in the back yard and only 3 zones for the bedrooms though. This is a project I'd rather pay extra to do by the books, I just don't know if $40k is the kind of extra we should be talking about, when $1k in window units would do the trick. But then they're window units. Sigh.
talzara
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Re: Sizing Window AC for Small Rooms

Post by talzara »

dboeger1 wrote: Wed Jul 21, 2021 6:49 pm I realize the original discussion of this thread has more or less run its course, but I figured I'd give an update on our first quote for anyone curious or going through something similar. Around $40k for a 5-zone mini-split installation, which absolutely blew our minds.
If ductless mini-splits are too expensive, another option would be a high-velocity mini-duct system. The mini-ducts are only 2" in diameter, so they'll fit in the ceiling under the flat roof.

Spacepak and Unico are the two big high-velocity brands.
Topic Author
dboeger1
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Re: Sizing Window AC for Small Rooms

Post by dboeger1 »

We got another quote today for a more normal installation for between $11k-$13k depending on zones. Of course, it doesn't really compare to the original because the compressor would be in the back patio area and the line sets would run quite some distance along the exterior sides of the house, but the price is more in line with what I expected, albeit still a bit higher. I wouldn't be surprised if there was a post-pandemic bump included in there, as that seems to be going on a lot lately. We unfortunately got bit by a sudden $700 price increase on garage door replacement between the time of our quote and the time we were ready to schedule the work. The joys of home ownership. Maybe I'll just use mental accounting and consider these projects my bond allocation. The ROI is probably about the same these days.
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