[mauricee]

I see R11 and R13 at the same thickness- 3 1/2". I assume there is less material in the R11, correct? Also, my understanding is that insulation bats should not be compressed or they lose the rated R value, correct? So both R11 and R13 need a space of at least 3 1/2" depth. If a contractor told me he would frame a wall with 1 1/2" depth with R11 fiberglass insulation this would be wrong?

[ma0641]

Yes, that is too much compression. For that depth use poly foam, double 3/4"or similar.

[creahands]

Check the r factor on the poly before buying. Like fiberglass it can vary even if thickness is the same.

Chuck