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Comment by nimbius | Hacker News Reader

Anecdotal evidence but my ex boyfriend was an HVAC technician and frequently serviced suburban households. He was always stunned at how cold most customers wanted their homes in the summer. "theyre like chubby little eskimos in front of the TV" he used to chuckle, and most would ardently refuse energy saving ideas like acclimating to 75 degrees in the home, installing ceiling fans, or opening windows instead of running the HVAC system. Most people would just run the system constantly until the blower died or the compressor burned up every six or seven years.

Summertime is supposed to get a little warm :).

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There’s a possible explanation: humidity. The temperature that people find comfortable depends on humidity, and most AC systems have little or no ability to independently control temperature and humidity. Designing a system to achieve, say, 75F at 50% RH in a given climate for most of the summer is a black art, and most systems fail. So you can get 75F and feel sticky or you can get 65F and feel okay if slightly chilly.

A lot of builders in humid climates will install AC and central dehumidification, which can work better. In theory, one can tweak the indoor heat exchanger temperature to change the sensible vs latent cooling ratio, and there is at least one obscure heat pump vendor that claims to do this on the fly. I don’t know how well it works in practice.

For most houses in the south, if your having humidity problems in the 75F range your system is to large. AKA, flipping the AC on, and blasting a lot of air with a 35F drop into the house, then cycling off for 70% of the time doesn't remove nearly as much humidity as just running a smaller system closer to 100% of the time. Further most homes not built in the past 15 years are hugely flow constrained and mis balanced. So the AC runs, but doesn't provide even airflow so there are hot/cold spots.

For areas where its not 90+ out for 8+ months a year, a large part of the comfort of the newer systems (and their larger SEER ratings) is that they can run at 1/2 speed (or whatever) to keep the AC unit running longer. Plus they are frequently sold with duct work upgrades.

This is also why a "properly sized" system with a high EER can frequently save money over a high SEER system with a lower EER in FL/TX/LA/MS/etc.

The problem though is that pretty much 100% of AC companies are just going to put in the same size system as they took out, and the home builders are just seat of the pants overspecing everything. It should be possible to determine heat load, and TXV flow/etc over a year, and then come back and resize the condenser/evaporator/airflow to go just slightly over the worse case. But no one is going to do that, and if they mess up and the customer can't keep the house at 78F when its 110 out, its going to be a costly problem to fix. So, better to just overbuild everything and deal with the significant efficiency decrease.

> He was always stunned at how cold most customers wanted their homes in the summer. "theyre like chubby little eskimos in front of the TV" he used to chuckle, and most would ardently refuse energy saving ideas like acclimating to 75 degrees in the home

Or maybe they like cooler temperatures. Kind of like how sometimes you see someone outside wearing a tshirt + shorts when the weather's only 50-60f. It's only absurd if they've set the temperature low AND they're shivering or wearing a jacket/sweater/blanket.

I wonder if there's a correlation between population BMI and a propensity to wear non-insulating clothing. Of course the natural correlation would be body fat % but I wonder if it shows up in large population metrics like BMI. Certainly with a 40% obesity rate, we could see a large number of people claiming they 'run hot' when they're really just obese.

Air conditioning probably makes some people slightly fatter. There is a metabolic cost to regulating body temperature. As the temperature rises you actually burn more calories on thermoregulation.

https://abcnews.go.com/Health/Diet/story?id=2120381&page=1

Thank you for sharing that. It's an interesting claim but sadly it doesn't say what the name of the report was. It sounds a bit odd to me, though. Surely you cool down by expending less energy, unless you spend that energy to actively respire to expel heat like dogs do.

I can't imagine there are many people panting in their warm houses though.

Yes it takes energy to actively reject heat. From a thermodynamic standpoint, cooling isn't free.

