Windshirts and insulation

AYCE from Thru-hiker once tried a sleeping bag with a noseeum outer, and then a bivy sack that went on top of that, I suppose you get supreme breathability + built in ground protection, and you could also make multiple bivies and have different fabrics like EPIC, eVent, and uberlight nylon. Would probably work well with clothing. Another advantage is easy replacing of the sub parts, the first rip in my down jacket is going to be tearful.

Dale,

In the early days of the Cocoon line, I built a handful of them with noseeum mesh outer shells, with the idea of (1) reducing the weight and (2) relying on a windshirt as the outer shell; I agree with your redundancy assessment.

We tried this with quilts/bivies as well.

However, the very reason insulation works – the creation of dead air space that can be warmed – is the very reason why an outer layer of "mesh" sabotages it.

When you move (which is all the time, even when sleeping), convection pumps all that nice warm air out of the shell, and into the space between the mesh and the windshirt.

The result was an insulating piece that while looked reasonable on paper, was a miserable failure in the field. These systems – both clothing and quilts – were a lot colder than their shelled counterparts in the absence of wind shirts (or bivy sacks), because, I think, there is far less resistance to convection in these two-layer constructions.

How about wearing a windshirt over a length of synthetic insulation like this guy.

Ryan you said , "in the absence of wind shirts (or bivy sacks), because, I think, there is far less resistance to convection in these two-layer constructions."

but I believe Dale is talking about using your wind shirt or bivy as the shell layer. Going without a solid shell I think would be useless, but if you are carrying just the insulation -like in the shape of a quilt, and only used it with a bivy -wouldnt the bivy act as a shell?

I was only thinking of using it in conjunction with a matching wind shirt– again, a system approach to make it marketable. Nearly every clothing item is sold as a stand-alone product and at this point, the weight won't drop much more until mated systems of clothing are made.

Imagine a Cocoon like shell with some sort of large diamond-pattern screen bonded right to it– just enough to protect it while sliding on the outer windshirt shell. You could turn it inside out for stuffing and storage.

I'm sure an insulated garment with no outer shell would be just a bad decoration– the heat would pour out.

Down would be harder to deal with. I was thinking of insulating materials that come in bats. I guess you could go with the lightest material that is down-proof.

I was thinking that all the perimeter areas would be rolled over an inch or so to give some toughness to those wear areas– collar, cuffs, zippered openings and hem. The sleeping bag concept is dealing with the same issues– if you are going to use a bivy, there's no point to the outer shell on the bag.

It is problematic how much weight would be saved against the durability. It would vent well and dry quickly.

It's not too hard to imagine a good poly insulation with some sort of outer layer built in. Another step would be a complete fabric with lining and outer layer all bonded together that could be handled like fleece and simply sewn with a serger.

I was looking at an army surplus liner for a field jacket yesterday. It has a typical lining and polyester bats sewn with an hourglass sort of pattern and the outer layer was quite thin and very breathable. Take that as far as possible and you have a Thermawrap style layer with the porous shell.

Maybe some of our MYOG sewing folk could estimate the weight savings– 20%?

Two things come to my mind. The first Ryan already mentioned which is you want to keep your dead air contained, so you want a the interface between the down or high loft insulation to minimize air movement which is most effectively accomplished by having a real shell on the garment / bag / quilt. The other thing is that in our lighter gear the fabric used isn't not completely windproof. This is actually a good thing because it improves breathability and comfort in most cases, and can be upped by doubling up (the insulating vest/jacket + semi air permeable windshirt).

–Mark

I think Ryans response was assuming a windshirt or bivy was used over the mesh covered insulation layer. I think he's saying the larger dead air space makes the combo colder than a typical garment / bag being used without a windshirt or bivy.

Ryan said: "When you move (which is all the time, even when sleeping), convection pumps all that nice warm air out of the shell, and into the space between the mesh and the windshirt."

One idea that Ive always had for SUL insulation was to take the liner fabric out of a sul jacket and use a windshirt or fleece in place of the liner.

…

I know they make quilted thinsulate and a few other synthetics quilted so they could be cut and glued.