Insulating a modular home

Tom
I was amazed at how little employees of home improvement supply stores
new about proper amounts of insulation when I was preparing to add
insulation to our attic in our 4 year old modular. I could actually see
sheetrock when in the attic and all the rafters. I researched online and
found I should have at least R49. No one I spoke to could tell me that. I
ended up adding 32 bags of blown in insulation. My next project is to
insulate the crawl space, since I notice snow doesn't stay long near the
foundation. I can stand up under the house on one end and have to crawl on
the other end. It has pea stone over plastic on the ground. It always above
45 degrees. We have a computer controlled propane furnace underneath. I
think the info I'm reading says I should have R19 on the walls. Is this
correct? Is this 3" of styrofoam? Should it be foil faced? What is the best
way to attach it to the inside of the foundation? Thanks for any advise
you have.
Rick

Hi Rick,
If you are using Styrofoam, which is the blue insulation, it should be 4
inches. There are similar types of extruded polystyrene (which is what
Styrofoam is) from other manufacturers, which are pink, green and gray!
The foil faced foam (polyisocyanurate), which is yellow, should be 3 inches.
You are on the right track with R-19 minimum.
Tom