One of the more controversial issues with a Passive House is that chimneys are not really allowed. At least not masonry chimneys that span from the inside to the outside. That is exactly what we had, and it had to go...sniff.
The issue here is that the masonry is a really great thermal bridge to the outside. If you have a masonry fireplace, put your hand on the block some chilly night and see how cold it is. We have these things in order to heat our homes supposedly, but since the invention of central heating in the mid 20th century, they are more decorative and very seldom used. There are also air quality issues, maintenance issues, and other things as well that make them a bad idea...however everyone has to admit
We love fire! Who doesn't?! Communists that's who! So it was really hard to take down our fireplace chimney. Actually it was quite physically easy — another reason to not have a giantpile of sort-of-held-together bricks attached to the side of your house.
We think you should have fire at your house...but outside...in a fire pit. If you must have the ambiance of fire indoors, consider an ethanol unit. Portable options = fire without the mess.