Construction Research has shown that from an energy perspecitve the reuse of an existing building is far better than building anew. This is mainly due to the fact that many building materials and products not re-usable and they need to be produced, transported and processed, whereas they are already present in the existing building. It is important however in that case, that this building economically and ecologically adaptable to modern living/working comfort.
The equating of an existing building for re-use against new construction can conflict economicaly, although in practice we have different experiences than previously theoretically believed. It is important is that the shell is structurally in good condition.
We saved a Listed Buiilding villa in Breda from demolition, by demonstrating that a new contstruction was more expensive than renovation. Part of the motivation was emotionally supported, because of the beautiful appearance of the villa and the specific details, which you do not find in new constructions.