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Theory behind thermal insulation

  1. Nov 4, 2011 #1
    I wish to design highly insulating structural load-bearing walls using local materials. Part of that effort requires an understanding of the dynamics of current insulation materials and why some are much higher in R-value while using the same base material. Part of my study so far suggests that there are 4 aspects to consider:

    • The solids conduct as little as possible and that includes using a glass material (supercooled liquid) that has less molecular connections then a crystalline solid and thin strands of material that conduct less based on the cross-section of the strand
    • Stopping the movement of gases as gases have low conductivity but can move heat via convection movement
    • Stopping heat movement via radiation
    • The interaction between solids and gases and especially combinations of different gases that creates reduced molecular interactions

    The interactions of gases in the presence of solids is the part that brings in dozens of laws about gases and molecular science that are what I hope to learn more about. My question is if there are any explanations of thermal insulation that touch on this kind of science that I can read online.
     
  2. jcsd
  3. Nov 4, 2011 #2
    I can not help you with theory, but you may not need it.
    First you may be interested to know that 'load bearing' and 'insulating' are somewhat
    contradictory requests for one material to satisfy. Strong materials are typically
    dense and bad insulators, while most insulating materials are not mechanically strong.
    This ist typically resolved by building the wall from several layers, the strong, heavy innermost
    layer will bear the loads and will also have a great heat capacity keeping the temperatures
    comfortable even under external heat or cold influence.
    The insulating layer will be on the outside, it is made of insulating material and will restrict
    heat loss. The outermost layer will be a mechanical protection, also against weather and will
    provide for nice optics.
    Be sure to arrange materials by decreasing resistance against water vapor diffusion, so
    that humidity can leave your construction freely. Failure to do so will result in wet insulation
    or mold.

    Play with floor, wall or ceiling constructions on the site
    http://www.u-wert.net/berechnung/u-wert-rechner/?cid=o5rzklJB&lang=en"
    you will quickly get the feel for it!

    hth.
    gnasch
     
    Last edited by a moderator: Apr 26, 2017
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