[Bldg-sim] Internal mass modeling guidance in E+?

Joe Huang yjhuang at whiteboxtechnologies.com
Mon Jan 14 12:44:07 PST 2013


Although we would like to have all building inputs to be well-documented, this is still 
far in the future, especially for those inputs having to do with lifestyle and behavior.  
On internal mass, the proverbial story is to call a moving company and ask how much stuff 
do they haul in a typical move.  I actually had a researcher do that 20 years ago, and she 
came up with a number of 5.5 lbs/ft2  for a residential building.  I see that the Building 
America has upped that to 8 lbs/ft2.  I have no grounds to either believe or disbelieve that.

I've heard even less discussion on the internal mass of commercial buildings.  As the 
original developer of the DOE Reference Buildings, I can say that all those inputs for 
internal conditions (mass, shading, occupancy schedules, etc.) are based on "engineering 
judgment" (at least in my original work)

It's not particularly difficult to survey an appropriate number of houses/buildings and 
come up with something more defensible, but sad to say, nobody wants to support that 
because it's not regarded as serious research.  About 20 years ago, a colleague at FSEC 
and I came up with a Work Statement for ASHRAE TC 4.7 to survey a collection of homes and 
develop prototypical operating conditions.  It got approved but just at the verge of going 
out for bid, ASHRAE Research decided to withdraw it.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"


On 1/14/2013 12:16 PM, Qinpeng Wang wrote:
>
> Dear colleagues,
>
> I'm looking into furniture/internal mass modeling in energy models particularly within 
> the environment of EnergyPlus but also not limited to that.
>
> I have two questions I guess:
>
> 1, Are there any modeling guide or reference building report that may give 
> recommendations/instructions on how to represent furniture/internal mass inside a 
> building if there is no much detailed information? I guess all I'm asking is are there 
> any published data-set, or default values in terms of material property and area to 
> represent furniture like what could be easily found about schedules and occupancy density?
>
> COMNET modeling guide has only one paragraph about it and it mentioned "The interior 
> thermal mass and modeling assumptions in the baseline building shall be the same as the 
> proposed design."
> Currently what I have is from Building America House Simulation Protocols: "The internal 
> mass of furniture and contents shall be equal to 8 lb/ft2 of conditioned floor space. 
> For solar distribution purposes, lightweight furniture covering 40% of the floor area 
> shall be assumed."
>
> 2, DOE reference commercial buildings have internal mass objects in the idf. file, where 
> does the information come from?
>
> Appreciate your input!
>
> Best,
>
> Qinpeng
>
> -- 
>
> Qinpeng Wang, PhD Student
>
> College of Architecture
>
> Georgia Institute of Technology
>
> Atlanta, GA 30332-0155
>
>
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