I would like to politely disagree; I think the point of having control of the temperature in your house is to have it be exactly the way you want it all the time. Now, it may take a while for the technology to catch up to that, but I think people would happily install a new system every few years, rather than lose that control. I personally like it cool enough to wear layers, regardless of what month it is.

The issue is that many people do not realize the range to which they can acclimatize. And the acclimatization has varying degrees of value depending on the temperature differential to outdoors.

Eg: in Canada one can keep their home a few degrees cooler in the winter to save quite a bit of money. Same idea in hotter climates -- keeping it 75 instead of 70 is something one can acclimatize to, but has more value when the out door temperature is 100f vs 80f.

Overall I think it's just momentum. When I had a nest I used the dynamic range that said only cool if my place is over 78 and only heat if it's 68. Everything else, just roll with the ambient.

> The issue is that many people do not realize the range to which they can acclimatize.

Said acclimatization normally comes with downsides... When its hot, one might be less productive, feel less motivated to get stuff done, etc. It's pretty hard to measure that cost on a personal basis.

If you feel worse enough to be less productive, have you actually acclimatized?

I grew up in a house with air conditioning on all the time during the summer and thought that there was no way I could ever handle indoor temperatures of, say, 75. Then I spent a couple years in Arizona and wanted to save on AC costs in the summer, it took a while to get used to, but now an indoor temperature of 70 in the summer feels very cold to me.

As a kid in Phoenix my parents forbid setting the thermostat below 80, unless the humidity outside was low enough we could use the swamp cooler instead of the air conditioner.

Now I'm comfortable at 78 with a ceiling fan, to me 75 is cold and 70 would be freezing

Nahh, I just run hot. I've lived in a shared place where I don't control the thermostat and the person who does was loathe to let it go above 77 degrees. After months on end, I'd still get uncomfortably warm in such a temperature. On the other hand, I can sit comfortably in 55 degrees in short sleeves with wind. I also have very low body fat, so that's not the culprit either. Believe it or not, people have different preferences and optimal temperatures. I just wish everyone would err far to the side of cold: you can always put on a jacket; I can't keep taking clothing off.

But what is the point of cooling your apartment to 65 Fahrenheit, when there's 90 degrees outside? In summer you would still wear shorts and t-shirt when inside, not sweatpants and hoodie, right? Setting AC to 75 degrees instead would be much more reasonable.

I wear shorts and t-shirt in sub-50 degree weather. 75 degrees is uncomfortable, even if I'm sitting doing nothing. Forget about doing things around the house at that temperature. At a certain point, I'd rather not even have AC at all than spend money to make it marginally more comfortable. (I also have huskies who don't like 75 degrees all that much.) On the flip side, I'm more than comfortable having the house be 55 degrees in the winter.

This is why it makes no sense to question how cold or warm other people like their home. I'm probably most comfortable around 25 degrees C (except perhaps when I'm exercising) - this is both during the summer and during the winter (and also during the day and night).

One difference, and part of the appeal, is how quickly you cool off after being outside for a long time.

Let's say it's 100°F, and you're outdoors for 2 hours. You feel lethargic and sapped of energy, and you look forward to going inside. When you finally do, you get a gigantic cold beverage, take off your shoes, plop down on the couch, and wait to feel normal again. It might take 30 minutes before you start to get there.

If it's 65°F inside, this process happens faster than if it's 75°F.

No doubt, the moment you get inside, you already feel better whether it's 65°F or 75°F because neither one is 100°F. But if you're alternating between inside and outside a lot, colder is still preferable.

Actually I find that if I'm acclimated to 90-degree temperatures it doesn't take very long for me to cool down in 75-degree temperatures at all. That's how acclimatization works, after all. You get used to the temperature and your body doesn't perceive it as hot or cold anymore.

Given the amount of environmental damage that energy production causes, expending huge amounts of energy to keep a large volume of space at a precise temperature rather than being a little flexible in how you dress seems pretty selfish to me. (If there was an appropriate Pigovian tax in place then I'd say fair enough, it's your money).

