Re: using tarp under tent in winter necessary?

Tyvec (the house wrap stuff) makes a dandy "footprint" and, unlike plastic, doesn't seem to be as ready to rip. I get it free (when needed) by stopping at construction sites and (after asking) taking the discarded bits. Sure, it'll say "tyvec" or "lowes" on it - but who cares - it's going under your tent!