Mat booster

Tyvek and foam insulation? I can’t quite be sure what that is made of.

Tyvek is made of high density polyethylene.  HDPE has a thermal conductivity between about .45 and .5 (W/(m K)).  To put it in perspective, water has a thermal conductivity of about .6 and a little change.

Tyvek is not a good material to use for any kind of thermal insulation purposes.

Polypropylene would be much better with a thermal conductivity of about .1 or so, but very similar low density of HDPE.

“Tyvek and foam insulation? I can’t quite be sure what that is made of”
yes tyvek and the classic Blue Mat .
I had both at hand , the Blue Mat had bits missing from an insulated flash project I had previously made.
The Tyvek was simply used to hold the foam. I could not see myself placing those tiles one by one hoping that they would stay there during the night.

I could not see myself placing those tiles one by one hoping that they would stay there during the night.

Franco, you made me spit out my morning coffee 😂

and the classic Blue Mat

Thanks. That looks like a good idea.

oops – you missed one – upper left

The thing is, the Tyvek is providing some definite bulk and some definite weight, but almost no insulation value whatsoever.  What tiny amount of air it may still/trap within it’s fibers, won’t count towards much at all, and if it gets wet, whether from condensation, rain, dew, etc, then it loses what little air it stills.

And there is far too much space in the gaps between the foam tiles to contribute to much insulation in that sense/way. Any and all little movement on top, will convectively displace/circulate any temporarily warmed and semi stilled air.

While saves a bit on bulk, honestly insulation and weight wise, it would make far more sense to just use a larger area, thin EVA foam pad. Foam is quite insulative for it’s weight and bulk.

Anything that separates the users mat from the snow adds substantially to comfort but from an experimental POV I’d appreciate Francos comments on the extra warmth boost compared to being on the cold snow

If you’re looking for most insulation for least amount of weight, then a simple thin EVA foam pad cut to the size of the air pad, would work much better and be much more efficient insulation to weight wise as an adjunct to one’s air pad.  On the other hand, the tyvek adds bulk and weight with no noticeable insulation value whatsoever.

And this particular fabric looks like Homewrap or similar equivalent.  That is a bulky material to begin with (especially so for an otherwise thin material).  I know, as it was the of the first MYOG/DIY materials that I worked with.

And as earlier mentioned, once it’s pore spaces fill up with water, it actually becomes a moderately conductive material, because semi oriented HDPE is fairly conductive material.  Earlier, I quoted .45 to .5, but I think that is off.  I think it’s actually higher, because that is for HDPE in it’s more solid, plastic state, and these are somewhat oriented spun bonded filaments, which will increase crystallinity and regularity of molecular chains some (which increases tensile strength), thus increasing the thermal conduction over the base material.  It could be as high as 3 to 5 if the pores are filled with moisture, hence some 5 to 8 times higher thermal conductivity of water in the actual material itself.  

For a more extreme example, highly oriented UHMWPE (related base material to HDPE btw) fibers, such as in Dyneema and Spectra fibers, can have thermal conductivity (20) same as stainless steel (around 20)!

So yes, if you want a mildly weak heat sink below you, then use things like Tyvek. Good for those hot summer days–slightly wet the material and lay directly on it nekked, it might help to cool you down a bit. Course, being a thin material it’s not going to be much of a heat sink all in all.

From Ed
“from an experimental POV I’d appreciate Francos comments on the extra warmth boost compared to being on the cold snow”
By using the word “booster” I thought it obvious that it wasn’t meant to be a stand alone thing.
The idea was to have the main mat on top of the tiles giving it at least partial insulation from the snow.
I did have a thin (maybe 3mm ) Evazote mat but this one is somewhat similar in size but gave slightly better insulation for me.
The Tyvek helped keeping the sometime occurring wet patch under the mat away from the main mat surface.
As already pointed out I then opted to just use a thicker main mat (Exped 7) but this does work .

“I did have a thin (maybe 3mm ) Evazote mat but this one is somewhat similar in size but gave slightly better insulation for me.”

