You are joking, aren't you?

MBQ

Yer'Know .... I'd started to answer that posting , using almost the same
words, then; instead of hitting 'SEND' , I hit 'CANCEL' - thinking ;"they
must be joking!"
I suppose such people have the vote?

Erm, nope. I wasn't joking! (Although I admit it does sound a
particularly dense question!)

I lived in a house with a fake fireplace for 20 years, and for some
reason it just never occured to me that the chimney in our new house
was open to the elements.

OK, so I will open myself up to further abuse:
Why do we need a vent in the wall, as well as a chimney?
How do people stop precious heat escaping up the chimney in the winter?
(Presuming we never / rarely have a fire in there)