[BLDG-SIM] Thermal mass walls
Jeff Haberl
jhaberl at esl.tamu.edu
Tue Jun 24 15:23:34 PDT 2003
Couple of questions:
1. What is the freezer floor? Is it insulated?
2. What are the exterior conditions? Is this freezer in an unconditioned
warehouse?
3. Are you using custom weighting factors or pre-calculated weighting
factors?
Jeff
8=! 8=) :=) 8=) ;=) 8=) 8=( 8=) 8=() 8=) 8=| 8=) :=')
8=) 8=) 8=?
Jeff S. Haberl, Ph.D., P.E.............................jhaberl at esl.tamu.edu
Associate Professor....................................Office Ph:
979-845-6507
Department of Architecture...........................Lab Ph: 979-845-6065
Energy Systems Laboratory...........................FAX: 979-862-2457
Texas A&M University..................................77843-3581
College Station, Texas, USA...........................URL: www-esl.tamu.edu
8=/ 8=) :=) 8=) ;=) 8=) 8=() 8=) :=) 8=) 8=! 8=) 8=?
8=) 8=) 8=0
-----Original Message-----
From: postman at gard.com [mailto:postman at gard.com]On Behalf Of Mark E. Case
Sent: Tuesday, June 24, 2003 3:45 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] Thermal mass walls
Ok - here's a question, maybe stimulate a little controversy but as many of
you know - that's the way I like it.
-10 F freezer, 100,000+ square feet. Reasonably steady product loading 24
hours a day (say 90 tons +/- 25 tons in a given hour).
Two envelope systems: 5" metal skin panel with expanded polyurethane vs.
thermal mass panel of 8" HW concrete interior, 6" extruded polystyrene,
2-1/2 HW concrete exterior.
Polyu conductivity .0142 btu/h-ft-F (LTTR basis). Metal skin wall U without
external skin resistance (DOE2) = ..033. Polystyrene .0167, thermal mass
wall U = .030.
Question - which one is better? That's a loaded question but from a strictly
thermal performance measure - kWh per year to cool - is there more
difference than the .030 vs. .033 U-value would imply?.
We are using eQuest (Doe2.2) and it show the thermal mass as `slightly'
better. The manufacturer, based largely on testimonial evidence, insists it
is MUCH better.
One issue that they raise is infiltration through the metal skin panels and
the impact on in-situ R value. They site ORNL test results that apparently
show this but I've not seen them. I know ORNL did some testing on apparent R
of mass walls but it didn't seem conclusive to me that it would apply in
this situation.
Anyone out there that can cite well documented research about the
differences? Anyone have comments about DOE2's strengths and weaknesses in
capturing the effects of the large wall thermal mass?
Mark E. Case, President
etc Group, Inc.
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