That can be done via the drop command(particle generator), or by placing a Fire object inside the chimney. For starters, try this -
Find the Fire object in the editor(Under the Empty/Objects catagory), and type this in the init field of it -
this setpos [getpos this select 0,getpos this select 1,5]; this inflame true
Now, replace the 5 in the above text with the height of the Fire.
Finally, place the Fire object so it's relative to the chimney of the house.
That's one thing you could try.