Floor plan with internal pantry - What to consider?

The base slab or the floor will not be provided with expansion joints either. The heat from the surrounding surfaces is sufficient.

We planned it with exhaust air. It was like that in the old house too.

my experience with exhaust air: a small catastrophe for food, which quickly loses moisture. For example, mandarins become so shriveled within 2 days that you no longer want to eat them. And this in an open space, which has supply air on one side in the living area and exhaust air in the kitchen area. I only store fruit/vegetables in the utility room anymore (if not in the climate compartment of the fridge), there is no heating or controlled residential ventilation installed.

Adjacent to the pantry, there will probably also be a chimney running, which also generates waste heat. Is that a problem?

Counterproductive. I would suggest, for you, to create a storage room (instead of a pantry) and to plan for an additional 60 cm cabinet in the kitchen for your food.

We also left out the underfloor heating in our pantry. In hindsight, it was a mistake since our heating system can also cool. So it happens that in midsummer the temperatures are moderate everywhere except in the pantry. :rolleyes: We are now considering retrofitting the cooling function through the ceiling.