[boati]

it was ok at 50+F, for 2 hours, with just a t shirt and jeans. Tonight I tested it for 1.5 hours, at 47F dropping to 42F, with a heavy duty space blanket just folded around the modified SOL escape bivvy, with a tyvek bag around the total. Once the wife gets the sewing machine set up to her liking, i'll get the velcro seams on the space blanket, make the other tyvek bag (reflectorized) for the outside layer. Given the right clothing, it's going to work just fine down to 20F, perhaps even to 10F. It will reach 10F if you can stuff dry debris between the layers, dead rock certain. yet there's no stuffing to be lost, no zippers to jam or break, geting it all wet will have no effect on its efficiency. it can be set up as a tarp, as a hammock, or on the ground, with the gillnet hammock, bubble wrap and bug net bag acting as padding. pretty cool, if i do say so myself. it IS necessary to have the tyvek layer between the breathable mylar and the heavy duty mylar, cause even tho the breathable layer is not permeable, there's a sense of clamminess. the tyvek prevents that from occurring.

 

[Garand]

They only thing wrong with being cheap and cutting corners, it could cost you your life.

 

[Terry G]

Garand, your right! Actually buy decent equipment first. Now who would have thought of that?

 

[Garand]

Now who would have thought of that?

People that have actually been there, done that?

 

[BigBassMan]

Isn't Tyvek what is used for house wrap? If so it only has about a R1 value.

 

[John in AR]

Isn't Tyvek what is used for house wrap? If so it only has about a R1 value.

I'm a fan of "buy once, cry once" and of buying quality instead of recreating the wheel, but fwiw on insulation, the R-value is a much smaller component of effectiveness than most people realize. Easiest example is closed-cell foam such as styrofoam coffee cups are made out of.

Typically it runs from R-6 to R-8 per inch, which is much more than other insulations like fiberglas or cellulose, but think about the coffee cup. Other than the reinforced lip at the top, they're only 1/16th of an inch thick or so, meaning an r-value of around 0.4 which sounds just pitiful. Yet it will keep scalding-hot liquid from burning your hand. With an R-value of less than 1...? That's impressive performance.

Other factors that affect effectiveness of insulation include vapor/water barrier properties and draft-sealing. R-value is worth looking at, but it's not even the primary consideration imo, and certainly not the only consideration.

 

[BigBassMan]

Still not what I would want to make a sleeping bag out of even if there is three full an two partial rolls out in the garage.

 

[John in AR]

Still not what I would want to make a sleeping bag out of even if there is three full an two partial rolls out in the garage.

Agree, especially as the outer layer. Tyvek is good stuff and resist linear ripping, but is pretty susceptible to cuts and puntures. That said, don’t know what I’d prefer for a diy solution except maybe nylon or aramid perhaps.