Chimney question

The fireplace and chimney is considered a big improvement over the ancient centrally placed hearth. I presume the draw of the chimney improved combustion and the brickwork helped radiate heat better. But my question is, why was the chimney and fireplace moved to the wall of a house, instead of remaining more central? Especially in light of modern indoor fire pits, which are more or less a hearth with a hood and chimney.

many were.

in old homes, when the thing started, they might be in the center.

chimneys for coal or wood were in house interiors.

in a smaller home or when a fireplace might be more decorative in might be moved to the wall.

It would seem natural to include the chimney in the structure of a house. If the main structure is the outer walls, chimneys go there. Most of the houses built here in the last century that were built with fireplaces for primary heating don’t seem to have them on outer walls. But this was a construction that had all brick walls, interior as well as outer. A common trick being fireplaces placed back to back in adjacent rooms that would share the chimney structure.

I have seen a Victorian-era house with central a fireplace.

It was a double-parlor house with a carved marble fireplace in the front (formal) parlor - it was on the wall.
The second was red brick in the wall between the rear (casual) parlor and dining room - it was facing the parlor, and was not visible from the dining room.

I have a central fireplace now. Exterior chimneys in the wall are extremely inefficient and became popular as an adjunct for homes with other means of central heating. External chimneys were sometimes built into the stone exterior walls of a structure though they might have an internal chimney as well. In warmer climates the heat from the fire used for cooking could be undesirable and an external chimney was used in the kitchen. In an unusual case there were sometimes chimneys constructed of wood, they were completely external and build with supports that could be pulled out in case of a chimney fire and the chimney would fall down away from the home. Until fireplaces became more decorative than functional the vast majority were internal.

just a guess, fires in exterior chimneys are less likely to burn the house down than a central chimney.

In 17c houses the chimney was often the only stone part of the building. It would be several feet thick and formed a substantial base to build around.

Big houses had dozens of fireplaces, mostly internal and the flues joined at the upper floors. There would still be a lot of chimney pots. like these.

Town houses were crammed together and often built in rows called terraces. The fireplaces would be on shared walls back to back.

I suspect that the evolution of the fireplace and associated chimney had a lot to do with fashion and cost. In a 20c house, built with common brick, it would be much cheaper and a more efficient use of space to put the fireplace against a wall. In my house (1950s) the chimney is inside on an internal wall. There would have been a coal fired stove in the kitchen which also heated the water and fireplaces in the sitting room and the bedroom above.

At the end of WW2 there was a crisis of housing and thousands of concrete prefabs were built. These were small but efficient (although badly insulated) but designed by engineers, and yes - the chimney was in the middle.

They were supposed to last ten years but people became very attached to them. here are some survivors, now listed buildings, not far from me.