HGA Architects in MInneapolis just did the rehabilitation of an historic Ford manufacturing building with large, restored, steel sash and interior storms. Not sure how easy or costly it was, but it was a Tax Credit project, approved by Minneapolis HPC, etc. I'm sure you can contact them thru their website and someone would get back to you.
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Charles Liddy FAIA
Principal
Miller Dunwiddie Architecture
Minneapolis MN
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