I own a 2-story house in the NW suburbs of Chicago that was built in 1868 (old by midwest standards, still young by original 13 colony standards). I was up in the attic two weeks ago, looking to lay some R19 across the top of the existing R13 insulation between the ceiling joists. However, I looked down between the joists at the end of one of my gables, and I was surprised to see nothing - no insulation - all the way down to the basement sill!

So, I got three bids for adding insulation in between the exterior joists by the usual method - drilling a hole and filling in the cavity with insulation.

The question I have is this: The bid for AirCrete Foam insulation is TWICE the bid for pink fiberglass insulation. For a complete two-story house, this amounts to several thousand dollars difference between the two methods. Is the foam method worth the extra $$? Is there a large enough difference in the R-value between the two methods to make the difference in cost worthwhile? I assume that the foam does a better job, but is it worth several thousand dollars more?

I'm willing to pay the difference if you people think that it is worth it. What are your thoughts?