My house was built with vents, un-closable, always venting vents. Inside temperature equals outside air temperature plus a little draft as the air moves from inside to outside and outside to inside

Heating or cooling is economically impractical, except in two rooms, one with no vent and one with a vent blocked with foil

I look forward to a knock down/rebuild where the future house will be will insulated and will exchange air with the outside in measured, heat exchanged doses and solar powered air con can heat or cool the house in peak solar generation and the house will be pleasant the rest of the day and night. I'm comfortable in 18°C to about 26° in winter and a little offset upwards in summer, and it's pretty easy to build to not gain or lose more than 8° in 18 hours in my climate (lows in the single digit negatives Celcius; highs seldom more than 40°C)