Saving Notre Dame follows various experts as they study the components of the cathedral's iconic structure to puzzle out how best to repair it.

Director Joby Lubman was among those transfixed in horror when the fire broke out, staying up much of the night as the cathedral burned, until it became clear that the structure would ultimately survive, albeit badly damaged.

"And it might sound opportunistic, but I thought, 'The restoration of this icon is going to be quite something to document.'".

Lubman and his development team reached out to the appropriate authorities, and within a few weeks they were sitting in on meetings with scientists, architects, engineers, and others combining their expertise to restore Notre Dame to its former glory.

"They were the original engineers, before engineering as a term existed," said Lubman.

Among the experts featured in Saving Notre Dame is glass scientist Claudine Loisel, who was relieved to find that the cathedral's famed stained glass windows were intact and not too badly damaged.

There were microcracks in some panels from the thermal shock of the fire, and most windows were coated with the toxic lead dust that was emitted when the lead roof burned.

For that segment, Lubman also took his film crew to York, where conservationists have adopted a new preservation approach to the stained glass windows of York Minster Cathedral.

The new approach involves installing protective clear glass external frames before replacing the original stained glass windows.

The gap between them improves ventilation and prevents condensation from building up on the original stained glass, as well as protecting it from damaging UV rays.