Most cost effective insulation?

blown in is much easier for this situation than is batt, and the store which sells the bags of cellulose will rent or loan a machine to blow it in. I'd look at the machine first, to see what kind/size of nozzle, then stare at the house a few minutes, and see how much damage you'd do creating openings near the ceiling for installation. If the house has no insulation, there probably aren't fire blocks, but you'll have to do several cavities -- the studs themselves are barriers. Probably there's a crawl space -- look underneath for insulation. If needed (count on it -- it will need it), it will have to be batts, and it will have to have gravity support. If you do this, I'd start with foam to seal wire and pipe s at floor. Also go around exterior looking for holes to foam. Put clear sheet polyethlene (I like 6 mil) over the windows outside, and staple it using screen mold or similar, to keep wind out of the window cavity. Check elec outlets and light fixtures and switches, too, for leaks. Foam works well there also, and/or you can buy black foam rubber gaskets precut to put behind the plug plate covers.