With plentiful, cheap energy, I suppose there was not too much concern for adequate insulation prior to the gasoline crisis.
Our church has evidence of several kinds of insulation, the horse-hair connecting fibers added to the lathe plaster on the walls and the more contemporary wrappings around the serpentine air conditioner ducts in the ceiling.
The funniest however, is the 1948 newspapers which were stuck under the window sill of the repair to one of the windows on Ward Avenue. It's possible they were left there as a time capsule, but more likely just something to fill part of the gaps which were left all around the window.
My dad read the New York Journal-American and the New York Herald-Tribune. I think we had the Journal American delivered by a paper boy for a while. Wikipedia, of course, details the travails of both papers and their demise in 1966.
We'll do some checking of the parish expense ledgers from 1948 and see if we can find the contractors and further details about the scope of their work. It could be the year the windows were all reset and the new layer of siding was affixed. Some parishioners might have pictures of the church from this period to help with this dating; let us know if you've got a documented exterior photo from the 40-50's and whether or not the original siding was in place at the time your photo was taken.
Stuffed away under Holy Cross window -