MAK, I lived in a barn conversion that seemed to me, at first, to be 'upside down'. The bedrooms and bathroom were on the bottom layer, partially earth shielded as the barns were on/in a hillside, the main living and kitchen area was the middle layer and the sitting room, office etc were on the top floor. When we were buying the place we thought long and hard about how to get a bathroom upstairs so we could put the main bedroom on the top floor. It wasn't straightforward so we moved in as it was.
After living there 12 months no way would I have changed things. The bottom-floor bedrooms were less cold in winter, being so sheltered, and beautifully cool in summer when the top floor would have you removing a layer of clothing.
Before I found myself buying a farm up here, I had longed to find somewhere I could live the old way - animals below, generating heat to warm the human habitation above. I still think it's a good idea. You wouldn't need a calving cam - just a peephole in the bedroom floor!

We have a number of tricks to keep ourselves warm - the main one is using work to heat us; if you're in the house long enough to be getting cold, the best thing is to get off your backside and do some work, that'll soon warm you up!

And when you come back in, the house feels warm as the air is warmer than outdoors, so you stay warm for long enough to have a meal, a hot drink and a wee rest - then it's time to do some more work. Woodburner on in the evening for a relax.
No2 trick is always put on warm dry clothes. We take the chill off pyjamas before going to bed (with hot water bottle in my case - BH likes an electric blanket, I don't); the clothes for morning are on the hot water tank; there's a little oil-filled electric rad we can use to dry outerwear, gloves, hats, wellies if there's no other available heat. We wear plenty of clothes, in layers is best, and you really can't beat wool. I've just made us both a pair of woolly slippers and the difference it makes to your whole body temperature is quite amazing.
As colliewoman says, get anything wet off as soon as possible and change for warmed dry.
As to food in the old days - well, I'm just about to wrap and hang a side of bacon to see how that compares to keeping it in packs of sliced in the freezer; root veg would be clamped; spuds and apples stored, then there's bottling / pickling (eggs, cabbage, beetroot, onions to name four obvious ones), cheese; grains can be stored. And I guess there'd always be fat you could use in place of butter (I used to love dripping on bread as a kid

) - and when you're working hard in challenging conditions, you can use a higher-fat diet without risk, I think. And I suppose you'd have a few animals that you could slaughter as the winter progressed, provided you had hay or other feed to keep them going as long as you needed.
You don't need a fridge in winter if you've a larder or cold room. At Tinkers' Bubble, the Jerseys were fed a little grain and kept milking through the winter, though at a reduced rate. The buckets were stored in a fast-running stream - every bit as good as a fridge

Milk for the 'house' was fetched by the jugful as required. When sufficient spare milk had collected, a batch of cheese would be made.