I have an old home that had a closet "added" on to it at some point in time. the add on has three sides of exposed/exterior wall and none of it is insulated. It really makes a difference in the room's temperature. I'd like to blow insulation into the space b/w the wood siding and the drywall (about 4-5 in). Is this a diy project? How do I go about it? Can I rent a blower?