mylar type blankets

Howdy everyone! I'm thinking about how mylar type space blankets work, and would be grateful for any thoughts you might have. I'm wondering if there would be any decrease in performance in retaining heat by featuring a layer of fleece material between the mylar layer and the wearer. Specifically, if I were to sew a fleece backing onto the mylar side of something like the Grabber outdoor tarp, would I lose any of the heat trapping properties of the mylar? Thanks for your feedback.

Because the Mylar is a vapor barrier you would be better served with any additional insulation place outside the blanket.

For heat retention I think the fleece worn towards the skin will keep you warmer. You need airspace between you and the reflective film to make it work and the fleece provides that. I've used these blankets this way and they work amazingly well.

If you want to reduce moisture you could cut slits or poke holes in the mylar outer shell so it can breath.

I'm not sure I'd sew it. I think I'd try a very light coat of 3M spray upholstery glue first. If I sewed it I'd use fiber reinforced tape on the mylar where I intended to stitch it.

I was thinking more along the lines of stitching the fleece to the outside edge to retain the waterproof nature of the tarp. Spray adhesive is a good idea. It's more about creating a multi-use 'utility tarp/blanket' than to mock up a bivy.

On the other hand, the waterproof aspect could be satisfied by something like Tyvek, without mission creep. The mylar would need to be slit, and the final sandwich would be Tyvek/Mylar/Fleece. Stitching the fleece to the mylar wouldn't be an issue since the mylar needs perforation anyway. Spray adhesive between the mylar and Tyvek seems like it might clog the vapor permeability of the Tyvek.

Tyvek isn't waterproof in the slightest. At best, water resistant. I have a tyvek tent - best tent around if you are trying to eliminate condensation. Never had a drop. Worst tent if you are caught in a heavy rainstorm - filled the bathtub floor with water once upon a Pacific drencher.

I'm having a hard time figuring out when such an item would be more useful than the individual components. Care to share what it is you're really trying to accomplish?

I agree that two separate pieces allow for more flexibility. I was curious as to the effectiveness of the mylar under another layer.

Anticipated uses of tarp/mylar/fleece sandwich include:
- Picnic blanket for wet ground
- sleeping bag pad, for warmer seasons
- additional blanket (with separate pad, for colder seasons)
- emergency winter blanket for the truck

In particular, the industrial aesthetic of the mylar is not very picnic-y, and the other applications would benefit from the fleece as well.

I guess it would make it faster to deploy, but that's about it. It won't work for a groundcloth well. Punctures and tears too easily and once it starts it's not worth stopping though if it's glued to a piece of fabric that would stabilize it I suppose. I wouldn't purposely put holes or slits in it, but you could run into condensation issues over extended periods. Sounds like a good experiment for you to do. Thanks for volunteering!

The silver emergency blankets they sell at Walmart will tear to shreds if they get a puncture, but the SOL blankets won't.

On the downside, the silver reflective on the SOL blankets wears off. The Walmart silver blankets won't lose their reflective surface.

I believe the Walmart blankets are made from "Mylar", which is a brand name for a type of plastic, not all of which is shiny and reflective. It's not very stretchy, but it tears easily.

The SOL blankets are made from high density polyethylene (HDPE). It tends to stretch instead of puncture and tear.

SOL makes several kinds of reflective blankets, some are quite a bit heavier than others. Those heavier blankets might make a decent ground cloth.

I use a piece of bubble foil insulation with a reflective side for a ground cloth. I also fold it up and use it for a sitting pad. A piece of that with a fleece blanket over it would be pretty nice to sit and lay on.