Attic Floor Insulation

My attic is filled with loose fill insulation. The home inspector suggested that I up the R value. what is the best way to do this? Should I simply add more loose fill, or could I roll out insulation over top? Would there be any reason to remove what is there? If I wanted to make a storage area, should I replace the insulation beneath or simply nail plywood over top? Thanks

Well, my wife and I have decided to settle down in Japan. My wife is Japanese and her family has some land but it is farm land. We are now finding out how fun(satire) it is to rezone the land from farmland to house land. But my real question is about houses. We have looked at a variety of homes and it seems that many of them are quite nice. But some of them cut corners to make the price lower. Out of all the houses and companies that we have looked at we like Selco homes. They are imported 2x6 built homes from Cananda. They have solid wood floors, while 6 panel doors, vinyl windows and loads of insulation. They do use fiber glass insulation and some builders have told us to stay away from it as it can absorb moisture etc and cause problems. The builders are pushing a hard foam type insulation(expensive) but Selco does not offer it. How big of a difference is it? I am aware of all the humidity problems that many homes in Japan have. Should I go with the foam and choose another house or is the fiberglass OK? I understand the whole vapor barier idea. The Selco home wall is as follows from the inside out. wallboard-plastic vapor barrier-insulation-plywood sheeting-semi permiable sheet-siding Note: there is no space(air) between the siding and the permiable sheet. Some builders have stated that this is very important. Is this true? Does it matter so much. I would appreciate any pointers on what is needed to get a good decent home. So any opinions would be welcom. Thanks, Sdskinner