I've created these tables as an aid in predicting insulation costs when you are trying to make decisions about your building. I
wouldn't base your budget solely on these charts as costs will vary by region and installation prices are very sensitive to the degree of difficulty of the application. Think about the difference between installing in an attic with a 10 foot ceiling and installing in a 2 foot crawlspace with a dirt floor. Keep in mind also that most insulation companies have daily minimums that they must meet so these prices won't be correct for projects that are only a few hundred square feet or less.
To calculate the total cost of an insulation project use the $/board foot column.
A board foot is 1 inch by 1 foot by 1 foot. In other words, it is a square foot by 1 inch thick. So to figure the cost use the following equation:
[square feet of area] x [inches of insulation thickness] x [cost per board foot] = [total cost for the installation].
$/R-value column is the most accurate way to compare insulation types. It puts all insulation systems on the same level.
Structural insulation systems combine both structure and insulation in one and are becoming more and more popular for their airtightness characteristics, strength and high R-values.
Hybrid Systems take advantage of the best characteristics of an insulation system such as the airtightness of foam and the low cost of fiberglass. Flash and batt is becoming so popular that some insulation contractors are beginning to specialize in it. I am a believer, I used it in my new addition in 2008. Be careful though, make sure that the foam is not sprayed so thin that moisture can condense on its surface on very cold days. I live in the northeast and I recommend at least 2 inches of foam.
Joe Lstiburek, a prominent and very pragmatic building scientist in Westford, MA has gone on record recommending 1.5 inches of foam for the same region.