PEX plumbing question

[poppy]

So I've been thinking that on my 1957 ranch house rehab project that I would put in a PEX central manifold/homerun system.

The house is on a perimeter block foundation with unheated crawl space.  The temperature can range from 0 to 100 F here is S. Ohio.

The original plan was to run the tubing under the floor, but now I'm considering running most of it through the attic.

I plan to blow in about 8" of cellulose for attic insulation, so it would cover the tubing.

Is this plan a good idea?     If not, why not?

[MountainDon]

Here in NM that is one way they do it when replumbing a house that is built on a slab. The more expensive way is to go through interior walls, around door frames, etc.

In our home the pex went through the attic more or less from one end of the house to the other and down into walls. There were still 14 cutouts in the drywall. All perfectly patched by the installers BTW. All pex in the attic was first covered with those foam pipe sleeves. Then bundled with zip ties. With all the pex in place in the attic the bundle was covered over the top with new R30 insulation batts, with the batts secured down to the truss bottom chords. An impermeable sheet was placed over than and also secured down to the truss bottom chords. Then the blown in cellulose that I had added a few years ago was redistributed over that. R45-50 total. From below three ceiling vents were installed directly below the pipe run. This was to help form a warmed/heated chase around the pipes. This all satisfies the insurance companies and anyone else concerned.