That is completely against the physics involved.  Unless this is some sort of consciousness/mind influencing matter type process (akin to placebo affect), then it doesn’t make sense, because it’s against the physics of the materials and insulation principles involved.

1. Tyvek=moderately conductive material, especially when the pores between the spun bonded filaments become laden with and the air in same displaced by moisture. Bare tyvek makes up approximately 50% of the total surface area.
2. Gaps between foam tiles are much too large to efficiently slow down convective heat loss. 

All this design does, is save a bit on bulk over a full foam pad, and provide some protection to one’s air pad.  It does not however increase insulation vs an all foam pad as claimed. From a physics-materials-insulation viewpoint, it cannot.  Only could from a placebo effect viewpoint/perspective, which can be real enough to those who experience same.

Btw, very interesting timing of this thread.  Consider the schooling in holistic logic 101 going on, a type of karma.

You haven’t accounted for the insulation which is provided by the foam pads so with them being ~50% of the surface there would be some value, I can attest to the value of an airspace above a frozen surface and even if the actual R-Value is small it isn’t zero. So 50% using 10mm foam is not as warm as 100% using 3mm foam?? Please explain

I am not following this logic too well. Sorry….

I am assuming you are discussing insulating value.

Yes 50% of 10mm is the same as 5mm? No. smaller air pockets, due to lower convection, are more heat efficient than larger pockets. This is why 900FP down is warmer for the same weight as 600fp down. This means that a continuous coating of small pockets is more insulating than a distribution of alternating, thicker foam.  Assuming the same insulating value for the foam, a 3mm pad would be roughly equivalent to the 10mm foam spaced out at 50% intervals over Tyvec. Tyvec, and other materials have way less insulating value due to it’s thickness, regardless of it’s conductivity. The thickness means there is little insulating value to Tyvec, nylon and poly materials. In most cases, you can ignore it since it’s Rvalue is so tiny. Even the manufacturer says it is NOT an insulator.  From DuPont:

“<b>Do Tyvek^®weather barriers have an R-value?</b>

No; however, properly installed Tyvek^® weather barriers help protect against loss of R-value in insulation due to wind washing. Even at wind speeds of 5 mph, a wall without an air barrier retains less than 40% of its original installed R-values.”

“You haven’t accounted for the insulation which is provided by the foam pads so with them being ~50% of the surface there would be some value, I can attest to the value of an airspace above a frozen surface and even if the actual R-Value is small it isn’t zero. So 50% using 10mm foam is not as warm as 100% using 3mm foam?? Please explain”

The foam tiles will provide localized insulation. Imagine a quilt on top of you that only has every other square baffle with down in it. The insulation in same, isn’t going to do you a lot of good, because of large areas of heat loss/leakage.

Now, the above will be slightly better, because at least you have an air pad over the large gaps, somewhat sealing them.  Somewhat better.

Anyways, my main disagreement is with the statement that this set up provided more insulation than a full 3mm foam pad.  

Just not possible according to the physics, materials, and insulation principles involved, unless it was a kind of placebo type effect, which certainly can and does happen, and as I said, can and does influence matter/physical bodies some.

How does Wim Hof do what he does, or what he has taught others to do?  Partly mental and physical training, but a good chunk seems to be something akin to what causes/allows placebo effect.

Ed,
I had to think hard about exactly why I made that booster mat given that it was over 10 years ago (I made it before the Tarptent  Moment came  out in 2009).
At the time I was using a Thermarest ProLite Plus, the W version. To that I added a pillow to get my size. To have some insulation on frozen ground I had to pump it up at max , however that was not comfortable for me.
I did have a thin Evazote mat cut to a sort of mummy shape (it was the base of the Down To Earth JRB system , I named it…) but that was still not enough to let some air out of the mat and not find my pelvis too close to the ground. So the extra thickness of those tiles helped with that and  still resulted into a low stored volume.

Earlier talking of the blue foam squares pad, [edited] Franco said, “I did have a thin (maybe 3mm ) Evazote mat but this one is somewhat similar in size but gave slightly better insulation for me.”

