Re: [EnergyPlus_Support] Insulation

[David Scheer <david@xxxxxxxxxxxxxx>]

It is much simpler and more complex than what you are asking for, and I would be very VERY careful to not get distracted by 'R' values.  You need to remember your basic heat flow equations (k, C, r, R, U), not the abstractions that materials suppliers communicate to contractors for simplicity (Rvalue).  

The material example you show is valid for any Rvalue, all you have to do is change the thickness.  If you want to change the Rvalue without changing the thickness, you have to use a different material (ie conductivity, density and specific heat).  Most materials you will ever use are listed in the ASHRAE HOF.  Remember, Conductance (C) is the inverse of Resistance (R), and C is dependent on c and thickness.  Also don't forget bridging effects of framing, etc.

Wikipedia's entry on Rvalue has some interesting tidbits about how the commercial Rvalue number has been twisted and abstracted.  In E+ we are workikng with first principles, not politicized commercial product ratings.

If you want to do it more simply (with the understanding that it may not match what can really be built), just use a simple material-R, where you can specify Rvalue directly.  Insulation usually has little mass to affect the heat balance dynamics, so that shouldn't effect your simulation much as long as you have mass in other areas of the zone and/or layers of the insulated construction.

David

On Fri, Jul 3, 2009 at 4:36 PM, Linda Lawrie <linda@xxxxxxxxxxxxxx> wrote:

Look in the datasets folder
"ASHRAE_2005_HOF_Materials.idf"

The Output Details document describes the files in the DataSets folder.

The example files may contain really old definitions from both DOE-2.1E and
BLAST.

EnergyPlus Development Team

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