A few questions about building a new room

We are moving into a new house the 15th of next month and my wife has given me permission to considerably increase my collection and my snake room size:D Its going to be in my basement and I have a few question for anyone else who has build a room (Or even if you haven't but know something I dont)

1. What do you do about flooring? Its in the basement and the floor is concrete and I use room heat..So I do not want to suffer really bad heat loss through the floor.

2. Ventilation..Is it more about air circulation (aka fans) or more about air filtration?

3 Finally I am building racks..Is melamine really okay (as long as it is well built) or is shelling out the $$ for xpvc worthwhile?