I keep reading different sources and many of the posts about space requirements and nest box sizing. Haven't noticed any about how far off the floor to put roosts. The girls are Rhode Islands(12) and Golden Buff Cross(13). Just young'uns, but what is suggested for roost height and nest boxes. The pen is 7' x 12' in the old dairy barn. Used the 3 sq.ft. formula. Plan to make a run at least 25' x 25'. Also, will chickens go out when snow is on ground? They're living in NW PA .