Insulating crawl

[Hatter]

I am building an addition on a crawl and I wanted to get some opinions. First, I believe you can insulate the crawl on either the outside of the wall or the inside of the wall - what would you recommend? Also, If you insulate on the inside of the wall with foam board, do you need to do anything for fire barrier(i.e. drywall)
Thanks

[Wgoodrich]

Depending on your geographic location the R value will change. However the installation method is normally pretty close the same all over the country. If you insulate outside you may but you are only allowed to insulate on the outside up to the finished grade maintaining clearance from untreated wood and siding if in a termite area.

In the crawl space you are required inside the crawl a vapor barrier on the crawl floor then you may insulate to the floor joist with styrofoam.

If you insulate on the outside limit is finished grade leaving an area above finished grade required to be insulated on the inside of the foundation wall. Might as well install all in one piece in the crawl space around the perimeter.

Remember to cut out for your vents in the crawl.

No fire break [aka drywall] is required in a residential setting over the styrofoam in the crawl area.

Good LUck

Wg