Hi,this whisky4 I have a 1924 craftsman house I in the process of refurbishing,I will be doing the roof,i.e. new sheeting,shingles,insulation, my question is when I do the insulation will it be best to put soffit vents down by the eaves and how many,also how much blown in insulation materail is best to put in as far as thickness i.e. 6"or12",also will be doing under the house,what is the best insulation to put between floor joiststhank,s whisky4

Insulation requirements vary in different parts off the country. My rule of thumb in below zero Illinois is to use as much insulation as I can properly fit into the opening. Your roof/attic does need venting but you can't just add vents at the soffit. You also need to allow the air to rise and exit the roof at a high point. A good roofer will tell you more about ridge vents and the like but you need both. Be very careful to not let the new insulation block the air flow where the soffit and the rafters meet near the exterior surface of the house. You must mainatin an opening about the size of a shoebox in each opening.