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insulation
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Posted by: frank78

04/20/2004, 01:17:07

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I am doing a project about heat transfer in a house.  I'm confused as the thermal conductivity of the insulation batts is 0.04,  which is higher than the thermal conductivity of air at 0.026.  This doesn't make sense because the purpose of insulation is to slow down heat flow,  so shouldn't it have a lower K than air?  Can someone please clarify this for me,  thanks.






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Re: insulation
Re: insulation -- frank78 Post Reply Top of thread Forum
Posted by: RandyKimball
Barney
04/21/2004, 21:45:40

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In simplicity, generally it is the trapped air or other inert gas (or vacuum) that provides the insulation value in most insulations. Therefore air is the control value and the various other materials that perform the shaped container or the trapping will transfer heat faster than pure air. If we were to only use trapped air, however, the heat would easily radiate to the next surface, (not so good) much faster than it would transfer via "conduction" or convection. So we tend to use substances in a configuration that traps lots of air while it blocks direct infarred or radiated heat(line of sight), as best we can. Thus spun glass, shreaded paper, foamed poly., ... or gasses trapped between layers of glass with various relfective coatings to trap and/or redirect infarred or radiated heat.
-I hope I didn't muddy the water too much..
-randy-



The worst suggestion of you lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

Modified by RandyKimball at Wed, Apr 21, 2004, 21:54:29

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