Answer:
Renovating an existing building can often be more cost effective and sustainable up front. However, what seems like a more affordable option might not always be the best choice when weighed against long-term goals or other factors. For example: possible system upgrades, the cost- long term and short term, the location, the building history and structural integrity, the intended use of the building and the potential hazardous materials.
Building from scratch might be the more costly option, but it comes with several benefits and can be less restrictive than renovating. These include: environmental sustainability, modern technology, more options, more efficient layout and less maintenance, and partial deconstruction.
There is no one correct answer and the decision will heavily depend on the circumstances. Every situation will have different challenges.