In the UK we have plenty of old houses where there is no central heating, double glazing, loft insulation or fitted carpet. Typically the windows are wood framed 'sash' windows with the walls made from quite thick stone (1 - 4+ ft thick). Heating might be just the one fireplace with the kitchen cooker also there to warm the house up. I grew up in such a house and not once did I see mould.

Typically such houses were built centuries ago for 'cottage industries' such as making cloth. Back then family sizes were much larger so herds of children would also warm the place up. There might also be an actual herd of animals too - pets as well as livestock, e.g. goats.

Also changed is global warming - the pipes would freeze in the 1970's. Nowadays, nada.

There was an art to keeping warm. Most important - the fire. This would be open and powered by coal or wood. It would not be 'turned on' until the evening or early afternoon if it was the weekend (in winter). Once started the fire would suck air from wherever possible so that was the primary source of a draft. To mitigate the draft thick curtains would be the thing. The front door would have a curtain as would internal doors to the living room.

If you wanted to keep the fire 'in' for the next day you could smother the fire in coal and keep the ashes in underneath. Air would by restricted that way so the fire would slowly burn through the available fuel. Rake it through in the morning, top up with more coal and perhaps some kindling (a word I haven't used in a while) and the fire would live another day. The default would be 'off' though.

As for clothing, one word - layers. Wool rather than cotton or anything else. The layers approach also worked for the bed. If you were lucky you might have a hot water bottle, otherwise no heat in the bedrooms.

Due to the thick stone walls heat would be retained in winter and cold during summer. Consequently, regardless of the time of year, there would never be 'T-Shirt' weather indoors. You would be acclimatised to the cold and expect to see your breath in most of the house mid winter. There would also be that thing where the side of you facing the fire would be red hot whilst your back would be freezing. To solve this problem you would need the air to circulate, so no standing right in front of the fire, blocking the heat, even if that was very pleasurable to do.

A cast iron fire grate would be red hot and in your living room. Today's central heating does not do 'red hot' in the living room - radiators don't glow bright red like that although electric 'bar' fires get close.

As for showers, a bath, once a week was it. We actually had a copper bath in front of the fire and that was filled with a hose connected to a twin-tub washing machine. Emptying the bath involved making an actual siphon, there was none of this 'plug' and 'plumbing' convenience. Needless to say it was very easy to dry off in front of the fire and towels would be toasty.

Personally I prefer watching a fire to watching TV.