[Bldg-sim] LEED & Natural Ventilation

Rimes, Christie Christie.Rimes at wspfk.com
Thu Aug 12 15:54:38 PDT 2010

To include natural ventilation in a model all you need to do is fill out the Natural Ventilation Tab at the System level under OA as follows. All inputs have good descriptions of what needs to be entered so you shouldn’t have a problem defining your system.

I am still currently building the model so am not sure if I am going to come up with any errors. 






From: Zhen Tian [mailto:tianzhen9 at yahoo.com] 
Sent: Tuesday, August 10, 2010 10:21 AM
To: Rimes, Christie
Subject: Re: [Bldg-sim] LEED & Natural Ventilation


Hi Chris,

Regarding the natural ventilation in eQUEST, how do we use the S-G function? I cannot find any information in the DOE2.2 manual. Would you please share more information?

Thank you very much.



--- On Fri, 7/30/10, Rimes, Christie <Christie.Rimes at wspfk.com> wrote:

From: Rimes, Christie <Christie.Rimes at wspfk.com>
Subject: Re: [Bldg-sim] LEED & Natural Ventilation
To: "Chris" <floodyc at gmail.com>
Cc: "bldg-sim at lists.onebuilding.org" <Bldg-sim at lists.onebuilding.org>
Date: Friday, July 30, 2010, 2:40 AM

eQuest, TAS and IES, I know can model natural ventilation. In IES and TAS you can actually model the operation of the windows by defining limits on indoor temperature, wind speeds etc. eQuest is a little more basic where you can use a S-G function for infiltration which calculates higher infiltration rates based on outside wind conditions. eQuest then calculates if indoor temperatures will be kept between the indoor temperatures based on the outside conditions. If yes than it will shut off the mechanical system and calculate 0 energy for that hour.


Therefore in programs like IES and TAS you may be able to keep conditions below the set point even if the outdoor temperatures are hotter due to air movement etc. You may also want to come to an agreement with the client to allow a slightly higher set point, however you will need to also apply this to the baseline model. Otherwise for LEED, you can’t take account for the hours were naturally ventilation doesn’t provide comfort. Also note that the unmet load hours can be a maximum of 300 hours so potentially you could take credit for 300 hours for natural ventilation even if it is above the set point.  




From: Chris [mailto:floodyc at gmail.com] 
Sent: Thursday, July 29, 2010 11:24 AM
To: Rimes, Christie
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] LEED & Natural Ventilation


And how did you model the natural ventilation?

In summer when external temperatures are above the room setpoint natural ventilation during the day would not provide any cooling.

On Thu, Jul 29, 2010 at 11:19, Rimes, Christie <Christie.Rimes at wspfk.com> wrote:

I am currently doing a naturally ventilated building for LEED and I believe that if the space is achieving indoor temperatures between the given set point using natural ventilation than the mechanical system energy is 0 for the proposed design. Any hours where natural ventilation can’t achieve indoor temperatures within the set points, a mechanical system needs to be modeled even if there isn’t one in the proposed building. This helps keep the unmet hours within the requirements for LEED.





From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chris
Sent: Thursday, July 29, 2010 11:13 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] LEED & Natural Ventilation




we regularly design and model buildings which rely in part on natural ventilation as a source of free cooling. The issue we are often faced with is how to capture this benefit when performing a LEED Appendix G analysis. Appendix G states that all conditioned spaces must have BOTH heating and cooling. We would like to remove mechanical coolig in the proposed design building and thus gain benefit when comparing to the mechanical cooling system in the reference baseline building.


Has anyone tackled this issue and come to a satisfactory resolution? 


Thanks for your help.

Chris Flood BSc (Eng)
Senior Building Analyst & Energy Modeller

Chris Flood BSc (Eng)
Senior Building Analyst & Energy Modeller

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