On 30 Oct 2006 08:11:03 -0800, a particular chimpanzee named
randomly hit the keyboard and produced:

How do people stop precious heat escaping up the chimney in the winter?
(Presuming we never / rarely have a fire in there)

In traditional houses with open fires, they didn't. They threw more
coal on the fire and wore a lot more clothing away from the fire. In
modern houses, you either don't have open fires with open flues
(instead having your appliance within the room to maximise its useful
heat with ventilation close to the appliance), or at least make them
carbon-neutral (log-burning stoves).

Your house must have been built to the Regulations in force prior to
1995. It would be nigh-on impossible to get a dwelling with an open
chimney to comply with the Building Regulations of 1995, much less
todays.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"