[BLDG-SIM] Software for Modelling Ventilation and Thermal Mass

Vikram Sami VSami at lasarchitect.com
Thu Jun 8 09:49:02 PDT 2006


Kendra,

We recntly did a similar study with the Blue Ridge Parkway Visitor Center in Asheville, NC. The building has a series of Trombe walls, and the initial goal was to do away with air conditioning all together (got pushed aside for reasons I will not go into - I call it the ASHRAE syndrome). 

Anyway, I initially did a study in eQUEST, running the building in free run mode (I think its called LIMITSUM) without an HVAC system, and found that the benefits of the mass were showing up in the model. However, (and as far as I know this is true of energy plus and eQUEST), the model is a 'lumped node' model (an entire wall is the same temperature, the room is modelled as mixed temperature), so you do not get a full-field solution you would with say a CFD model, or RADTherm. For most mechanically conditioned spaces, this is not an issue, since that is what the system is designed to do - mix the air (displacement ventilation being the obvious exception). In passivley conditioned spaces, this is much more crucial, since conditions will vary significantly across a space, and buoyancies & MRT play a significant role in overall comfort conditions. We found in our building that we had significant issues with high MRTs on the Southwest corner of the building - something the other models would not have told us. 

The fact is, most of the building energy simulation tools popular today (energyplus, eQUEST etc) are geared towards calculating the energy consumption of the building - systems and all, and less towards calculation of comfort levels with or without systems. Again, I speak more towards my knowledge of eQUEST rather than my very limited knowledge of EnergyPlus.

Short answer - I would recommend a full-field solution - possibly CFD. 

I would also be interested in others' responses to this issue, as its been one I have been wrestling with for a while now.


Vikram Sami, LEED AP
Direct Phone 404-253-1466 | Direct Fax 404-253-1366

LORD, AECK & SARGENT ARCHITECTURE
Responsive Design · Technological Expertise · Exceptional Service
www.lordaecksargent.com 



-----Original Message-----
From: BLDG-SIM at GARD.COM on behalf of Tupper, Kendra
Sent: Thu 6/8/2006 12:04
To: BLDG-SIM at GARD.COM
Subject: [BLDG-SIM] Software for Modelling Ventilation and Thermal Mass
 
I'm currently working on a project in Berkeley, CA with an underground
concrete building with very high thermal mass.  We would like to avoid
air conditioning by mechanically ventilating the building at night, and
would like to model this for some preliminary results.  

Does anyone have any suggestions for an appropriate software program to
model this?  Are the ground heat transfer/thermal mass modeling
capabilities of DOE 2.2 are sufficient to model this project in eQuest
or Visual DOE?

Right now, we are planning on using EnergyPlus, but I wanted to make
sure there wasn't another (less time consuming option) out there!  Does
anyone know if any of the EnergyPlus interfaces could handle this (i.e.
Design Builder)?

Thank you!

Kendra


Kendra Tupper		
 FLACK + KURTZ	
405 Howard Street		415.398.3833 Main
Suite 500			415.402.5840 Direct
San Francisco, CA 94105		415.433.5311 Fax
http://www.flackandkurtz.com	kendra.tupper at sf.fk.com
 

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