[Equest-users] Natural Ventilation Only

Ng, Lisa lisa.ng at nist.gov
Mon Apr 18 05:22:44 PDT 2011


Christine,

What result are you looking for with the natural ventilation – air change rates, sizing of openings?


If you want air change rates, CONTAM is an airflow simulation tool available at no charge from NIST http://www.bfrl.nist.gov/IAQanalysis/. It performs a multizone analysis of airflow, i.e., each zone is “well-mixed” and has one temperature, airflow rate, etc. Currently, temperatures are scheduled inputs. If you want indoor temperatures to be calculated/updated as a result of natural ventilation, EnergyPlus is available at no charge from DOE http://apps1.eere.energy.gov/buildings/energyplus/. There is an “Airflow Network” capability that does almost the same things as CONTAM (use the “MultizoneWithoutDistribution” option). The Airflow Network capability in EnergyPlus is implemented by a text file whereas CONTAM has a GUI. CONTAM can output building air change rates for every time step. I believe EnergyPlus can output an average air change rate for each zone. To get air change rate for each time, I believe you’d have to calculate it based on available outputs.



If you want to size openings, NIST has another tool, LoopDA also available at no charge http://www.bfrl.nist.gov/IAQanalysis/software/LOOPDAdesc.htm. It’s basically solving the “inverse” problem.



Lisa





From: McArdle, Mike [mailto:Mike.McAardle at state.vt.us]
Sent: Friday, April 15, 2011 5:05 PM
To: 'Bruce Easterbrook'; Rimes, Christie
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Natural Ventilation Only

Another method wd be to manipulate the infiltration values which are based on building pressure differentials ie wind affected.


Thank you,  Sincerely,

Michael J. McArdle , P.E.
Buildings Engineer II, Project Manager
State of Vermont,
Buildings and General Services (BGS)
2 Governor Aiken Avenue
Montpelier, Vt. 05633

Office: 802-828-5650;  cell: 802-272-4828

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bruce Easterbrook
Sent: Friday, April 15, 2011 5:02 PM
To: Rimes, Christie
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Natural Ventilation Only

Building codes and ASHRAE 62.1 which most codes reference requires the outside air to be based on building square footage and the number of people in the building.  See the app G economizer discussion currently going on.  Your design needs to guarantee your system can deliver the fresh air required and not depend on whether the wind blows or not.  One thing you might investigate would be to use exhaust fans to meet this minimum flow.  Also, some codes allow for no mechanical ventilation if there is an operable window of a certain size in the room but this only works for the perimeter of a building.  eQuest is used to model mechanical systems, I'm not sure how well it would work on passive systems.  From what I have read on discussions on this list it doesn't totally mimic the stack effect either which would probably be critical in a passive system.
Bruce Easterbrook P.Eng.
Abode Engineering

On 15/04/2011 03:06 PM, Rimes, Christie wrote:
Hi,

I wanted to create a model in eQuest that only had natural ventilation using the S-G method and no mechanical system. Is this possible?
I have come up with the following problems:

I have used a PSZ unit and have 0 cooling capacity, no ventilation requirements and not installed heating – however I am still getting cooling and fan energy

If I turn off the fans then the unmet load hours are not calculated as they depend on when the fans are scheduled

If I use a heating only system, natural ventilation inputs are not allowed

I don’t want to just use an economizer for natural ventilation as I want the outside air to be dependent on the wind speeds and not forced with fans.

Any thoughts?

Christie Rimes, LEED BD+C
Designer
WSP ▪ FLACK + KURTZ
405 Howard Street, Suite 500
San Francisco, CA 94105
Direct: 415.402.2727 | Main: 415.398.3833
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