Bob & Bill, I believe that densly packed cellulose (3 - 3.5 lb/cu ft) is the best you can get unless you are willing to open the walls so that foam can be sprayed that way. The problem with trying to pump foam throught holes is that it is very hard to insure converage. Not that it can't be done, but the reality is that usually it isn't done right. This lack of coverage shows up dramaticly on an infrared video camera. Dense packing celulose isn't the most fun you'll ever have but it is doable. DP cellulose will form and air barrier thus perventing air from carring moisture into the walls. If there is high ambient moisture some will of course enter by diffusion, and a forced air furnace that pressurizes the house can also force moisture in to the walls. Any moisture entering, whether from the outside or inside will be held by the celluose (wicking it away from framing and sheathing) and released as the wall drys to the inside and or outside. At first, you might think this retention of moisture is not a good thing. But since the moisture is entering, it must go someplace, the alterantive is for it to condense on the sheating and run down to the sole plate with the obvious consequences. BTW walls with fiber glass follow the latter path since FG is incapable of wicking moisture. Of course if there is so much moisture entering that the wall cannot dry (or if the wall has no place to dry to because of finishing material choices) the celulose will be reach it's limit, but that will only happen when there is some serious moisture or pressurization problem that should have been corrected before insulating. For more info. see www.weatherization.com. For the experience of a first timer see www.fixerupper.com, "Weatherization" thread, message "adventures in denspack" (Feb 11).