PipeDown wrote:
I want to insulate the bottom of the floor (inside crawlspace). The problem
is the floor joists are nowhere near 16" on center. My single story 1000SF
house is built on a deck like subfloor. It is made up of 4x8 beams running
the length of the house set 4 feet apart with 2x8 tongue and grooved planks
set perpendicular. The result is a thick solid floor with few beams
underneith.

To put it another way, the floor joists are 4 feet apart and the crawlspace
access is a 2'x2" hole in the closet floor.

I was considering 4x8 sheets of solid core insulating panels cut in half the
long way but this would be expensive and would not have as good R value as
fiberglass. I would need to double or triple up on them to get the same R

Has anyone seen a product that sounds like it would work well here or am I
stuck using 16" wide rolls and stapling in strips to the underside of the
subfloor instead of the joists. This is not ideal because it would compress
the edges of the insulation.

Do you think installing paper faced insulation with the paper up so I can
staple through it is a good solution?

Fortunately, I am in northern CA and the climate is mild.

The rigid insulation is the way to go - if you've determined that the
potential energy savings and increase in comfort is worth the expense
and effort. Since your climate is mild, 2" rigid insulation should be
fine. Go with polyisocyanurate insulation (~R14 for 2") if you feel
it's worth the money, extruded polystyrene (~R8 for 2") if not.

Since your floor is so thick you can just screw the boards in place
with some of those pancake plates that they use for EIFS and use some
expanding foam to fill in the gaps.

As an alternative, and not necessarily a great one, you could suspend
2x3s on 16" centers between the existing joists, then staple up
fiberglass batts or use those wire press fit hangers.

R