After it being pointed out in a holistically logical way that the above doesn’t make sense and likely wasn’t objectively true, later in talking about the blue mat, leaves out insulation and focuses on comfort:
https://backpackinglight.com/forums/topic/mat-booster/#post-3596959

U2 says it better than I can, https://www.youtube.com/watch?v=1XzHlySYR_Y

Those wily, fragile, sensitive, ever chameleon like changing and morphing human egos of ours, anything becomes preferable to admitting to others or self that we are wrong, made a mistake, or the like.  Instead, “they will sing, sing a new song, they will sing, sing a new song.” to “distract, distract from being wrong, to distract, distract from being wrong”  Especially when someone you despise is the one pointing it out. “How long, how long, how long, will we sing this song?”

(Somewhat rare does karma play out in the same lifetime as it was sown in, but we are entering a more hyper sped up cycle…  I’m probably going to attract some similar karma also, since my intentions are not completely pure and completely from Love, though my version of love certainly does contain tough love when it’s needed).

Justin, you don’t understand the physics of heat transfer.  It does not matter what the conductivity of the Tyvek is because it is so thin.  I am not sure why you don’t believe in the insulating value of air pockets.

I only mentioned the moderate conductivity of the Tyvek as an adjunct to the other issues, not as the main issue.  

I earlier explained the main issue to Edward John by an analogical comparison.  Say you made a quilt with large, sewn through square baffles, but only 50% of those baffles have down in them in a checkered pattern like this matt.

When you put that quilt over you, the down filled baffles aren’t going to do you much good because the gaps between them are far, far too large to minimize convective heat loss. You’ll get a little localized insulation, but overall you will be rather cold if it’s below what most bodies can tolerate at resting rate.

I then also said, in this matt’s case, it will be slightly better because an air pad will be on top, somewhat sealing those gaps.  But not completely by any means, and any movement will displace and circulate the semi stilled air within these overly large gaps. Even without movement above, the air will circulate and move around too much because the gaps are just too large. The more the air in those gaps can circulate and/or leak, the less insulation it will provide. Air per a perfectly sealed gap of 1 in thick only provides an R value of about 1, if I remember correctly.  And these are not perfectly sealed gaps to begin with.

I understand the principles just fine. I probably should have mentioned earlier that the conductivity of the Tyvek would take a far back seat to the above, but that’s why I focused on the above when explaining it to Edward John.  

You took one little part out of my various posts, focused solely on that, and said I don’t understand what’s going on.  Rather, most men I have observed, are linear logical, step by step, analytical thinkers (and often with short attention spans), and I’m an odd ball being much more holistic, parallel processor, and systems type of perceiver and thinker (sort of like a man and woman combined into the same body, is how I can best describe it, and that goes for many other things besides.  I see someone cry or tear up from emotional pain or joy, and I almost instantly do similar, and yet I can be as objective and logical as Spock on his best days. A rather weird human that most can’t relate to and can’t relate to most others).

How are you concluding that these air pockets on this mat that was made and used by someone else allow too much circulation?  I started with Tyvek because you spent your first two posts discussing the insulative value of Tyvek… including bolding the insulative value of Tyvek.  You started an argument with some random person trying to show what he did doesn’t work and that argument showed a complete lack of understanding of the physics you were discussing.  You have declared this project worthless and you have no idea what you are talking about.

Hmmmm, no one mentioned loft pockets. Franco should resurrect his design for bag use over an inflatable.  The allowed loft of the 3/8″ of insulation by the alternating squares could be a very good idea.

This is how I used that booster

the whole idea was for the TR mat not to touch the ground but to rest on those tiles and that is how it worked. That was on snow, the effect could be less noticeable on bare ground, I don’t know.

BTW, I’m not claiming this to be anything other than a 110g compact  “mat booster ” that does work.

“How are you concluding that these air pockets on this mat that was made and used by someone else allow too much circulation?”

By looking at the size of the squares in relation to the pad size. Again, even with an air pad on top of most of it, it’s just too much volume of “free air” to be effective “insulation”.  It could be modded to work much better though.

“I started with Tyvek because you spent your first two posts discussing the insulative value of Tyvek… including bolding the insulative value of Tyvek.”

