i blew in loose cellulose in attick and walls (there was previously NO insulation in the walls at all!). no vabour barrier as there was none previous anyway. heating bill came down so much that i made the money back in one winter
here are some pointers to remember about blowing in your own insulation...
when the insulation is pumping through 100' of hose it builds up one hell of a static charge. it can be so bad that you feel noxious or light headed. also, i was wearing a watch that stopped working because of the static electricity build up. so take off your watch & cell phone!
also you must clean the air vent on the blowing machine every now and again.
the machine itself is heavey as hell. you probably want to leave it outside while you run the hose inside your house (or outside if you are insulating from the outside). so pick a day with good weather.