I wish the boss would accept that, workplace dress code means blasting the A/C all summer.

Meanwhile in NYC: my apartment is regularly heated to 85 degrees in the winter, and it's commonplace to open the window and let in some freezing air to fight the radiator.

This is apparently an artifact of the 1918 flu pandemic: building architects / heating engineers intended for windows to be kept open to ventilate spaces in the winter, and so steam heating systems were over-provisioned. A number of friends in old apartments in Pittsburgh had the same issue with building heat.

(Relatedly, I wonder what effect the current pandemic will have on the modern trend of well-sealed homes...)

Huh, I always assumed it was due to minimum temp laws, where it was cheaper to just heat everything full blast and never have to worry about a 1st floor or basement apartment not getting enough heat, and cheaper than installing valves or thermostats in every unit.

Every apartment I've lived in around NY and North NJ was like this. All had steam radiator heaters, and the heating was so hot, especially in the fall and spring, that you controlled the temp by opening or closing the window over the radiator. All but one also had single pipe radiators[0], so you couldn't turn them down with the valve or you'd end up filling the radiator with water and breaking the system.

However parts of NYC do still have steam heating powered by a central plant (mostly ConEd iirc) so in the end it might actually end up more efficient with the windows open than having a per unit heater.

Edit: Wikipedia link on NYC's system https://en.wikipedia.org/wiki/New_York_City_steam_system

I guess it's just Manhattan that has central steam, but it also provides cooling via absorption chillers and steam for disinfection. Also much of this steam is basically a waste product of electricity generation, so the actual efficiency may be even higher.

Edit 2: I also found and article in NY Times that supports the spanish flu as the reason for this, and also describes 1 vs 2 pipe systems.

[0] https://www.nytimes.com/2016/03/13/realestate/radiators-stea...

Overprovisioning to ensure demand is met in the worst case also sounds like a very early-20th-century sort of design decision; that could be part of it!

Here's an interesting article about Spanish flu and radiators: https://www.bloomberg.com/news/articles/2014-02-17/our-indis...

"engineering manuals from the 1920s dictated that radiators and boilers be manufactured large enough for 'the coldest day of the year, with the wind blowing, and the windows open.'" (!)

>Overprovisioning to ensure demand is met in the worst case also sounds like a very early-20th-century sort of design decision

We're building 600 hp electric cars these days.

My parents live in England and visited the US. They are used to wearing jumpers in the house in winter. But they reported that the houses were always "freezing" inside despite being warm outside. Similarly, my girlfriend, who grew up in the US says she doesn't like air conditioning because it's "too cold". I don't understand this. You are supposed to use it to be comfortable, not cold.

I moved to a new apartment and noticed my roommates would turn the main floor into a freezer (I live on second floor). I noticed thermostat levels as low as 50 F.

A few days later the HVAC stopped working and what do we know, it's because of of ice buildup.

The other thing, the vent-ways are designed so my room on second floor has a floor-vent. This works for heating but not for cooling. The cool air that comes out of the vent stays in the region between the floor level and roughly 1 foot above it. So my feet are fine, but I'm otherwise feeling hot.

It's a straightforward solution that cooling-vent should be in the ceiling and heating vent on the floor. But it costs more to have this kind of installation that's why most landlords/home-owners don't go for it? I don't know.

A fan blowing the cool air up (or a ceiling fan running “backwards”) is the solution to that problem and a lot cheaper than running extra ductwork and controls to divert air inside the walls.

Sounds like it might be low on coolant, you might want to get it serviced.

Funnily enough, my thermostat had some bug last night and kept the air conditioner on all night long. It's usually set to 72F and it got down to 58F(while outside hit a low of 60). I got it to turn off, but since it's relatively cool and partly cloudy today, my house has taken all day to get to 66 and now I'm acclimatizing to it.

wow, you're lucky your a/c didn't freeze up

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