I saw all this talk about using tyvek some years back and ordered a piece, but it was massive, heavy, bulky, and then when I read about how non water resistant it is, particularly the lighter variant, is that 1433?, which you can quite literally see light through the holes if I remember right, I just put those away as an experiment. I, probably like many others, didn't believe polycryo would or could work, but it did and does, all I do is hose it off over a clothes drying rack when I get home and dry it and that's that.
I do of course clean the spot first of sharp pricklies, but I always did that so it's not a difference in use.
tyvek would be tougher for abrasion I think, but I just haven't found any circumstances where that toughness would be of much use to me.
1.5 oz for polycryo, 5.5 for tyvek regular housewrap, you're right, not quite 4x heavier, only 3.6x?. Tyvek is too noisy too. If I want a tougher ground cover I'll just use a simple sheet of coated 70d nylon, it's not that different in weight from tyvek, and it's more pleasant.
I really didn't believe that polycryo would work, and there's probably some cases where it's not great, like being pitched on solid rock for example.
I got some of the lighter, kite type, tyvek to check it out, but when I saw that it had basically zero hydrostatic head, ie, it has visible holes in it, I decided that was it for tyvek and me. Maybe for cowboy camping where you have no tent floor? I don't know, I guess it has use for some people, I can't see it myself though.
Ron, nice to see you factor in the sustainability/durability component too, that's something it is often ignored with ul gear. I just treat these as if they all basically are made out of oil, so whatever the weight is is roughly how much oil it took, give or take, crudely. That's somewhere lighter materials do better too as long as they are not disposable, most people don't wear their gear out, they usually just stop or don't use it enough to wear it out.