A
Painting this one! Haha. I actually just finished building a pretty awesome treehouse... I think I am going to take a break. When I sold my old coop where this one sat on craigslist, it literally sold in 1 day with like 20 emails about it... which told me there is a lot of demand here in Charlotte. So I think I may build some nice looking 4x4 coops for people here just to keep busy.
I used 2" trim nails (a lot of them) on the siding. If you look at my interior pictures and the framing, you have to plan 2x4 nailers though so you have something to nail into. That's not hard, you just need them regularly spaced.
As for "trim" the window and door surrounds, etc. are all also those 1x6 fence posts! I just ripped them down with a circular saw (usually in half) and used that as my trim.
For the temperature, I don't really know northern coop building to be honest, you may want to ask someone like @aart about that. That said, with the lap siding (overlapping the bottoms and tops 1/2 inch) there are no gaps, so there should not be drafts if you had a solid bottom.
[/QUOTEappreciate your help. I do think you’d have people waiting by the door if you sold these down in your area. Up here in Wisconsin, for a basic custom coop it’s around$1,500 and not as cool as yours.