I suspect it very much depends what you are used to - I probably think of 15C as "comfortable" and 25C inside would be sweltering. Having said that I'm in Scotland - the other day we had heavy rain and it was 8C which is weather we could get at any time of the year!

Maybe I'm being dense and saying the same thing as you, but it's more about the difference from outside to inside. In the mid Atlantic of the US, 22C can be pretty pleasant, but in the South turning it below 26C is a much more pleasant setting. Meanwhile, spend time in Southern China and you'll be laughed at for going below 30C, because it makes you nearly unable to go outside. If I feel like the humidity outside is going to condense on me when I take the dog out, I'm cooling my house too aggressively.

Similarly, I don't heat above 15C in the winter. That way, getting dressed to go outside is less complex than suiting up for a space walk.

I must admit that I don't know the difference in temperature from inside to outside - for half of the year (say May to October) we don't have heating on and we don't even have air conditioning (I don't know anyone who has air conditioning at home in Scotland).

The main difference I'd see between inside and outside is the lack of rain and wind in the former - temperature difference is secondary.

What closing do you use at 15C? After a few years in Norway I can be OK in a t-shirt at 18C. Anything below that still requires a jacket or sweater to stay comfortable.

Not OP, but here in Austria I wear t-shirts for most of the year. I even used to go out in just a shirt on warmer winter days with only light snowfall, but nowadays I really notice the cold when I do that. Everything above 10°C is very comfortable to me. Among my friends and relatives I am the exception of course. Most of them dress in more layers, some even in summer.

Quite happy in a t-shirt at 15C - especially if doing something other than sitting at a PC!

Funny. I'm Scottish and I would find 15c utterly baltic, especially when inside.

I suspect its because we used to live in a very old property that was very difficult to heat. So we got used to it!

Edit: I remember going to the halls at Uni for the first time and nearly dying of the heat - never lived anywhere that had central heating. Got used to and, of course, felt like I'd been exiled to Siberia when I went to my parents ramshackle large house for the Xmas break.

Wow. I think of 15C as "comfortable if I'm outside doing stuff and wearing long sleeves", but inside, it's "put the heat on (to 18C) and put on a sweater". 25C inside is what we set the air conditioning to in the summer at night so it's easier to go to sleep, but in the day, 26.5 is fine. This is in the southeastern US, and I've converted all temperatures from how I normally think of them in F.

Also, my workplace keeps inside air conditioning much cooler than I would, around 20C, which is uncomfortably cold when I'm dressed for the summer weather (ranges from 27C to 38C).

In my department at my university, professors and staff usually end up bringing a sweater and leaving it in the office so they have it in the summer. It gets kind of cold in the offices.

I've set my apartment to 26C. I find that without the humidity (since the AC deals with that too), 26C is actually not too bad for the summer.

After moving from Phoenix to the Seattle area, I've noticed the 'feels like' temperature is about 11C difference. 30C in Phoenix feels like 19C in Seattle.

Humidity and/or wind?

I've noticed temperatures in Scotland on mountains feeling much colder than lower temperatures in the Alps.

Largely humidity.

In Denver, I could run for an hour in direct sunlight with the temperature about 30 C. In Washington, DC, that would have been suicidal.

Yes, but DC is famous for its humidity, whereas Phoenix is known for its "dry heat."

In Germany ~70°F (19-20°C) is considered "room temperature".

75°F is too damn warm. My brain pretty much stops working around 77°F.

It seems to be common practice here in northern Bavaria to only cool offices to about 5 C below outside temp - so if it's 35 C (95 F) outside, only cooling to 30 (86 F).

Fortunately, wearing shorts to work on extremely hot (over 30 C) days is also more socially acceptable here.

It once was in NZ too even in formal environments - we called them "walk shorts" https://en.wikipedia.org/wiki/Walk_shorts - but they are now derided as an historic "fashion crime".

You acclimatize. I'm from chilly Sweden and used to start wearing T-shirts when it hit 18 C. Right now it's 27 C and I'm actually feeling a bit chilly (it was 29 C yesterday). Summers reach 36 C with high humidity.

