I have seen this question pop up a few times and I think the best advise is to set down with a budget, needs, wants and how big you think you will get. if you will only ever have a couple calves at a time and limited budget then 3 rooms will be enough. a dark room to keep the calves that may or maynot have ac, a well lit area that drains for clipping and fitting, and a storage room for feed and supplies. If you are going to be having sales or larger numbers with multiple people then you might need a seperate wash and clip room. If you have bulk feed or mix a lot of additives might need a pretty tight sealed room with a scale and mixing boxes and bulk feed storage. The designs, size, and cost are limitless. My original barn was on old milk barn with double wood walls made it stay pretty constant temp since wood doesn't transfer heat like metal. Had a feed room, The parlor was divided in half and used for the cooler and wash area. It had a drainage channel in the floor so made for easy clean up. Were the pumps and bulk tank sat was what I used for clipping. That was the only thing I hated about the whole set up not enough light or room to get a ways back and look at the calf while clipping. The new place the barn is similar with a few changes Bought an old wood garage and filled in some of the doors. put 2x6 wals in it and put 4 inch dense foam in the walls and filled the rest of the gap with wood shavings( got the idea from the old ice houses that would keep ice froze for months. They had 2 walls with the gap filled the wood chips from the lumber they cut.) I put holes in the concrete in the wash area to put pipes in the ground at different points depending on size to keep them from swinging back and forth. sloped the floor in the cooler to a drain channel so the whole barn could be washed out. Made the clipping area larger than before and put lights every were at different angles so there are no dark spots or shadows while clipping.