Polycryo ground cloth alternatives

Painter's drop cloth from any hardware store works really well. You can get it in varied thicknesses, and the smaller packages get you about 12 x 9 feet of it for around $4. I use 2mm for sleeping on out in the open on granite and find it durable enough. Cut to size, and you're good to go.

I second what Kari said about the painter's drop cloth.

I got a box of 9' wide, so I just pull out the width I need and cut there. Lasts several days and weighs less than an ounce (for a 3'wide piece – perfect for a bivy). Just cut a piece longer and double it up for longer trips (more durability).

Window insulation film at the hardware store. Painter's drop plastic gets holes in it too easily.

I would section the window insulation suggestion. I found that material much more durable than the typically 2mil painter drop cloth.

–mark