On the science of sleeping mats

Discussion in 'Sleep Mats' started by Jamess, Dec 24, 2016.

  1. Jamess

    Jamess Trail Blazer

    I'm confused. Easily done I know but bear with me.

    If a down jacket works by creating a space around you of air, and it is the air that provides the insulation, rather than the down itself, why would a sleeping mat with down in it be any more efficient than one without?

    Either I've got my science wrong (probably) or mats with insulation are a marketing fad.

    So what is the science?
  2. Mole

    Mole Thru Hiker

    AFAIK, Primarily, the insulation stops air convection currents. In a non insulated mat these currents take the warm air (at the top layer - warmed from your body) and dump it's heat to the cool floor/side walls.

    Try sleeping on a plain non-insulated airbed in colder temperatures. Even indoors I can feel the heat being robbed from my body straightaway.

    R values are a measurable specification?
    FOX160, Lady Grey, Teepee and 2 others like this.
  3. Shewie

    Shewie Administrator Staff Member

    I asked my mate the exact same question a few months ago Jamess, he makes his own gear and understands the science behind a lot of kit much better than I ever will.

    I'd got into my head that down simply "trapped" air, so like you wondered why a sealed chamber couldn't achieve the same result.

    Mole nailed it
  4. Rog Tallbloke

    Rog Tallbloke Thru Hiker

    Yep, it's all about slowing the rate of convection. The down fill helps prevent air currents set up by the temperature differential between warm and cold sides of the pad from forming and transferring your body heat to the ground.
  5. Jamess

    Jamess Trail Blazer

    That explains why the silvered radiator insulation I use on top of my mat feels so effective. It must be reflecting my body heat back onto me and preventing the transfer of my body heat into the pad. Without the circulation the pad will be a more effective insulator from the ground.
  6. Imperial Dave

    Imperial Dave Trail Blazer

    Jamess likes this.
  7. Rog Tallbloke

    Rog Tallbloke Thru Hiker

    Yes. properly closed-cell foam is the most effective. Cheap underlay not so much. Old yellow karrimats are good because they were made in the day when CCF was blown with CFC gases which are effective at absorbing radiation as well as reducing conduction and convection. Not allowed any more, which is pretty stupid considering the tiny amounts of CFC involved.
  8. Jamess

    Jamess Trail Blazer

    Interesting stuff. The weight of the insulated mats is off putting but it looks as though some ccf under my body is worth trying as a cheap experiment.
  9. Mole

    Mole Thru Hiker

    I still have 3 different 'original' karrimats.

    They are warm, solid and durable. But, being dense, they do weigh significantly more than 'modern' ccf mats. E.g. an 8mm 3season karrimor weighs 300g or so - around twice as much as a similar size/thickness multimat camper
  10. Imperial Dave

    Imperial Dave Trail Blazer

    GG thinlight and 2mm laminate flooring underlay for me in the winter :)
  11. Rog Tallbloke

    Rog Tallbloke Thru Hiker

    In recent years I've been using a 3/4 BA clearview as a light and cheap option for summer, with a foil backed 2mm foam 'picnic blanket' as combined groundsheet/insulation under it. For winter I picked up a LW downmat in a sale but 860g! This year I've sold the downmat and picked up an Exped UL7 M in a sale.
  12. Imperial Dave

    Imperial Dave Trail Blazer

    My record with blow up mattresses isnt good so I stick with stuff that is (relatively) indestructible :)
  13. Rog Tallbloke

    Rog Tallbloke Thru Hiker

    Repair kit of PTFE - Plastic Tape For Engineers. :D
  14. Imperial Dave

    Imperial Dave Trail Blazer

    ahhh no I normally manage to completely destroy the valve thing :(
  15. Rog Tallbloke

    Rog Tallbloke Thru Hiker

    Fumsy clucker. :D
    Lady Grey likes this.
  16. Imperial Dave

    Imperial Dave Trail Blazer

    I have to apply the KISS principles to anything I use in the outdoors :)
  17. Toot

    Toot Backpacker

    An interesting thread, folks, for someone with an interest in mat performance.

