: Fiberglass is apx 3.75R per inch, foamboard goes from R 5 to R
: it costs alot. It depends if your old insulation was done
right, it may
: be fine but even if done right total R value is not optimal.
I'm slightly confused.
For the equivalent R, yes, it's more expensive for sure, but
not by several magnitudes. I got a great theoretical R with a 3"
thick board in the 2 x 4 spaces, For about 2.5 times the cost of
a roll of foil faced 3.5" insulation and I got an R of supposedly
20, plus a little if the air gap's right. Using two layers of
1.5", interestingly enough, would have cost me more, plus lost a
couple of points in the R scale.
So ... teach me here if you can: How is the total R not
'optimal'? It's really NBD since it's "just" a porch, but the
walls are actually almost warm to the touch, compared to our
front porch, which feels cooler and has 5.5" 'glas in the 2 x 6
spaces. So, I'd ass-u-me-d it was an improvement. Both are
heated BTW, and make "day rooms" for me (I'm disabled) when I'm
having my "bad" days. I'm coming at it from a $ to heat cost, of
course. Oh, one's an east, the other a west exposure.
Or am I not understanding your comment?