I recall reading (no ref) that nazi experiments determined the optimal temperature for mental performance was 59F, which coincidentally is the average temperature of the earth.

Optimal for Caucasians maybe. In my office in the tropics, anything below 20C (68F) will generate howls of protest.

I went to school in Northern Wisconsin, and we had a bunch of people from the Caribbean living in my dorm freshman year. There was one thermostat that controlled steam delivery for each floor of the building, and then the radiators in each room did their own thing.

The people from the Caribbean would turn the heat up to 80 degrees all of the time. It got to the point where the thermostats were pulled off the wall in the middle of the night by to keep them from being turned up.

I think probably 3/4 of the building had their windows open all winter, even when it was -20 below outside, just to keep the temp livable. The thing is that it doesn't do much with steam heat, since those radiators can pump out more heat than you can possibly imagine.

The physical plant ended up putting the thermostat within a metal box that was grouted to the wall.

I can understand though. The first time it hits 40 degrees after the summer, I'm freezing, but if it hits 40 in January I'm walking around with shorts on. It was still kind of funny to listen to them describe what being really cold is like: "I'm on fire! Why do I feel like I'm on fire from being cold!"

I'm sure I sound equally hilarious when I'm somewhere hot though.

We're talking about nazi experiments. I'd assume that the "for Germans" part is implied.

"Caucasians" also seems the wrong abstraction here in either case. If you put a Swede or Brit and a Spaniard or Italian in the same room, they'll likely have different opinions the optimal temperature too, yet all of these are pointlessly grouped as "Caucasian" just because some people like to pretend it sounds less racist than simply saying "white" (which is an equally useless category for most concerns).

I grew up in a pretty cool climate (Maine). Above 65 I begin sweating. Especially if the humidity is above 60%. 58 is ideal working weather as long as the humidity is low. 35-45 is ideal sleeping weather, with window cracked open so to allow a breeze to counter at the heat from the stove.

They may have the issue of only having one thermostat for the whole building. They then have to balance the demands of the people in the coldest part of the building and those in the warmest part of the building. If the system isn't well designed, those could be tricky to reconcile.

I would argue that if there isn't one thermostat per section or even per room, that the building is poorly designed.

> 75 - 78 F is perfect

Like hell it is. I sweat like a pig at 78.

Because you're not used to it. Which is part of the problem: change is hard.

We researched this and it seems like the 'optimal' temperature for office workers in warmer climates is 23-24 C or 73-75 F. In the winter your office temp should go down slightly to compensate for people wearing thicker clothes.

It depends on the climate. I used to live up north and we kept our houses and buildings around 68-71.

I live in a hot climate now and it's normal to keep inside temps 75-78.

In both places inside temps feel normal. The body seems to adjust it's idea of a comfortable temperature after acclimating to a new climate. When I first moved down south I kept my thermostat at 70 but it felt too cold after a few months. My most comfortable temperature is 76 now.

Even though I live in very warm/mild weather area, I ALWAYS try to keep a jacket handy if I know I will be going into an enclosed place to be sitting still, like theaters, restaurant, etc.

It's really silly that we have the technology of AC but cannot control the temperature accurately enough.

Yep, in the southeastern US it's routinely so cold inside that were it to get that cold in the winter, they would turn up the heat. Except that instead of wearing three layers of clothing you're in shorts and a T-shirt because it's 95F/35C+ and 100% humidity outside.

I don't think I'll ever get used to this. I don't see how it's possible even in principle to acclimate to such large swings in temperature over such a short time frame.

As a person from northeastern Europe living in Tokyo, I really hate the Japanese doing something similar -- in the summer they set their ACs to 20-22, when it's 35 outside, while in the winter everywhere inside is at 25+, quite often even as high as 28. Plus, their ACs are the 'blow freezing wind in the face' type, so it's extremely terrible for the health. I have taken to wearing a quilt+buff for the neck during the summer just to avoid getting sick all the time.

At least I sit next to a window, so I can let some warmer/cooler and fresher air to compensate, but it is such a waste of electricity, it drives me nuts.. It's also imposible to concentrate when the air gets too dry from the AC.

ends rant