how did orthodox jews heat their home over shabbat if they were not allowed to tend the fires?

when using a modern stovetop flame;
on shabbat we can’t adjust the flame at all, nor turn on:off
in addition many consider the flame controls to be muktzeh
on yom tov we can adjust the flame, nor turn on:off

it occurs to me that over a century ago observant jews
living in cold climates had wood or coal heat at home
the home itself may not have offered much insulation
and it’s unlikely anyone could go 25 hours without having
to feed it more fuel or tend the flame in some other way.
multi room homes could have multiple heat fires going.

so how did jews manage this heat – without breaking an av melacha?
and don’t tell me they all employed shabbos goys or had kids do it,
as not every orthodox jew was affluent or had some kid on hand.