Zone 5, slab on grade foundation. I’m wondering if it would be worth the ~$800 to blown in cellulose in my raised floor. The top of the slab is even to grade, there is a perimeter of 2″ EPS around the house that goes from grade to 4ft down, then I put R16 amvec slab insulation down which has a built in vapor barrier. I got my home run pex system run under the floor system recently and realized how big of a pain it will be to put pipe insulation on all of that. Wondering if I should:

1. Leave the hot water lines completely uninsulated and hope that being sandwiched between an insulates slab and subfloor will be fine
2. Not be lazy and spend the ~$100 on pex insulation and try my best to wrap as much as possible
3. Just blow in some cellulose. 

My concern with #3 aside from not having it budgeted is if moisture would be a problem. Since the vapor barrier is just built in to the pieces of interlocking foam, we aren’t talking about some high detail stego wrap with tape install, and there is nothing but 2″ of foam and a PT skirt board on the edges. On one hand I believe insulation doesn’t hit diminishing returns until R60 so adding inches of cellulose would theoretically make the house more comfortable, but could moisture get in there and cause mold or other problems?