Thanks for your responses.
It would only be a "living space" in the idea that the temperature would be comfortable to walk up there for any length of time. I understand what you're saying about the load bearing potential of the floor joists. I'm not looking to convert into another room, just a clean space I can store some boxes, maybe Chirstmas decorations. I'm fairly certain the joists are able to support the few hundred pounds I propose, but I probably wont put plywood over the entire floor. It would sure make running wires much easier too.
Do a little web research on green building sites or building science, not a radiant barrier salesman though.
Ha! Thanks for that. I'm never one to jump along with the bandwagon on anything-especially from salesmen...if that were the case, I would have already torn out all of my old windows and put in pocket replacements. The same reason I don't quite buy into the spray foam idea....talk about expense....and funny I can't find anywhere that mentions how long it lasts-does it break down? Some sites mention they are stable "over time" but how long is that these days...20 years? I've already read that the bubble wrap insulation isn't as effective as the foil type barrier, but I'm still exploring this possibility. So far it looks like about $120 in foil to do my attic.
The house has already been given soffet venting...but I am concerned about trapping moisture. I'm looking into foam baffles. Either way, I'm fairly sold on getting rid of the old insulation---I have a lot of wires to run since I'm also sold on rewiring the house (why would someone tear out all of the plaster walls, then not take out all of the old knob and tube? Oh... those are the same people who decided not to connect the plumbing vent to the main stack, and leave the old tub drain open/dead ended under the sub floor. But I digress).