I teach, so I rarely sit down. The temperature in my room goes up and down like a yo-yo as classes come and go, but never above about 18 degrees in winter (as read by classroom thermometer).
I wear layers (including a slip or a cami). Kids wear layers too - school shirt, jumper, blaser, coat, hats and gloves. The layers come on and off through the day.
When they’re in their shirt sleeves complaining they’re cold, I suggest first of all jumper (they don’t seem to realise that yes, this will be warmer than just a blaser) then an additional ‘base layer’ (or ‘skin’ as they call them) under the shirt. They quite like that as the sporty ones have them for outdoor games anyway. Or a cami for girls. I never say ‘vest’ though. They don’t like that and would think I’m a crazy old lady 😜 , which to be fair is an image I like to cultivate.
I might take the same approach with a naïve colleague, who inappropriately dressed, complains of the cold. Keep it light hearted though. She actually might not really have a clue how to dress.
We are in the middle of a climate crisis and fuel prices are through the roof. We live in the Northern hemisphere. I don’t think it’s reasonable or practical to expect indoor premises to be heated to summer temperatures (e.g. 25) in mid winter. Likewise I despise air con fascists who insist on turning temp down to 16 in summer when were all in summer clothes (not that we have air con in school). They’re just as bad.
The Royal Society of Chemistry has room temperature as 20 degrees centigrade which is actually a nice comfortable temperature to most people. A pack of 3 camis costs £10 from Morrisons.