R is the fraction of heat loss compared to an air gap the same thickness.
So R-19 insulation will conduct 1/19 as much heat as an air gap the same
thickness. If you place two pieces of insulation on top of each other you
can add the R value. For example two 6" fiberglass bats (R-19 each) equals
R-38.


"cece e." wrote in message
news:a7e539f1bc9dfc6800930e84a7875f5d@homerepairli ve.com...
My last question before I get started with insulating my crawl space.
Remember this is my first time doing this. What does the "R" mean for
insulation. I was going to insulated my crawl space with fiberglass
insulation but a man from the big orange box told me that for a crawl
space I could use (i forgot the exact name) styrofoam and glue it to the
walls and it would have an R10 rating (or something like that). What did
he mean and is styrofoam just as effective as insulation (in Colorado) for
keeping the heat in?