insulating with foam sheets

[Albert Skye]

This thread is for general discussion of the design and construction of insulation made from foam sheet (whether it be Insultex or one of the various polyethylene/polypropylene materials made for shipping/packaging/&c.).

Foam sheet appears to work well for insulation, especially when two or more layers are used and those layers are separated to minimise heat conduction. MacEntyre has been using pleats (InsulTubes) but I think there is opportunity for improvement.

Using a separate layer of expanded mesh made from foam sheet seems promising. It's labour-intensive (though easily tooled once the dimensions are optimised) but I think it would work well.

Alternatively, the layers could be separated with a replaceable air bladder (plastic bag), a little down, found materials (dry leaves/grass), by direct inflation (assuming airtight material and construction), &c.

[LostCause]

I don't have anything to add other than I think your idea is interesting and would like to see how this develops.

[Stovemandan]

Great idea!!! This material should work between the sheets to create air gap:

http://www.ruralking.com/6-in-x-20-f...30353830303436

[WV]

Yes, indeed! Very promising. What's the scale of your photo? How long are the slits in the expanded mesh? Do you think slits as long as 6" would work?

[Zac]

Maybe use a foam or pvc shelf liner. Kinda like a http://www.stacksandstacks.com/shelf-liner-grip-it

[turnerminator]

I have always been impressed with the added warmth that windscreen sun-shades give.

At 70g each, they seem to punch well above their weight. 4 of them weigh about the same as a thick ccf pad, but seem to offer more warmth.

A hammock sized thin foam layer with a layer of aluminised mylar glued to it, then a layer of foam mesh stuck to the mylar?

I'm thinking that the solid foam at the back of the mylar would stop heat conducting from the aluminium to the bottom layer of the hammock and into the air. The foam mesh would allow the thin layer of air to be kept between the mylar that is needed to make this kind of insulation more effective.

[Albert Skye]

Stovemandan, Zac: My aim is to minimise weight and volume, and increase flexibility; i.e., both of the suggested materials are far too heavy for me. In any case, it's very easy to make expanded mesh.

What's the scale of your photo? How long are the slits in the expanded mesh? Do you think slits as long as 6" would work?

I've not made any experiments yet (perhaps better to leave that to others with proven testing skills ) but I have seen that if the pitch (spacing between slits) is too small, or the slit length is too long, the mesh tends to flatten. One solution is to use a slightly thicker foam, perhaps 2 mm. It need not be closed-cell.

I have always been impressed with the added warmth that windscreen sun-shades give.

[...]

A hammock sized thin foam layer with a layer of aluminised mylar glued to it, then a layer of foam mesh stuck to the mylar?

I'm not sure exactly what kind of product you have in mind; most of the sun shades around here are aluminised bubble sheet.

As I understand it, most materials reflect IR, and I imagine the white PE/PP has high IR reflectance but it would be good to know for sure.

[MacEntyre]

I used a nylon mesh on the inside of my Thermadrape KAQ that I sold to Rilmoigan. The mesh is same stuff that is used for athletic jerseys. It's a little heavy, but I believe it performed just as you suggested, Albert.

- MacEntyre

[WV]

I took a 60" x 60" piece of Insultex and used the sewn diamond grids to locate slits (folded the IX and used scissors to cut a slit in each diamond). Here's a photo. I hung it on my grape arbor to see how much it would stretch. I'll use it as the middle layer of full length Ix UQ, 45" x 75". If I had cut the slits a bit longer it probably would have stretched even more, but I didn't want to weaken the Ix too much. I will probably use some of the adhesive transfer tape that I've been experimenting with to tack it to the top and bottom layers so the UQ will maintain a consistent thickness (bottom layer won't sag).

[MacEntyre]

That's very clever, Dave!

Did you notice that IX is stronger in one direction than the other? Stormcrow pointed that out to me...

You should slit it in the direction of the strength.