Here's a great thread about converting a metal shed into a coop.
https://www.backyardchickens.com/threads/from-tool-shed-to-coop.1321135/
Big roof overhangs for under-eave ventilation would be good for your climate.
https://www.backyardchickens.com/threads/from-tool-shed-to-coop.1321135/
If you can, you should.tearing it down and starting from scratch may be the way to go.
Big roof overhangs for under-eave ventilation would be good for your climate.