    Apologies to all if a redirection isn't "kosher" to bring up, but over in the Sleeping Bags & Quilts section this very recent member of Trek-Lite posted a response to a question being asked about improving sleep-mat R-value. Any argument that mention of sleep-mats should be here is already incidental and comparatively unimportant and in any case such an "error" isn't my fault so let's focus on the topic rather than where it comes up.

    In my post, a practice of mat use I initially engaged by way of frustration is mentioned - I put my mat inside my sleeping bag and after two years or so of doing so I remain convinced that this improves the effectiveness of mat performance, ie; I sleep warmer by using this method. I even think I know why this is and mention that too, and it seems to me to follow the KISS principle rather than being rocket-science.

    Thing is, I mentioned this curious habit in that other place to see what minds of greater understanding than mine would have to say about it in comparison with other things being said with mat performance improvements in mind. I don't need a second opinion as to whether or not my method of mat use is a warmer way because practice already assures me that it is - what I'd like to know is if the way I think it works really is the way it works. That's why I'd like to see what the brains here think about it, hence my redirection to where this matter (amongst related detail) appears.

    So, if mat-interested folks have time to wander over there I'd be interested to hear what any "mat scientist" has to say about the topic I refer to - and I repeat, comment that the subject should have appeared in this section of Trek-Lite is unimportant by comparison. I really do look forwards to thoughtful opinion. Ta.
  18. Chiseller

    Chiseller Ultralighter

    Aye me too.... My exped has just expired this morning... Popped it's clogs... Well it's form anyway.
    So it looks like I'm going to have to back to foam unit can afford a brand new one with warranty....
    Now to research the warmest non inflatable mat, unless I can find an answer on here?
  19. Teepee

    Teepee Thru Hiker

    @Chiseller; Thermarest Ridgerest style is about the warmest standalone CCF mat. Z-rest is slightly less warm but punches a little above the also excellent Nato green dual density mats. Z-rest is the comfiest CCF mat I've slept on.
    Chiseller likes this.
  20. Chiseller

    Chiseller Ultralighter

    Cheers, I'm. Proper annoyed /disappointed... Blown all my brass (not worked in over two months with my shoulder) from selling kit on two bivis and the silvertip... Only to have a bit of kit I loved fail when I needed it most... Off. To scratch head, stroke beard.... Have a look in the cellar and check the pricing on your recommended lays. Cheers
  21. Chiseller

    Chiseller Ultralighter

    I'm thinking... Karrimor z lite knock off for 8quid and some silver bubble wrap underneath...or even spray it with some silver spray... That yes it would break up and may attack the foam... But being a lighter colour than the green... Should reflect some heat back up.... Or of the bloke who owes me a refund on a Filson shirt coughs up... Ill fry my head between the ridgerest or the z sol... Comfy can be as good as warmth, especially if it's close between the ratings like it seems... Could always chuck some aluminium bubble wrap under for what it weighs?
  22. Ken T.

    Ken T. Ultralighter

    Anybody have a link to the page Toot is talking about?
  23. Teepee

    Teepee Thru Hiker

    The Karrimor mat is comfy too. Sucks a bit of water though as it's more like open cell foam.

    Some decent prices on foam mats on Ebay and Ali. The Naturhike reflective mats are quite good.

    If you've got acrylic silver spaint and it's water based, it won't melt the foam. :)
    kamov and Chiseller like this.
  24. Chiseller

    Chiseller Ultralighter

    It's only a put me on kind of thing.... I'll sort summat after this weekends bimble
  25. kamov

    kamov Summit Camper

    On a recent 5 day trip I tested the Naturehike folding mat and can confirm that! I also have Thermarest z-lite sol which is heavier, softer and arround 2-3cm narrower. Not sure which one I like more tho, but for the money it's a good choice..
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