It’s true that my very first post on this thread only addressed tyvek, but there is a larger context involved. My first reply was primarily in response to MJH’s post, where he asked, “Tyvek and foam insulation? I can’t quite be sure what that is made of.”

I confirmed that it was indeed Tyvek, as the foam part was obvious. Note that my first post was pretty brief, unusually brief for my posting style and pattern here. I tend to write a lot when I have the time.  At this time, I didn’t have a lot of time and so wrote a very brief post.

But in my very next reply/post, the 2ND, when I had more time at the time, I also went into the issue with the air gaps being far too large to facilitate effective, efficient insulation.  It is there in the 2nd post for all to see.

“You started an argument with some random person trying to show what he did doesn’t work.”

Let’s just say, there is a multi year history here, and this is not a “random” person, and that this was not a random interaction. There is more going on than what appears on the surface. There is no point is explaining all of what is going on below the surface, and I doubt most here care. But the timing of this thread, was no accident.

And, if it’s for insulation purposes, it really doesn’t work that well.  You’re correct that the Tyvek/moderate conductivity part is a minor variable in this, however, even then, it is a variable, and if we are going for absolutely warmest at least weight, why would we use such a material?  Why not squeeze all the insulation out of the materials that you can get?  

That is how I naturally and automatically tend to think.  How can this be improved, optimized, made more efficient.  But by far, the too large air gaps is the main issue. In hindsight, I realize I should have brought that up first and focused more on that.

“and that argument showed a complete lack of understanding of the physics you were discussing.”

In my last reply to you, I very logically and holistically explained what was wrong with this design.  Please refute it if it is incorrect.  All you had to say was, “How are you concluding that these air pockets on this mat that was made and used by someone else allow too much circulation?”

To me, that is so bloody obvious that I don’t know how I could even begin to explain it to someone who is not understanding.  Look at how large the space between the foam tiles are. Now, if you put some fibers or the like in those spaces, helping to still that rather free volume of air, then one could greatly improve this design. If you actually put this on top of the air pad, and used a sleeping bag, that would greatly help this design.

Otherwise, a foam matt, cut to the size of the air pad would be far more efficient weight to warmth wise.

“You have declared this project worthless and you have no idea what you are talking about.”

I wouldn’t call it completely worthless. If it was modded or used in a different way, like James recently outlined, it could work well.  As to the 2nd part, that is your subjective opinion. Explain to me and to everyone, how those rather large air gaps will provide efficient insulation even with an air pad on top?

That you think that this would provide efficient insulation, indicates to me that it is you that doesn’t understand the principles involved.

Here’s a scenario to illustrate same.  If you have two separate panes of of glass that are sealed, one with say a just a .4″ air gap, and the other with a .4″ air gap + a lot of very fine fibers with a little space in between each fiber (aka “lofted”) which pane, which is otherwise identical, would provide much more efficient insulation?

The very obvious answer is, the latter pane is going to provide the most efficient insulation per same thickness and volume of air gap, and because the air within the pane cannot freely and easily circulate/move around with all those tiny fibers providing a “torturous path” for the air to move through. In other words, it greatly slows down the convective process.  This is why goose down, aerogels, certain foams, etc are such great insulators for their weight.

In the actual case we are talking about, we are not talking about a perfectly sealed gap, so it will be affected even more by the large volume of free air issue.  Any little movement on top of the pad will tend to facilitate even greater movement and circulation of the air below it.  But even if you laid perfectly still on the pad all night, those overly large gap areas would lose lots of heat energy via convection. And meanwhile, why use a material that is moderately conductive?  Polypropylene has about the same density of PE, but has much lower thermal conductivity.  Why not squeeze every little bit of insulation per weight out of a system that you can?

I am not wrong about this, nor the fact that a thin foam pad cut to the size of the air pad, would be far more efficient use of weight and bulk to increase insulation.

I use a plain 1/8″ CCF mat under my Synmat UL7, much like Franco.

Cheers

I would not dream now of using something like that or even a full standard 10mm mat, by itself.

I need way more cushion under my bones than that.

Again , I later opted just for one mat but something like this could be a fun and cheap project for someone that wants a compact and light two mat system.