I have recently purchased an older frame home and have had it moved to our week-end property. My question is; what is the best and most economical insulation to use on exterior walls when the siding is "105" pine overlap and there is presently no insulation? We are going to strip the drywall off the interior of the outside walls which will bare the 2X4 studs. The weather is very, very hot most of the year, just a few days of cool weather and very little rain. It is in the desert of south Texas. We will have central cooling and heating. I don't want to take the siding off.