In the process of searching out ideas and plans for a new coop, I discovered this site by North Dakota State University Extension Service. It has plans for chicken and turkey coops, barns, feeders, nesting boxes, brooders, etc. I think you will find it very useful if you are planning a new coop or amending/expanding one you already are using.
Yeah, I saw that sun parlor, too. I figured that it being North Dakota and 1933, that it was a way to make a brooder that would save on heating costs. I have a friend, now 87 years old, who grew up in North Dakota - he didn't have electricity or running water until he was a senior in high school. I fear that some of the tales of his youth have colored my image of the wheat fields of the far north.