I'm going to be installing an engineered floor over a concrete subfloor which is on the ground floor of a building. I want to float the floor to save on some costs and am trying to decide what type of underlayment to use which got me thinking -- what is the purpose of underlayment when floating a floor? I don't have anyone living below me, so I'm not too worried about causing too much sound below. What else does an underlayment provide?