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Far Galaxy
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Posted: Tue Jun 24th, 2008 03:23 pm |
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can someone help me explain the diffence between them?
BTU/hr-ft2-F is the unit for U factor. The rate of heat transfer of a building section.
C-Conductance has the same definition and same unit.
thank you much.
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BlewBe
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Posted: Tue Jun 24th, 2008 03:42 pm |
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The U-Factor is the overall measurement of heat flow through multiple materials, including air space.
C-Factor is the measure of heat flow through a *homogenious* material, at any thickness.
.... I think....
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Disgruntled
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Posted: Tue Jun 24th, 2008 04:18 pm |
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BlewBe wrote: The U-Factor is the overall measurement of heat flow through multiple materials, including air space.
C-Factor is the measure of heat flow through a *homogenious* material, at any thickness.
.... I think....
I would agree.
Typically I think of U-Factor as the overall heat transfer through an assembly. The key is U-Factor includes the air space on each side on an assembly (An assembly could simply be just a 8" concrete wall or more complex).
Thermal Conductance (C) measures the heat transfer from one surface to the opposite surface of a materal of a given thickness. It will not include the air film on either side.
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Far Galaxy
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Posted: Tue Jun 24th, 2008 05:52 pm |
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I thought the Conductance is used on Electrical stuff only...no?
well, anyway, as you can see my "describe me", I was scheduled for this last one this coming Sat, but I freaked out cuz I still don't know what the holly I am studying.
So, paid them $35, move back 1 month. Hope to catch a few more things before the new date.
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BlewBe
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| Joined: | Tue Jul 31st, 2007 |
| Location: | ARC******, LEED AP, Kansas USA |
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Posted: Tue Jun 24th, 2008 06:17 pm |
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| eh... $35 is better than waiting the 6 months to retake (and paying another $102). Keep asking questions though... helps you, helps us.
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Disgruntled
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Posted: Tue Jun 24th, 2008 06:56 pm |
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Far Galaxy wrote: I thought the Conductance is used on Electrical stuff only...no?
well, anyway, as you can see my "describe me", I was scheduled for this last one this coming Sat, but I freaked out cuz I still don't know what the holly I am studying.
So, paid them $35, move back 1 month. Hope to catch a few more things before the new date.
I just started studying for ME this past weekend. I spent the last four days reading Chapter 7 of MEEB (along with the relevant Kaplan chapter). At the rate I'm going it will be 6 months before I'm ready
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LSU
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| Joined: | Wed Sep 27th, 2006 |
| Location: | Washington, Louisiana USA |
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Posted: Wed Jun 25th, 2008 07:50 pm |
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there are three terms at play: conductivity (k), conductance (C), and U-Value.
"k" is material conductance per inch. ex: cement mortar = .5 k (per inch)
"C" is material conductance of given dimension. ex: a modular brick = .8 C
U-Value would be the sum of all the k and/or C that make up the assembly including the surface air film.
at least, that is how I understand it.
edit: also,
for individual component: C = 1/R (Resistance)
for assembly: U = 1/summation of R
Last edited on Wed Jun 25th, 2008 08:06 pm by LSU
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