Suspended Slab Balcony - Thermal Bridge

I am adding a second floor to a house in Sydney, supporting a concrete slab on existing double brick walls. Also adding a North-facing balcony / deck area that extends beyond the existing walls. I'm looking at two options:
1) Extending the slab to form the balcony, with some galvanised steel posts to add support.
2) Building a timber deck.

Hopefully will have variable shading on the balcony (and windows that open onto it) - adjustable louvre, or more likely (i.e. cheaper!) sailcoth that is removed in the winter.

The first option is the builder's preference - based on durability and reduced maintenance of concrete relative to timber. I am also a fan of low maintenance.

My concern is whether the concrete balcony will heat up and act as a thermal bridge, carrying heat into the house in summer. Does anyone have experience of this?